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Before yesterdayHam Radio - QRP

Begali Intrepid

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
11 May 2023 at 01:34

 The Perfect Bug?

In the Western World we are consumers.  Advertising drives us to think we'd be a bit happier if we had that new "thing", whatever the thing is.  It drives much of our economies and unfortunately keeps many burdened in debt.

That's certainly a pessimistic way to begin this but let's be honest.  No one needs a ~$580 morse code key.  Most of us are handy enough to make a straight key out of stuff laying around the house for free.  I have a number of very fine keys that I've purchased used. I've purchased most of them for well under $70, including my 1970s Standard Vibroplex Bug.


BUT... If we are ham radio operators regularly doing CW, then we spend a lot of time with a morse key under our hand.  I've said this previously, but when you are a CW operator you touch your key more than anything else related to the hobby.  You are moving it many hundreds to thousands of times as you send code.  Your keying becomes part of you and you are intrinsically linked with the ease or difficulty of operating the key for hours at a time.

So...  having a key that is easy to operate; a key that disappears under your hand is an enjoyable thing. 

Operating a Bug correctly, or more precisely in a manner that is pleasing to the person copying your code is more difficult than operating paddles with an electronic keyer.  When the bug was invented it was a tool used by professional telegraphers.  There were no electronic keyers, and having a tool that allowed them to send good code for hours on end with less mechanical stress on their bodies than a straight key was important, and they sought the best tool they could afford to allow them to do their work.

But no one reading this is a professional telegrapher, because that ship has sailed.

For those of us that choose to use a Bug, we do so for different reasons.  For me, I enjoy the control I have in forming my characters, as well as the extra level of difficulty in sending good code.  Why would I want it to be more difficult?  Well, why do we do anything that is challenging.  Being challenged is fun.  It drives me to improve.  It takes my mind off of things that might otherwise crowd my thoughts if I were not doing something challenging that is also fun.

I have operated a bunch of different bugs at my club gettogethers, from different makers.  They all have a different feel.  They all intrigue or annoy their user.  I have two Vibroplex Bugs at my station.  I've previously written about them.  They each have advantages and challenges but they share the same design and they have more in common than they do differences.

A New Design

Fortunately for amateur radio operators there are still new keys being developed, and in this case a new design for a semi-automatic key that has a markedly different design from most of the bugs that came before. 

The Begali Intrepid is distinctive in a few ways:
  • The pendulum hinge is at the rear of the key rather than the middle
  • The adjustments are all based on magnets rather than springs
  • The dwell for the dits has a real control, rather than using various pieces of foam, string or clips to change dwell time
  • The dit contact is a sprung plunger that always remains centered on the contact rather than brushing against it at various angles
  • The split lever mechanism operates at the center of the key placing the DAH and DIT contacts much closer to one another than a traditional bug
  • There is less mass in the pendulum itself than a Vibroplex Bug
  • It has a sprung, nylon wheel damper that doesn't clatter
  • It weighs a TON (well about 6 lbs) and feels welded to the desk without having to use non-slip material or using spit to semi glue them in place (yech, yes I use spit to hold my keys to my desk)
These differences really add up to make a semi-automatic key that feels markedly different than all other bugs available to amateur operators.

I've not had the chance to try the GHD fully automatic bugs, nor their bugs that use optical contacts.  That would be interesting, but they still fundamentally follow the Vibroplex model.


Preparing for Use

The Intrepid ships with a cable but there's nothing to plug it into on the key.  It's up to the owner to solder the connections.  I understand that some transceivers require different plug wiring but in general they are fairly common.  Be prepared to spend some time soldering under the key to wire it up.

I had some spare 1/8" plugs for projects, and with some heat shrink tubing and a couple pieces of wire I created a tidy connector for the male to male cable shipped with the key.


In Use

I spent about 2 hours practice sending into the practice oscillator that I built.   I had a Vibroplex Deluxe Bug next to it that I alternated with.  The range of DIT speeds on the Intrepid is impressive.  Other makers like Vizkey have created bugs with a similar range of adjustment, and the Deluxe Bug I use has a Vari-Speed that can match the Intrepids speed range, bu the Intrepid is easier to quickly adjust and more importantly can be done one-handed.  It will comfortably go from about 15 wpm up to 35 wpm and with the dwell adjustment makes changing speeds and keeping the DIT dwell correct, is singular.  I don't think any bug can match it in that respect.

It did require a change in how I operate.  The Vibroplex Bug fingerpieces stick out further and I have the habit of placing my index finger out over the top of the Bug.  The Intrepid doesn't allow for that.  I have to curl my index finger down to avoid hitting the bracing for the pendulum.

Because there is less mass in the pendulum it operates with a much lighter touch than Vibroplex Bug.  The pendulm movement is initated with less force and due to the isolation of the pendulum from the paddles you don't feel the pendulum moving as you do with a Vibroplex.  I kinda like the feedback I get from Vibroplex pendulum.  The Intrepid feels more like a single paddle key with an electronic keyer than a bug.

Because of the how the lever is split in the middle, the actual DAH contact is almost dead center in the key rather than toward the front.  It is far closer to the DIT contact than a bug.  I have no way to describe it other than to say it feels as if the DAH and DIT operations are more similar than they are different.

I tend to pivot at my wrist when I operate a Vibroplex bug, to control the timing of DIT to DAH transitions.  That doesn't seem to be as necessary with the Intrepid.  Again, it feels more like a paddle than a Bug.






The DIT contact is a sprung plunger that is always centered.  This is one of the biggest problem areas on a Vibroplex Bug and Begali has masterfully designed the proper contact.  Most Bug operators spend more time adjusting the U-spring to try and get proper contact than any other part of the key.  I assume this level of precision is just not something that Vibroplex wanted to spend the time on in manufacturing.


You'll notice there are spare holes.  I assume they are to allow the frame to be used for left handed operation.

The sprung teflon damper makes for clatter free operation.  No more ker-thunk as you transition from DITS to DAHS.  They key is markedly quieter in operation than any other Bug I've tried.  The only other key that comes close is the right-angle Vizkey.




The weights are easy to adjust but I have found that the set screws don't bite the pendulum as firmly as a Vibroplex bug and I have had them come loose a few times. When they accidently come loose they flop to one side and touch the frame, completing the circuit, resulting in a continous carrier. I'm a bit concerned about leaving the bug connected unattended to my tranceiver and having one flop over into transmit while I'm not at the station.


The laser etching is nicely done.  The model name can appear, white, gray or black depending on the angle of light.





The pendulum is hinged at the back of the key, making easy access to the adjustment weights.









Conclusions?

This is a very fine piece of engineering.  It will take me months to decide if stick with it over a Vibroplex Bug, but for now I'm thinking it was a fine birthday gift.





That's all for now

So lower your power and raise your expectations.







Yaesu Interface Cable SCU-28

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
25 April 2023 at 01:28

 TX Relay, Power and TX REQ IN

R&L Electronics sent me a SCU-28 10-pin DIN cable by accident and were nice enough to let me keep it.  Consider shopping from those guys.  They offer great communication and good prices.

This cable is typically used to wire connections for an external amplifier.  I don't have an external amplifier but I wanted to make use of the +12v power and transmit relay for the protection relay I built for my SDR-Play a few years ago.


I had also read that the TX REQ IN pin could be used to switch the radio into a lower power tune mode for use with external tuners. The absence of a TUNE button for external tuners is one of my pet-peeves about the FT-DX10 so I was excited to have one.

Wiring the Break Out Box and TX-REQ-IN

So I used my last spare plastic project box, some female phono jacks and found a push-button that I'd cut off of some other project in my junk box and went to work.


I used some shrink wrap for the momentary switch for the TX-REQ-IN pin.


I wired up 3 phono jacks... One for the TX relay, another for the +12v out, and one for the ALC control in case I ever do get an amp.  I safed the other wires for future use inside the project box.


Partial Success

I connected the box and verified that I was getting power for the relay and that the Relay Switch operated



Unfortunately, the TX-REQ-IN does NOT do what it does with other Yaesu transceivers.  Pressing the button grounds the TX-REQ-IN - the radio does transmit a carrier in any mode (here I tested with LSB) but rather than transmitted a reduced power carrier as it's supposed to, it just transmits at whatever wattage the mode is currently set to.  In this case I had the power set to 50w into a dummy load and it transmitted the full 50w rather than a reduced power 10w or 20w carrier for tuning.  See the power out on the radio's display


In my opinion Yaesu screwed the pooch on this one.  I don't see any reason why they wouldn't operate like they do with their bigger brethren radios when the TX-REQ-IN is grounded.  Some subsequent forum searching turned up posts from others that confirmed that the FT-DX10 does not properly respond to that signal.

My Elecraft KX3 and Ten-Tec Eagle both have a "TUNE" button that sends a low power tuning signal regardless of what the current power setting is at and there's no reason that the FT-DX10 shouldn't do the same.  Having to dive into a menu to change the power setting for tuning an external matching unit is just silly in this day and age.

I have confirmed that my box is working the relay properly to my SDR-Play.  I reference the relay I built to protect the front-end of the SDR-Play in this post https://www.hamradioqrp.com/2017/02/spruce-up-basic-transceiver-with-sdr.html

That's all for now.



So lower your power and raise your expectations




Portable Ops in Comfort

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
16 April 2023 at 23:34
Towable Shack

Working my rolling shack portable station from air-con comfort


We've had a few RV's over the years, but for some reason I've never thought to operate from inside the RV.  I have always tossed a wire over a tree and operated from a picnic table or from my camp chair, as here...




But I thought, "Hey, I have a 12v power supply built-into the RV and the built-in ladder makes a nice solid mount for an antenna mast."

Early try with a military fiberglass pole mast

Now I use a Flagpole Buddy with a 30 foot telescoping mast


Here's a link to the flagpole buddy... link

Our RV has a Converter / Inverter with a spare 25 amp 12v circuit.  I tapped into that and ran a power pole wire to the dinette table.  

The camper had a coax outlet to watch a TV outside the camper... that's obnoxious.  So I cut the cable TV coax and crimped on a UHF connector, and ran that to the dinette table.  I simply attach my coax from outside the camper to cable TV coax adapter to get the antenna connection inside the camper.  Wallah, coax through the wall with no drilling. The cable TV coax run from the dinette to the wall outlet is only a couple feet so it's not really impacting the impedance of the coax run to the antenna.

I've tried a couple of antenna's and have settled on my end-fed 44 foot wire fed with a 9:1 balun and some clip on radials.   I pull the antenna wire through top end of the telescoping mast with kite string, counter-weighted with a heavy sinker.  That keeps the wire taught from the end-fed point up to the top of the mast and out at an angle.

Gone RF fishing with a 30 foot pole and a big sinker.


The Elecraft KX3 and Ten-Tec Eagle will both match a bent spoon with their auto-tuners and have no trouble with the end-fed on 40m and above. 

For a portable key I use my Palm Radio Single paddle.  Either magnetically attached to the steel side of the Eagle or just held with one hand while operating with the KX3.

Palm Radio Single Paddle

On the Eagle the Palm Radio Single magnetically attaches to the side

One thing I find interesting about operating while "camping" (if you call towing a small house to a campground camping) is that I seem to also work a suprising number of other stations that are operating from a campground.

Note the power and antenna connections under the table


The KX3 can stay on the dinette and doesn't take much room.  Keeping the footprint small and the earbuds in, keeps the XYL happy when operating during an outing.

I worked a number of stations on 40m, 30m, 20m and 10m this weekend.  It's always fun to tell a station that you are portable, even if you are essentially operating in your home away from home.


Thats all for now.

Lower your power and raise your expectations

Rich AA4OO HamRadioQRP.com

Benefits of the Yaesu XF-130CN 300 Hz Crystal Roofing Filter

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
5 April 2023 at 11:41

Do You Need That Filter?


The Yaesu FT-DX10 comes standard with a 500 Hz crystal (xtal) roofing filter, but offers an optional 300 Hz roofing filter.  Should you purchase the optional filter?

The 300 Hz roofing filter is twice the size of the 500 Hz filter so it must be twice as good right?  

If you casually switch back and forth between the two filters on a noisy band, it sounds like the 300 Hz filter markedly improves selectivity and quiets the noise.  But try this: Select the 500 Hz filter and narrow the bandwidth (using the bandwidth control) to 300 Hz, then switch to the 300 Hz filter. 

When you digitally narrow the bandwidth of the 500 Hz filter to 300 Hz you will "hear" the same reduction in noise as you have cut out 200 Hz of higher frequency sound.  Engaging the 300 Hz filter lowers the volume a bit (3-6 dB) due to insertion loss.  

So what you are actually "hearing" when you switch back and forth between the filters without changing the digital bandwidth is the reduction of the higher frequency noise that can be accomplished using the bandwidth control alone with the 500 Hz filter.

So, from a selectivity standpointthe 300Hz filter doesn't gain you anything over using the digital filtering with the 500 Hz filter.  The real benefit should come in the form of adjacent signal rejection.  So let's look at that.

In the video below I demonstrate the signal rejection of a 40 dB over S9 adjacent signal to a weaker S3 - S5 signal.


From the video you can hear that there is a very small demonstrable difference in strong signal rejection when using the 300 Hz optional filter, but the difference is so small that I doubt many of us would find practical benefit over simply narrowing the DSP bandwidth while using the 500 Hz filter. Even when contesting.  The digital filtering built into the FT-DX10 is really, really good when using the included 500 Hz roofing filter alone.

Yes, I spent the $200 for the optional filter thinking it would help, but I wished I had known what I do now.  I would have $200 for some other nifty radio gadget to spend instead. 


That's all for now.

Lower your power and raise your expectations

Richard AA4OO

https://www.hamradioqrp.com

Yaesu FT-DX10

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
26 March 2023 at 20:46

Shiny new Rig -- Yaesu FT-DX10

I ordered my FT-DX10 from R&L Electronics this week, along with a 300Hz Yaesu Crystal filter from Ham Radio Outlet, because R&L didn't have the crystal filter in stock.  This is my first order from R&L and I'm happy with their communication and slightly lower prices than the major equipment providers.  They also included an R&L Electronics branded 30A 12v supply for only $40, and I always seem to need a separate power supply.

FT-DX10 next to the KX3


Initial Impressions

It has been over 12 years since I used a Japanese brand transceiver.  Compared to the Elecraft KX3 and Ten-Tec Eagle the FT-DX10 has a higher level of fit and finish.  The case, buttons and switches have a high grade feel.  

I had previously not been able to physically see one of these radios and if I had I may have passed due to the way you physically interact with the radio. The button placement is decidely cramped.  Even though the KX3 and Eagle have significantly smaller front pannels, they both have good spacing between their buttons and knobs compared to the FT-DX10.  All the front panel space used by the FT-DX10's large display definitely reduces the space for physical controls.  

I probably touch the AF/RF knob more than any part of the radio.  It is small.  It is slightly smaller even than the AF/RF knob on the compact KX3, and much smaller than the control knobs on the Eagle.  It's proximity to the VFO has resulted in me accidently moving the VFO off-frequency multiple times.  I would have preferred Yaesu have a smaller VFO knob to make more room for the physical control surface.

Related to the "cramped" controls, I find myself regularly locking the VFO on this radio.  I've never needed to do that on another radio and it's a bit frustrating.  I'm assuming I will become more familiar with the placement and reduce my incidental presses with practice.

In Use

Audio

The audio from the built-in speaker sounds okay on SSB but is very muddy on CW.  I tried playing with some of the EQ controls but I think the large cabinet space under the speaker is just creating a bit of a CW echo chamber at the 450Hz frequency that I like to listen to code at.  CW output at a higher frequency doesn't have the muddy problem but I've developed a painful sensitivity listening CW at higher frequency.  I'm now using an old Vertex mobile speaker on top of the radio and that has cleaned up the CW audio.

Similarly, when using headphones I hear a lot of high frequency hiss even when the audio is turned completely down.  It requires an in-line resistance (outboard volume) or use of higher impedance headphones to eliminate the hiss.  I know a lot of older hams have lost much of their higher frequency hearing but I'm not there yet.

The "sound" of CW from the radio when gain levels are properly managed and the digital noise reduction is employed is quite nice.  It is MUCH better than the audio of the Elecraft KX3 but still not quite as good as the audio from the Ten-Tec Eagle.  The only thing I can say about it is that it sounds less musical than the Eagle.  At some point I will hook up an audio scope to both and compare the audio waveforms.  For now I don't mind listening to it but I haven't had the chance to spend hours listening.

Button mashing

I was concerned about how many times I would have to enter the menu during operation and so far I'm fairly pleased.  There are physical buttons for most of the functions I want to perform during a QSO.   I had considered buying the less expensive FT-710 rather than the DX10; but the MPVD (Multi-Purpose-VFO-Outer-Dial) on the DX10 provide a lot of value by having an additional control ring.  By having both a function knob tied to one of a dozen different functions, as well as being able to assign a function to the MPVD I find that I don't often have to go into the menu.  

Compared to my Ten-Tec Eagle it is easier to operate because the dual-use buttons on the Eagle are perpetually in the wrong mode for me.  Compared to the Elecraft KX3 it is about on-par usability wise.

I wish it had a dedicated knob for power but I understand that I am likely in the minority of people who start nearly every QSO at QRP levels then raise power if needed. Speaking of QRP, 5 watts is as low as the RF power can be set.  The Eagle will go down to one watt and the KX3 will go down to 1/10 watt.  

I am still a little confused about the APF (Audio Peaking Filter) functionality.  The button goes through 2 presses in CW mode and the second press seems to do something different but I'm unsure what that is.  The manual doesn't mention a second press.

The APF is not as effective as the APF on the KX3 at pulling out a weak signal, but the KX3's APF is very strong and makes the signal sound weird.  I don't normally leave it on.  The FT-DX10 APF doesn't negatively impact the sound of the signal but doesn't pull it out as much either.  Mabye there's something else in the menus I haven't seen yet.  

Features

FT-DX10 DNR (Digital Noise Reduction / as opposed to 'Do Not Resuscitate') works very well on CW.  It works much better than the NR (Noise Reduction) on the Eagle or KX3 for CW.  You have to play with the different DNR levels on any particular QSO to find the right match, but once you do it works very well.  I don't think it works as well on SSB as the NR on the Eagle, but blows away the NR on the KX3 on SSB.

The display, ah yes the display.  The display is large and colorful.  I tried using the 3DS (Three Dimension Waterfal) for about 30 minutes and while it is mesmerizing I don't find it as useful as the standard veritical waterfall.  In particular, when there are static crashes the historical 3D waterfall image creates a tall "wall" that makes it very hard to see the signals before and after the static crash.  Since we've had a lot of thunderstorms in the surrounding states (on Thursday evening one storm was producing 443 strikes a minute) it makes that 3D waterful useless.  

The standard waterfall is quite useful although precisely selecting the signal with you finger is very hard, so the mouse needs to be used.  

The internal tuner is matching all the bands on my 80m Windom including 30m which, according to my Elecraft W1 meter is 5:1.  It shouldn't be able to perform a match on that since it's advertised as a 3:1 tuner yet it's working.  YMMV.

The CLAR RX/TX (Clarifier) is what everyone else calls a RIT and it works very well.  When pressed the MPVD ring makes adjustment quick and easy and it both lights up the button as well as has an indication in the display so you don't forget it is engaged.

The ZIN (Zero In) is essentially the same feature as the SPOT function on the KX3 and it works very well to automatically zero beat a CW station.  I think it actually works better than the KX3's SPOT.

I haven't had need to work Split operation with it yet, but it has a button labled TXW which is a momentary button allowing you to listen to the transmit frequency which I think is nicer than having to swap the VFO's back and forth like I do on the Eagle.  However, it's not quite as spiffy as the KX3 allowing you to hear VFO A in one ear of your headphones and VFO B in the other.

As far as standard memories, its operation is a bit disappointing.  My Eagle and KX3 store both VFOA and VFOB frequencies when I save a memory, but the DX10 is only saving the VFOA frequency.  On the other radios I like to quickly jump up to SSB by simply pressing the VFO A/B swap but here I have to store that as a different memory.  That seems like an oversight, so I'm probably doing something wrong.

Nits

My biggest dislikes so far are related to how noisy it is in CW operation.  The T/R (transmit/receive) relay is very noisy.  Not in the same clacky league as the Heathkit HW-101 but still very noisy.  In full QSK it sounds like an old school typewriter in the radio.  My KX3 has silent PIN-Diode switching and the Eagle has a very quiet relay, nearly silent, so to hear the clacking doesn't put me in a happy place.  I've sinced changed my normal full break-in use to semi-break in and lengthened the timeout to 500ms.  I really, don't like that.  I do very conversational CW and like to hear the other station wanting to break-in or hear if I've accidentally infringed on someone.  I feel like I'm keying a repeater.

The other noisy thing is the fan.  The fan comes on even when not transmitting and it's quite noisy.  Compared to the Eagle which has internally baffled fans that you never hear and the KX3 has no fans at all; it creates a much noisier environment.  I wish they'd placed the fan inside the chasis like the Eagle so that it wasn't so loud.  I understand that again I'm in the minority.  Most operators are used to nosiy relays and noisy fans or have an amplifier running that sounds like a Window Air Conditioner, but I'm used to a very quite operating environment.

Headphone use would mitigate both the noisy relay and fan noise but many times I'm just doing casual operating and listening through the external speaker.

It has an "external display" connector to go to an external monitor but the resolution is 800x640.  That's like early 1990s monitor resolution.  Anything bigger than a 15" external monitor results in a great deal of pixelization on the display.  They could have upscaled the display to eliminate the pixelization which would make the external display looks less cheesy.

CW Decode works, sorta.  The radio was advertised as supporting CW decode.  The decoder covers up the waterfall and you have to exit decode to see the waterfall.  I do use CW decode on the KX3 if I'm trying to get a DX station that is sending his call at over 30wpm, and the KX3 displays about 12 characters of information while leaving everything except the VFOB frequency visible.  It's very useful on the KX3 and quite accurate.  The decoder on the FT-DX10 shows paragraphs of decoded CW.  I just want it for a quick assist, not to read 30 minutes of ragchew content from two ops.  The other issue with the DX10 CW decode is that you have to set the CW speed in the menu to match the speed or the accuracy is really poor.  Most decoders just figure it out.  Even the ardruino decoder I built works better. I just wish it displayed a single line in the bottom of the screen.

While we're on CW, it has a CW "memory keyer" function but you have to display the menu and touch the screen to send a CW memory during the QSO.  The memory keyer menu covers up most of the waterfall and going into any other menu function makes the "contest keyer" disappear.  There is a FH-2 keypad that I believe operates without having the menu displayed.  It's a very pricey $100 for a box with buttons connected to different resistance values, so I'll probably build one.  For now I'm using my external memory keyer, which also allowed me to have my manual keys in series with the external keyer output so I can use both mechanical keys and my paddle at the same time.

My KX3 has two key inputs and so does the Eagle, so while I knew the DX10 didn't have two key inputs it is still something I'd miss if I didn't use an external keyer.

Lastly, this is a NIT for me but I can't find anything on the interwebs that says other people have this issue.  I cannot get the radio to reliably interface with OmniRig.  I use OmniRig to interface my radio with Log4OM and other software.  I have searched and searched and others are not having this issue.  I am using the most recent FTDX10.ini configuration file for OmniRig and have it configured with the same serial port settings that work with N1MM (38400, N, 8, 2, Handshake, Low).  It is perplexing.  OmniRig continuously loses connection to the radio.  So this is likely some local PC / software problem I have that I shouldn't blame the radio for.  I even performed a full reset to no avail.

Conclusion

This is the first new HF radio I've ever purchased.  I've been licensed to use HF bands for about 16 years at this point, but I've only owned 6 other HF rigs in that time; all purchased used.  I've owned a number of Yaesu VHF mobile and handheld radios but only one HF and that was the FT-857D.  The FT-857 was a good, portable HF/VHF/UHF radio but due to the limited front panel space and very early DSP implementation was really on the struggle bus when used for HF.

For me this was a very expensive purchase.  So expectations are high.  I knew it was missing some features my other radios already had but I'd hoped the shiny display would make up for it.  At this point it's a mixed bag.  I do like the DNR very much and I can get clean sounding audio out of it using a external speaker, but that's about the only positive.  The clacky T/R relay and noisy fan are a major Debbie Downer at this point.

I know that since I'm primarily a CW operator most of the issues are unique to CW.  If I used Digital modes or did a lot of SSB I'd probably be thrilled with this radio.  If I can figure out the rig interface problems I may try some digitial modes again and maybe it would seem more shiny.   (I know I use the word "Shiny", a lot... It's because there was a Sci-Fi Series on a decade ago called Firefly. The chief engineer used that word for anything she thought was cool or nice... I have sort of adopted it)

I'll give it some more time and see how it works with weak signals.  So far, I've only made a few dozen contacts and less than a dozen extended ragchews due to lots of lightning in my area.  It's really a toss-up at this point as to whether the shiny stuff outweighs the musical audio, and slent operation of my Eagle.



That's all for now.

Lower your power and raise your expectations
73s Richard AA4OO

GAS is Rearing its Ugly Head

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
21 March 2023 at 01:19

 GAS - Gear Aquisition Syndrome

I have some excellent radios.  I have a KX3 that does everything including ironing my pants (well almost) and a Ten-Tec Eagle that has the smoothest CW anyone could ever want.  I also have old crumugeonly radios that require the patience of Job to operate.  I've been well pleased with my collection of RF generating and receiving gear for quite a while.  However, my Eagle is showing its age.  I had to recently replace its T/R relay and the encoders need some cleaning, but it still sounds beautiful.

The problem is these newfangled rigs with their dang, pretty front panels providing information overload with aluring displays of 3D waterfalls and teleporter controls (maybe I mis-read that last one in the specs).  Many of my QSOs now are with operators that have shiny new rigs.  It's just not fair that I'm staring at a segmented LCD display... or in the case of my GRC/9, the front panel equivalent of a Slide Ruler.

The GRC/9 has the operating interface of a Slide Ruler
but wow it's fun to operate... slowly and noisily

The KX3 interfaces wonderfully to my Computer
but it looks dated

Surely ham life must be better when I can gaze at the equivalent of a smart phone on the front panel when using the oldest operating mode known to man?

The Genesis of "Want More"...

In preparation for the upcoming camping season in our RV, I wired a spare 12v 25A circuit in the camper's inverter to bring 12v rig power to the dining table, and co-opted the 75ohm cable running to the cable TV output outside the camper for watching TV (why would anyone watch TV outside the camper).  That cable TV output now takes my antenna connection out of the camper without drilling any holes.  I bought a stellar thing called a "flagpole buddy" to hold my 30 foot telescoping mast on the ladder and wallah, I have a portable Ham shack.  I was using my Ten-Tec Eagle on the dining table, and my wife was not-enthused with having half of the dining table consumed by my bleeping radio. I assured her I'd set it on the seat when not in operation, but I still received "the look".

The magnetic in the Palm Radio Paddle attaches to the side of the Eagle
when operating portable

Flagpole buddy holds the mast extending up to 35 feet

My KX3 would take up less space than the Eagle but it's a pricey little thing to leave in the camper, and I primarily use it now as my primary station in my home shack because it's wired up to the computer using HDSDR to provide a panadapter display. 

I had convinced myself that the KX3 should stay in the Shack. So being the wise and kind husband that I am; I started looking for a small, portable, inexpensive QRO capable radio, given the compromised antenna. All this was to please my wife of course.  

I used to own a Yaesu FT-857 that I kept in my truck, but it was terrible at CW (IMO) and that rig seems to be pretty rare now... After considerable searching I settled on a Yaesu FT-891.  They had good reports and I could separate the face and it would take up very little room on the table.  Plus it had a band-scope of sorts (ah shiny).  But alas, I couldn't find used ones that didn't look like they'd lived under the seat of an off-road vehicle racing in the Baja, and the new ones are out of stock everywhere.  All that web searching kept popping up the rigs with the pretty front panels.  Google decided it needed to serve me advertisements of pretty radios everytime I opened any web site.

GAS

So, I convinced myself that I needed to replace the KX3 in the shack with a shiny, teleporter control rig and permanently install the KX3 in the camper.  I could mount the KXPA100 QRP amp out of the way in the camper and leave the radio in my corner of the table.  I'd also easily be able to take it outside to the picnic table and run off battery.  My mind was made up, I needed the KX3 in the camper and a new shiny toy for the shack.

Reality Strikes

Here's the problem... my KX3 with its 10:1 auto-tuner, silent QSK relay, dual antenna ports (thanks to the KXPA100), built-in IF/IQ output, and dual key inputs (one for paddle and one for manual keys) just can't be found in a shiny, smart-phone panel radio without breaking my bank account.  So I'd have to settle for a "new rig" with fewer features than I've grown accustomed to.  Surely that would disuade me from this folly... but Google keeps serving me advertisements.

I will be soon be writing about my KX3 in the camper and my new, shiny, less-featured shack rig.

Blast you GAS ! 


The Endurance of CW in Amateur Radio

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
19 March 2021 at 11:07

CW Spans a Century

I've enjoyed using my "new" GRC-9 radio for making CW and AM contacts over the past month.  During that time I've also discovered https://worldradiohistory.com/Archive-Radio-News/ which has magazine articles about radio dating back to 1919.  Reading about amateur operators building and using equipment at the time where CW (continuous wave) was beginning to replace spark-gap operation in wireless communication made me consider just how enduring the ability to communicate using CW and AM have been. 

Prior to the introduction of continuous wave transmitters and receivers, the detector used for spark gap communication would have made it difficult to hear a CW transmission (lacking a BFO). So, even though wireless transmission and reception of International Morse Code dates back earlier than 1919; employing CW (continuous wave) to send Morse Code seems to have began its popularity around that time.  AM (amplitude modulation) phone mode was also in use at the time, and grew in popularity during the 40's and 50's until more efficient voice modes overtook it in popularity for voice communication.



Radio Telegrapher School for Enlisted Specialists 1921


What other modes have remained as popular standards using standard ham equipment and continuously in use by amateur radio operators as CW?

My GRC-9 was designed near the end of WW2 (circa 1945), and was in continuous production for various armed forces around the world until around 1974 (3 decades is a long production run).  My particular unit has a receiver manufactured by Telefunken in 1955 and a Lewyt manufactured transmitter from 1966.  I have made CW and AM QSOs with other amateur radio operators whose equipment ranged from home-brew xmtr/rcvrs, Drake and Collins radios as well as shiny new Icom 7300 and Flex radio systems.  

A modern amateur radio (typically a HF model) can be used to communicate with radios built 100 years in the past. The same might be said for AM fone (phone), but that mode has become a niche for a much smaller set of enthusiasts.

There are lots of new and exciting modes of communication in amateur radio.  Many are pushing the boundaries of weak signal reception, or alternatively allow for high transfer rates of data. But it is somehow comforting to me to consider that amateur radio hobbyists have kept one mode in particular, CW, popular and in continuous use for over 100 years using equipment that remains compatible to communicate with one another.  I wonder if that will be the case in another century?

That's all for now, so lower your power and raise your expectations

Richard, AA4OO

Modernizing the DY-88 Power Supply

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
4 March 2021 at 13:06

Go with a Modern Vibe

The DY-88 Power Supply is a marvelous design... for the 1940's.  It could take 3 different DC input voltages (6v, 12v or 24v) and output the 2 different filament voltages (1.5v, 6.3v), plus the low and high B+ voltages (105v, 585v).  It was designed to be as efficient as possible when the radio wasn't in SEND mode (receiver only) by employing a mechanical vibrator and transformer to power the low B+ 105v at about 1 amp current (when running off a 12v input).  




Turning low voltage to high voltage


Prior to the DY-88, I'd restored a 1960's Heathkit HP-13, which was a mobile DC to DC power supply.  It employed a multi-tap transformer and 2 transistors to create the needed low and high B+ voltages for Heathkit radios.  in the case of the HP-13, the two transistors worked in tandem to collapse the magnetic field in the transformer to create high voltage DC, which was rectified and filtered for the radio.




Prior to the DY-88, I'd never heard of, or encountered a mechanical vibrator used in power supplies; so it's been an interesting learning experience for me.   Vibrators were very common up until transistor revolution, for use in mobile applications where 12v needed to be transformed into much higher B+ voltages needed by hollow state equipment.

In oversimplified terms: the vibrator makes DC look like a square wave version of AC which can then be used by a transformer to raise the voltage required by the circuit, then rectified back to DC.  Low voltage DC enters the Vibrator, which contains a relay that makes and breaks contact rapidly, chopping up the DC.  It occurs so fast that the unit "vibrates" or buzzes.

The contacts eventually, become worn and pit making the vibrator less reliable.  Additionally, military vibrators (maybe others) used a rubberized insulator that broke down over time inside the vibrator, releasing a corrosive gas that would further affect the components and essentially, "stick" the contacts on the relay together, making it difficult to get started or completely non-operational.  Depending on how it the contacts "stick" the vibrator can act as a short and unpleasantness ensues.

The vibrators were intended to be disposable devices but they aren't being made anymore.  What to do?

Bad Vibrations

In the case of my DY-88, when I received it the vibrator power supply refused to start but eventually, after a bit of percussive maintenance (banging) and reapplying power it started.  Over the past couple of weeks it usually will start, but there are still occasions where power has to be switched off and on repeatedly to get it to start.  It is obviously entering failure mode.

There is a procedure using an AC light bulb in series with the contacts to attempt to freshen a stubborn one up, but the procedure is hard on the contacts and generally only restores it for a while.  It needs to be replaced, and vibrator power supplies have not been manufactured for many decades.  The NOS vibrators are generally not good due to the breakdown of the materials inside over the decades rendering them bad even if they've never been used.

The solution is to replace the mechanical operation of the vibrator power supply with a solid state equivalent.  

Solid State 

Entering the age of the Jetsons, we have these nifty things called transistors that are excellent and making and breaking contact of DC voltages rapidly and reliably.  I found a number of articles describing a solid state circuit I could build but most did not offer much in the way of circuit protection if a component upstream failed, or if the circuit itself failed.  There are a lot of difficult or un-obtainable components in that DY-88 that I'd rather not have to replace due to the failure of the Vibrator Power Supply.

I read an article by a GRC-9 enthusiast from 2004 (NC6AV) on using a commercial circuit that was designed for this very purpose to replace mechanical vibrators in vintage automobile radios https://www.radionerds.com/images/c/cd/Wire_VBN-1.pdf.  In the article describes the procedure for using a solid state replacement.

I purchased my solid state module from http://dodgem37.com/vibrator-conversion-module/ and ordered some high voltage diodes from antique radio supply to use in the conversion.  I cut apart a non-functional vibrator module to use the phenolic 7-pin base for the VBN-1 module.


Note


The instructions for soldering the VBN-1 module are great with one exception.  From the instructions: 

. . . The pins are numbered 1 to 7, pin 1 is the large diameter pin on the right, and pins are counted clockwise from that pin. . . . 

If you are looking at the base of the vibrator there are 2 large diameter pins.  The instructions say count them from the pin on the right.  That pin will be different if the large diameter pins are at the bottom rather than the top, when looking at the base.  Turn the base such that the two large diameter pins are facing you and located at the top (12 o'clock position).  Now the instructions will be correct.   This may seem minor, but when I first read the instructions I was looking at the two large diameter pins situated in the 6 o'clock position and all the pins were off-by one.

Results

The replacement circuit works a treat, except that I can't hear the faint humming from the DY-88 now when the radio is in Receive mode.  Of course that is immediately obliterated as I turn the radio to SEND and the Dynamotor leaps to noisy life.



Next step would be to JB-weld the can back to the base to restore the look, but I'm debating whether to do that.  I kinda like the look of the modern mixed with vintage vibe (vibe, get it?).


That's all for now,  keeping my heavyweight QRP GRC-9 rig on the air, one repair at a time.

Lower your power and raise your expectations, 

AA4OO

AN/GRC-9 aka "Angry Nine"

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
24 January 2021 at 14:43

 AN/GRC-9 - Long lived military comms

My lovely (and radioactive) RT/77-GRC/9

Video summary




I don't recall where I first read about the Angry Nine, but it captured my imagination.  I read everything I could find about them and decided it would be great fun to operate such an antique on the ham bands.   There is no logical reason to desire such a QRP radio.  The low power output on CW is indeed, 5 watts and high power is a pileup busting 15 watts.   The AM transmission are 1 watt and 7 watts respectively.  That's almost QRPp for AM mode.

I'd had some experience restoring old tube equipment; my Heathkit HW-101, Knightkits VFO and Hallicrafters keyer, and I figured I'd take the next plunge and learn to use a receiver-transmitter combination and see how mobile high-voltage power worked from Vibrators and Dynamotors.   

These radios seemed to have been more plentiful in the surplus market 10 - 20 years ago.  Now you'll occasionally see one come up on eBay or other sites, but often times they are in very rough shape or the they are foreign language versions.  I bid on a few auctions over the past couple of years and the bidding always exceeded my threshold for what I thought it was worth.  The one above was part of an auction from an individual who had actually trained on these units prior to deploying to Vietnam.  Later in life he became interested in finding one and spent time in military surplus warehouses going through pallets of equipment to find one in good shape.  This particular unit is made up of a Lewyt manufactured transmitter and a Telefunken receiver.  The original owner preferred the receiver characteristics of the Telefunken over the Lewyt manufactured model, so he paired the two.

Many of these old units are radioactive, due to the radium paint used on the front panels to make the lettering glow in the dark.  This particular unit is off the lower scale on the Geiger counter and must be handled with care.  Basically, I have to be careful to not touch my face with my hands after operating the unit and wash my hands thoroughly.  Radium emits Alpha particles, which are not especially strong but the resultant radioactive dust from the front panel shouldn't be breathed or ingested. I plan to paint a clear-coat over the remaining lettering to lessen the Alpha particle emissions..  

Hot receiver, in more ways than one


The AN/GRC-9 is a set of components primarily comprised of the RT-77/GRC-9 receiver-transmitter, capable of operating between 2-12 MHz in CW, MCW and AM modes.  MCW is a modulated form of CW that can be received by radios that do not have a BFO (i.e. a normal AM receiver).  

It is a mid to late 1940's design and was first documented field use in the Korean War, and was in active use through the Vietnam War and continued to be maintained in US military warehouses until 1974.  It was in use by other nations long after, most notably the Dutch military.

Out of the case, tracing a low B+ power problem

Receiver as seen from the underneath with shield removed


Transmitter with a coil for each band and that nice 2E22 final output tube




Power on the move

Designed to be used in the field, both vehicle mounted and carried by mobile infantry; there were a number of ways to supply power to the unit.  There were a few different Vibrator/Dynamotor units, that could operate from common DC voltages of the time (6v, 12v, 24v) as well as a hand cranked, field portable generator.

Keep in mind that the state of the art at the time of its design used vacuum tube technology and in the case of the RT/77-GRC/9 it required the following voltages:
  • Transmitter Plates -- 475 - 580 v @  100ma
  • Transmitter Filaments -- 6.5 - 6.6 v@ 2 amps
  • Receiver Plates -- 105 - 120 v @ 45ma
  • Receiver  Filaments -- 1.35 - 1.5 v @ 500ma
  • Keying Relay -- 6.0 - 6.9 v @ 575ma

That's a tall order for mobile and portable power supplies but designers in the 1940's were quite clever in packing power supply units.   I managed to obtain both the hand cranked GN-58 generator with the base chassis and seat for portable operations, and a DY-88 for fixed / mobile operations.  


DY-88 mobile power supply

DY-88 set to 12v powered by Amateur 12v supply

Vibrator power supply for low B+

Power filtering

I supply the DY-88 from either an RV battery or an amateur 12v power supply.  When in Standby the DY-88 draws less than 1 amp, but placing the radio in Send mode switches on the Dynamotor which draws 12 amps @12v, without key-down and up to 14 amps on high-output key-down.  It will drain an RV battery pretty quickly at that rate if the radio is left in Send mode, and works an amateur power supply pretty hard as well.  So don't expect to operate remote off a battery alone for too long if your having lengthy QSOs.  An added benefit of the DY-88 is that when the enclosed Dynamotor is running you'll have a nice extra 85 dB of generator noise to accompany your listening pleasure.


GN-58 portable field hand-cranked power supply

Generator head in carry bag

Unmounted as seen from the bottom

On the stand with cover and handles disconnected



Deployed


The GN-58 is a tough workout since it has to be cranked by hand at 60 rpm continuously.  Obviously, you need a partner unless you can figure out how to crank it with your feet while sending CW. You will also want that partner to help you carry the GN-58, and the accompanying accessory bag for the chassis and seat.  IT'S HEAVY.  I haven't weighed everything, but according to the manual that came with the set, the radio / generator / accessories including antennas comes out around 120 lbs.  

If you have a BA-48 battery hooked up then your human power supply can pause cranking while your receiving.  I have a BA-48 battery enclosure that has been gutted of the original, long-dead material and replaced with 10x 9v batteries in series for the low B+ and two D-Cell batteries in parallel for the receiver filament supply.


Accessories



Bag of goodies

The radio itself has a carry bag, as well as a bag for the GN-58 legs and seat, the vertical antenna, and miscellaneous.

There's another bag (shown above) for carrying power supply cables, keys, hand mic, long wire and doublet antennas, external speaker, torture device headphones, torture device in-ear phones, as well as a box of spare tubes for the radio.

If you're traveling in a squad sized group, then many hands make light work, otherwise you're going to be making a lot of trips hauling your QRP rig up the hill.

Headphones

These Western Electric headphones clamp tightly over your ears sealing out QRM and squeezing your head like a vice.  After 10 minutes I was confessing to sins I'd never committed. 








In order to use the headphones the RT/77 receiver must be removed from the case and an impedance switch on the back, changed from 4000 to 250 using a screwdriver.  The ham I bought my set from had constructed a CW audio filter along with an impedance switch on an outboard box, that allowed the use of the headphones without switching the impedance on the receiver unit.

Homebuilt CW filter with impedance switch

Speaker


The external speaker is a rugged, high impedance device (4k Ohms), that after all these years can still output audio at high volumes without distortion.  It has a built in thumbscrew clamp that allows it to be attached to vertical or horizontal objects.

Alternately, the thumbscrew can be used in combination with the vice-like headphones to extract information from a prisoner.

Antennas

The AN/GRC-9 comes with 3 antenna systems; a multiple section, whip vertical for quick field setup and mobile use, a long wire that can be quickly deployed in a fixed station as a sloper, and a doublet for best reception, transmission in a fixed location.



For testing purposes I have my radio hooked up to my 80m Windom, which it tunes very nicely on 80m, 60m, 40m and 10m bands. 

When the weather warms a bit I will be taking the radio out for some portable use and I'll try it out with the antennas that are part of the AN/GRC-9 set.

Spares

As a military radio, it was expected that repairs should be performed in the field when possible.  The radio shipped with spare tubes for the receiver-transmitter, as well as spare tubes and vibrators for the DY-88 power supply.


More to come

In the few days I've had the AN/GRC-9 the only problems I've encountered have been related to the old DY-88 power supply.  Old vibrators cans are generally seized up, as was the case with mine.  Eventually mine became un-stuck after repeated applications of power but there are some methods to restore truly frozen ones using AC current and light bulbs (see Notes section below).

I've made about half a dozen contacts on the ham bands, including a 40m contact to a station in TX which is kinda DX for my locale.  I've received nice signal reports.  I've specifically asked stations about my "chirp" during QSOs and they've reported it as "not bad" and "charming".  When operating from the VFO (master oscillator) rather than a crystal, the GRC-9 will "chirp". It was considered an acceptable design trade-off at the time.  I've listened to the transmitter from a remote WebSDR station to hear the chirp for myself, and I agree that it isn't extreme and lends some character to the station.  The unit does drift about 200 Hz during a QSO which I also think is quite acceptable for it's age.  It's possible that if I spent more time in Send mode prior to a QSO to allow the transmitter tubes to warm up the drift might be lessened, but keeping the radio in Send mode puts quite a load on the power supply (both the 12v supplying the DY-88 and the human cranking the GN-58).

The RT-77 Telefunken receiver doesn't offer much in terms of selectivity and on a crowded band there's a lot of stations to contend with in the passband.  The outboard CW filter deals with this nicely, but it is so narrow that when shifting from Send to Standby, the resulting frequency shift often throws the station I'm receiving out of the filter's passband, so that's a bit tricky.

The receiver's tuning knob also is very coarse, in that fine adjustments are made by breathing on the knob.  However it has zero backlash, which is amazing in a piece of equipment this old.  The markings on the receiver are in 50 kHz intervals so the only way to really figure out where you are is to look at RBN for your spot.

50 kHz spacing when reading the frequency on the receiver
Note the 7.2 is 7.200 MHz in the 40m band


Images

Enjoy the pictures of the AN/GRC-9













Phosphor glowing nicely on the GRC-9
As opposed to the degraded glow of the radium infused lettering on the RT-77 half









That's all for now

73

So go heavyweight for you QRP station to get your excercise.

DE AA4OO


Notes

Instructions for restoring a vibrator to operation

Instructions posted by:
Robert
Gunner
USN Retired
MVPA 9480

VB-1 and VB-7 are interchangable. I think I recall reading somewhere that VB-7 is a "lightweight" version of VB-1 but I won't swear to that.

The base is 4-pin, and the pin numbers are counted as on a vacuum tube with the same base. I wish I could post an image here without uploading it somewhere but if it's possible I've not figured out how to do it. The pins count clockwise from 1 to 4 looking at the bottom of the vibrator or the wiring side of the socket. The two large pins are 4 and 1 and the two small ones are 2 and 3.

There are two basic types of vibrators, called Series and Shunt. The Series type has a contact in series with the coil. VB-1, 7 and 16 are all Series types. I'll skip the Shunt type for now.

Pin 1 is common. Pin 4 is coil. Pin 2 is the NO (Normally Open) switching contact and Pin 3 is NC (Normally Closed). To test a VB-1/7, use an ohmmeter to check continuity from 1 to 4. If the reading is infinity, the coil could be open but this seldom happens. The problem is probably the vibrator contact. If the reading is a few ohms, connect +6 VDC to Pin 4 and -6 VDC to Pin 1. The vibrator should run. If it doesn't, most likely the contact is welded. About the only solution is to open up the vibrator, unstick the contact and try to burnish the burn marks out of the contact.

If the vibrator does run, go to the end of this screed and do the final test.

If the reading is infinity, here's how to use the two or three lamps to (usually) fix the vibrator. SAFETY NOTE: bear in mind you are dealing with either 120 or 220 VAC. If you jury rig the hookup, do all of your connections and disconnections with the "rig" not connected to the AC line. In other words, don't touch anything except the plug on the line cord or (if you go to that much trouble) the ON-OFF switch when the line cord is plugged in.

Connect the hot side of the AC line cord to one side of both lamps. Connect the ground side of the AC line cord to Pin 1 of the vibrator (or socket if you use one). Connect the other side of one of the lamps to Pin 4 and the other lamp to Pins 3 and 2. If you splurge and use three lamps, connect the "cold" side of the second and third lamps to Pins 2 and 3 respectively.

Check all the wiring and when satisfied all is OK, plug in the line cord. Probably nothing will happen immediately. Within a few minutes to a few hours lamp 1 should begin flickering and you should hear the vibrator hum. Run the test until the second lamp begins to flicker or until both the 2nd and 3rd lamps flicker.

If you are only using two lamps, when the 2nd lamp begins to flicker, wait 1 or 2 minutes then remove power (unplug the line cord). Connect the 2nd lamp only to Pin 2 and plug in the line cord. If the 2nd lamp flickers, remove power, move the 2nd lamp connection to Pin 3 and apply power. In either case (with the 2nd lamp now connected to pin 2 or 3 only), let the test run until the 2nd lamp again flickers.

For a final test, connect one lamp to Pin 2 and one to Pin 3. Connect 6 VDC to Pins 4 and 1. With the vibrator vibrating apply power to the two lamps. They should flicker alternately. Note that for this test, either use a 6 volt battery or a 6 VDC supply with both outputs not grounded. I wouldn't try to use the battery in the Jeep just in case you mis-identify which side of the line cord is grounded and which is hot.

Although a vibrator that is going to be fixed by this procedure will usually begin to work after say no more than half an hour, I have seen it take several hours. So if I have one that didn't start working fairly quickly, I'll let the test run up to about 8 hours max (or overnight) before giving up.

Hallicrafters HA-1 Electronic Keyer

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
16 February 2020 at 03:59

High Voltage Electronic Keyer from 1960

I've been interested in getting my hands on a Hallicrafters HA-1 since the first time I saw one online.  A 60 year old (as of this writing) all-tube keyer weighing in at 7.5 lbs.  Everyone needs one, right?




The HA-1 uses a mercury wetted relay capable of switching up to 500v circuits.  Wow!  It employs four 12AU7 tubes to perform the mark-space morse timing and uses an OA2 and OB2 tubes for power regulation.


They always auctioned for more scratch than I thought was reasonable or were so beat up that I assumed it had been buried in a damp basement since Eisenhower was president.

I finally won an auction for one that was in reasonable cosmetic condition and fully expected to have to overhaul the electrolytics and out-of-spec capacitors but I lucked out and received one that had been recently overhauled with new power caps and even had replacement polys.  The only issue was the the sidetone circuit was kaput because a neon bulb used in the relaxation oscillation circuit had broken its leads at some point (maybe during shipping) and was rattling around in the case when I received it.

Fortunately I had an old neon bulb in my junk box.  It was socketed rather than having the leads, but I soldered some leads to the socket and installed it where the other had broken off.  Wahlah, sidetone audio restored.


What an electronic keyer was like 60 years ago

After reading the manual and adjusting the circuit balance and element weighting, I had a go with it.  I found that it kept eating a DIT when it followed a DAH in a character like K or N.  I eventually realized that I was hitting and releasing the left paddle (dit paddle) before the current DAH was completing.  

A keyer without DIT / DAH memory

Then it hit me... this tube circuitry doesn't have an "memory".  Modern, digital keying circuits have a memory as to what paddle was pressed while the current element is being completed, but this old electronic keyer is using all its tube goodness to complete the timing for the current element.  So in the case of a DAH, it doesn't have a place to buffer that I've pressed and released the DIT key while it was completing the DAH.  I have to be holding the DIT paddle after it's completed the DAH for it to recognize and begin the DIT element. 

That really calls for a change in my paddle usage.  My brain needs to keep in mind the length of DAHs so that I don't rush and release a following DIT before the current element completes.  This is a bigger problem below 25wpm given the longer length of the DAHs.

The Hallicrafters HA-1 manual states that the keyer is different from other electronic keyers and requires "a knack" to use effectively.  I think I've discovered whereof it speaks.

I practiced for about 30 minutes and then tried some on-air CW QSOs.  They were rough.  Leaving DITS out of K's, C's, Q's and N's and other such letters really changes what you're saying... C's become M's... K's become M's (mmm... M&Ms)  N's become T's... Anyway, you get it.  Very frustrating for both the sender and the receiver.

As luck would have it, one of the stations I worked was also using an old Hallicrafters keyer.  Did I know because he was dropping DITs ?  No, I was telling him about the "new" keyer I was using and he responded that he was using one as well and went on to extoll it's virtues.  

So I plan to use it and not relegate it as a shelf queen.  I figure with enough practice it will actually improve my technique and probably improve my bug fist as well since it causes me to be far more conscious of my inter-element timing when forming characters.

Conclusion

If you have a good, modern keyer and don't need to key high-voltage tube gear, I can't really recommend that you run out and find a Hallicrafters HA-1.  But if your taste runs toward the eclectic and you want a really, large electronic keyer with no memory functions that consumes 30 watts of power whenever it's on and provides you with a wonderful tube smell, and also requires soldering to hook-up the line to connect to an external transmitter... then this is the key for you.

Plus it looks just like H.A.L. from the Space Odyssey 





That's all for now

73

So use a keyer with more wattage than your QRP station to get those extra DX contacts.

DE AA4OO

Space in Morse Code

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
7 February 2020 at 00:00

Silence is Beautiful

The space between characters and words is just as important as properly forming the characters.




If you're rushing your characters the elements of one character will not be easily discerned from the next and the person your sending to will find it indecipherable and respond with a 73 and spin the dial.  I have a number of comments in my logs about operators who ran their characters and words together.  I tend to avoid those contacts down the log.

But, many of us, including myself, are guilty of rushing when we send, especially as a ragchew moves into the 3rd or 4th exchange.  I think the problem is that as the person sending the code, I know what I am sending and in the excitement of wanting to get out all the things I want to say and turn it over, I start to rush and begin compressing the space between my sent characters and words.  After all, it's very clear in my head what I'm sending, it must be just as clear to the listener, right?  Wrong.

RRFBCPYALLWXHRISSUNNYES88FRIGISIC756PRORUNNING100WINTODIPOLEUP66FTDESM8ERW8BJOK

The exchange above isn't far from reality and that's assuming the character spacing was good.  When the character spacing is rushed two characters become a different character or no character at all, and you sit there with your head tilted thinking "what in the world are they saying?"

Proper Space (Timing)

What is considered proper spacing?  Let's review some basics.  A DIT is counted as a single Morse Code element (think of it as a unit of time).  A DAH is counted as 3 times longer or 3 Morse Code elements (3 times the DIT time unit).  

Of course the length (time) of a sent DIT or DAH will change with the speed you are sending.  As the word per minute speed rises, the length of of DITs and DAHs decreases accordingly and vice-versa.  Unless you're using Farnsworth timing, but that's a different discussion...

Space between DITS and DAHS in a Character

Characters other than the E and T are made up of more than a single DIT or DAH.  Between each DIT and DAH making up a single character is space.  The space between each DIT and DAH making up a single character should be as long as a single Morse Code element... a DIT.  So there's a DIT's space of silence between every DIT and DAH in a character. 

"R" = DIT.DAH.DIT (where the '.' is the length of a DIT)

Space between characters within a Word

There should be 3 Morse Code elements of silence between each letter in a word, or silence the length of a DAH, at the speed you are sending.

"WORD" = W-O-R-D (where the '-' is the length of a DAH)

Space between Words

There should be 7 Morse Code elements of silence between each word you send.

"HERE<>ARE<>SOME<>WORDS" (where the '<>' is the length of a the M character)

The length of an "M" ??  Yes.  I was corrected about this in a video I made.  In that video I was counting the DITS and DAHS only, and said to count the inter-word space to be the length of the 'W' character because it is made of a DIT and two DAHS, but I was forgetting the space between the DITS and DAHS that make up the character.  A 'W' character contains 9 elements.  An 'M' contains 7 elements since it is 2 DAHS (3*2=6) plus the inter-character element that spaces them (1-element of silence) equals 7 Morse code elements.

How to Practice

If you use an electronic keyer it will take care of the inter-character spacing between the DITS and DAHS of your sent characters.  If you use a manual key you'll have to take care of that yourself.  You can practice by sending strings of DITS, listening to see if you are placing the same space between each DIT as the length of the DIT itself.  

To practice spacing letters in a word, get used to the length of a DAH (a 'T' character).  Send a T over and over making sure you have the space of the character and the space of silence equivalent.  This gets a bit more complicated with different characters.  An 'E' character is of course much shorter than a 'Z' character but you need to have the same amount of space after each before sending the next character.  I find that I tend to rush into the next character after sending a long character like an 'F 'or an 'L' and add too much space after short characters like an 'E' or 'T'.   If you use a decoder of some type it can be helpful in showing you timing mistakes.  Send into a decoder and see if it turns two of your characters into a different character (you rushed the timing), or see if it spaces the word out as if there's a word break (you're putting too much space between the letters).  It is a very humbling experience to send into a decoder.

Similar to working on letter spacing, spacing for words is potentially an even more important skill.  When we listen to Morse at speed the rhythmic sound of the characters in a word as a whole tends to tell our brain what we've heard.  If the next word is rushed then we don't process the first and miss the beginning of the next.  Practice sending the 'M' character at your preferred speed and get used to the amount of time it takes to send.  

One thing I've tried that works pretty well is setting the break-in timing of my transceiver to match the space I want between words.  At 20wpm the DIT length is between 50-60 milliseconds depending on the measurement you use.  So if I want to be sure I'm spacing properly I should have 7 time-units or 7*50 = 350 milliseconds break-in set in the transceiver.  Both my Elecraft KX3 and Ten-Tec Eagle support setting the break-in in milliseconds.  By being sure that I hear break-in occur between every word I know that I'm putting in a good minimum amount of spacing.  If I don't hear break-in occurring, it reminds me that I'm rushing my words.

When I hear break-in occur between every word I know that I'm putting in a good minimum amount of spacing

Conclusion

The silence you send is just as important as the signal.  Silence is golden



DE AA4OO


Regulated voltage for Regenerative receiver project

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
10 April 2018 at 00:00

Mr. Regula-tor

Building a regenerative tube receiver seems to have been a rite of passage for all hams of yesteryear.  Although I built one from a kit (4-States QRP) as my first electronics project a couple years ago I thought I'd go for the real deal and build a vacuum tube regen receiver.

I'm building a design based around the 6SN7 tube. While I'm collecting parts and still locating a suitable chassis I decided to build a regulated power supply from the parts I have.  Anyone familiar with electronics could probably whip this together in no time, but being the electronics newbie that I am, it is a slow process.

I'm using a transformer from a 1950's Heathkit VTVM V-7 that I parted out. It supplies the 6.3V filament voltage from one set of windings (yellow wires)  those tested good. But the HV was an unknown as it was only half wave rectified when the transformer was used in the meter.  That meter's rectifier and power cap had gone bad so I didn't know what condition the HV side of the transformer.

Breadboarded using a full wave rectifier created with 4 diodes, buffered by a 22uF electrolytic and a 10k resistor, I saw 189 volts, with no-load out of the high voltage side of the transformer. The amount of current the transformer could provide was still an unknown. I tested temporarily with a 2.5kOhm high wattage resistor and saw 56ma of current provided with a voltage sag down to 130V but the core of the transistor started heating up.  Within half an hour it was over 120F so I discontinued that load test.

Fortunately, the regen circuit uses a ridiculously small amount of current for B+; about 4 to 5mA. Although I will likely change the audio side of the tube to deliver enough current for a speaker rather than the high impedance headphones in the current design, which may potentially double that to 10ma.  For the first incarnation I'll stick with high-impedance headphones.

The regen power supply requirements called for 6.3V@0.5A and 90V@4mA B+.  The B+ voltage  was based on using 10x 9V batteries and it stated that voltage wasn't critical but shouldn't fall much below 90V, going 12% above 90V should be OK.

Generally batteries are used with regenerative receivers because they are so sensitive to power supply noise, but I wanted to give the power supply a shot first and if it proves too noisy I can fall back to battery power for the B+ and just use the filament voltage provided by this transformer.

Since I have a OB2 voltage regulation tube I want to use. The OB2 regulates at 108V so that's what I'm going with.  An OB3 would regulate at 90V, but I don't have one of those.


OB2 in action... Glow baby, Glow!

Calculating the resistor drop

A voltage regulating tube like a OB2 ionizes gas to maintain the voltage at the tube's specification.  In the case of an OB2 it tries to maintain voltage at 108V.  It requires a starting voltage higher than what it will regulate to, but ultimately can only dissipate so much current as it drops voltage.  So, a resistor must be put in series ahead of the VR tube to limit the current it will have to dissipate.  The resistor must be able to handle the current flowing through it, so that must be calculated as well.  

The calculation for the dropping resistor resistance is:
Rdrop = (Vs - Vreg) / (Ireg + Isupply)
So, in my case:
Voltage supply (Vs) = 189V
voltage regulation (Vreg) = 108V
regulator current (Ireg) the OB2 requires 5mA to do its job = 5mA
supply current (Isupply) the actual current required by the 6SN7 up to ~ 5mA

So, (189V - 108V) / (0.005A + 0.005A)  comes out to a resistor value of  10,100 ohms.  10k is the closest standard size resistor and at 108V it should be able to dissipate 1.166 watts.  So I'll need a 10k 2-watt resistor.

Parts is parts

Running the regulated power supply with a 10k Rdrop resistor for a few hours showed the transformer stabilize at 92F degrees at 70F amb.  I was using a separate 27k 2-watt resistor to simulate the ~4mA load that the receiver will draw at 108V. 

As you can see on the newly restored, trusty Heathkit VTVM; the voltage was holding steady around 108V.  With that little current, the OB2 is not visibly glowing but with the lights out the violet colored ionization is visible.



Summary

I'm going to order a larger filter capacitor.  The only one I had to test with was 22uF 360V and I'd like to use higher capacitance value of 47uF with a more appropriate voltage rating of 250V.  I will also be adding 0.01uF caps at the input and output of the filter capacitor and I may add a 0.01uF across the OB2 pins 1/7 to further attenuate any RF noise.   

With the current values I'm seeing 50mA ripple on my regulated voltage.

A bit over 50mA ripple

After I get the new capacitor and get the 0.01uF caps in play to filter out noise, I'll hook it up to the oscilloscope to check for ripple.  I'll update the post at that time.


That's all for now....

So lower your power the old fashioned way, using a voltage regulator tube.

72/73
Richard, AA4OO

Heathkit Art

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
4 April 2018 at 02:31

Heathkit HP-23A and IM-11

I had just buttoned up a HP-23A, after testing its transformer. A fellow ham gave it to me for parts. 

This old stuff looks cool, so I took a pic with the phone and thought I'd share. 

Feel free to use as a desktop background, but if you use it in on the web or publish provide proper attribution.


Metering High Voltage on the cheap

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
1 April 2018 at 19:08

🗲 Heathkit VTM model IM-11 🗲

I recently got a taste for restoring and using vintage vacuum tube radio equipment.  Using equipment that requires 800+ volts for making QRP transmissions is counter-intuitive to the spirit of QRP ham radio, but it's part of my journey as a ham, so I'm writing about it.  Bear with me.  Once I receive a near fatal shock I'm sure I'll move back to 12v powered equipment again.

Until then...

One of the first issues I ran into while testing the power supplies I restored for my vintage gear was how to measure voltages beyond the range of my digital multi-meter.  Most consumer grade digital multi-meters (DMMs) can only measure up to 500 volts then display an error, or stop working altogether.  Previously, I was able to measure voltages over 500V by making a voltage divider out of two 100k 1w resistors and taking my measurement from the middle of the two resistors, but it was precarious in use and added even more danger when working with this old equipment.

I'd looked at getting a DMM capable of measuring high voltage, but the recommended ones, like a Tenma 72-1055 Benchtop Digital Multimeter, start around $100.  Used Fluke meters are even pricier.  I'm sure buying a more professional DMM would be a wise investment.  As I've evidenced many times; wisdom is omitted from my DNA.


So what did hams of yesteryear use?

Behold... Vacuum Tube Volt Meter


Vacuum Tube Volt Meter

This Heathkit VTVM model IM-11 was available at my local Hamfest (Rarsfest) for 5 dollars.

Debugging

Five dollars is not a princely sum, but as with most things purchased from a hamfest, it required some attention.  

The 55 year old 16uFd@150V paper, electrolytic power filter capacitor was likely a ticking time bomb so I replaced it with a modern capacitor for safety concerns.  The closest one I had was a 33uFd@160V radial electrolytic.  I don't think double the capacitance will be a problem for a filter capacitor, it will just make the transformer work a little harder when it's first turned on. I calculated the initial charge time and it's 393ms vs 190ms for the original cap. I think the 10k resistor and transformer can handle the extra 200ms heavy load on power up.

A few wires inside the meter had come loose from some very sparse solder points and a one intermittent connection in the range switch was especially troublesome to track down.
The biggest mystery to solve was oversensitive resistance readings in the Ohms mode.  I replaced the C-cell battery in the battery cup and while I had it out I glanced at the + connection for the battery in the cup.  I appeared to have oxidized at some point in the past and was discolored.  I scraped it off until I saw shiny bits and thought all was good.  I spent more time tracing the circuit and thought I had a problem with the switch itself or the 9x resistors in the range circuit, as suggested in the troubleshooting section of the manual.  The problem turned out to be that oxidized bolt head that formed the positive battery connection in the battery cup.  Scraping it had not provided electrical contact.  In fact, when I removed the bolt (after having to disassemble the circuit board from the meter for the 2nd time), I filed down the head of the bolt  and could find no conductive metal left.  I'm guessing that a former leaky battery had converted the entire head of the bolt to a very hard, yet non-conductive material.  I've never seen anything like it before and it proved to be a useful lesson.
I had to find a replacement bolt and that lead to working on my lawn mower and then mowing the yard... not sure how that progression occurred...  Eventually I got the new bolt in the cup, the circuit board re-installed.  Ohms tested accurately, put it all back together and noticed the #50 pilot lamp had stopped working (sigh).  I removed the innards from the case one more time and got the pilot bulb settled (I think it's required to balance the filament circuit).  While I had it apart for the umpteenth time, I decided to reconnect the 1/4" plug that a former owner had disconnected while keeping their original modification allowing 1 mega-ohm to be switched in for the outermost probe when DC functions are selected but switched out when AC or Ohm functions are chosen.  I wanted to allow use of an original VTVM probe used in the 1/4" plug with its built-in 1 mega-ohm resistor.

Whew!

All-in-all, I probably spent 8 hours getting all the functions on my $5.00 meter to work, replacing old parts, undoing mods and aligning it for proper DC and AC readings.  It's a good thing I don't count my time in the cost of these projects, otherwise I could have purchased a couple Fluke meters for the cost of my time.

What's the fun in buying something that works right the first time when you get it home, huh?  Are we hams, capable of solving problems, or appliance users?  Actually, it would have been nice if it worked without new parts and repairs, but I digress.

Back to the story

This meter can measure up to 1500 Volts 🗲 
The main reason I purchased this is to measure the high voltage in my tube equipment power supplies and 1500 VDC should just about cover it.

Although this meter uses a C-cell battery for measuring resistance, it runs off service mains to power the tubes which control the meter circuitry, so it must be plugged in to be used. 

I love the look of its old "Gran Tran" power transformer inside the VTVM.  They just don't make'em like they used to.



Wiring, lots of wiring

This model was made by Heathkit, from 1961 through 1968, and used typical point to point wiring of the time, making circuit tracing loads of fun.

Point to point wiring makes for interesting circuit tracing 

Shiver me timbers, it's got decks


Fun fact:  When reading the schematic it will refer to "decks".  A "deck" is a wafer section.  When there are stacked sections as there are in the function and range controls the "front deck" is the one closest to the knob (front of the case) and the "rear deck" is the one furthest away, or in the case of working on it, the one closest to you.  When there are more than two decks, as is the case with the range control, it will refer to the "second deck".  As you'll likely guess by now, that is the second "deck" or wafer disc from the front of the instrument.

It also refers to "front half" and "rear half".  The "half" is referring to a side of the deck, so in the case of "front half" it refers to the side of a particular deck facing the front of the instrument, while the "rear half" is the side of a deck facing back (or toward you).

Clever voltage divider circuitry, what could possibly go wrong in this triple stack of wafer switches?



The left knob controls on/off and meter functions while the right knob controls the rather elegant voltage divider.

A knob for every function and a function for every knob.  NOTE: do not plug your headphones into the 1/4" jack on the front unless you want to experiment with personal electro-shock therapy.  Better, yet, don't plug your headphones in there.

Not clearly shown in this photo, voltage divisions up to 1500 volts supported

"...Weighed in the scales and found wanting"


Ok, how many of you understand that completely unrelated biblical reference?

I haven't used a meter like this since I used to plan my VFR flights using an E6B.  My modern, digital multi-meter is fairly idiot proof in terms of reading the results.  My DMM auto-ranges and displays the correct unit of measure along with the reading on its display.  It works well for a dummy like me.

A VTVM on the other hand, has a number of scales that must be interpreted based on whether you are reading DC, AC or Ohms.  Additionally, you have to pay attention to the range chosen.

Choose a reading... any reading, just use the correct scale
Note: the needle isn't at zero in this photo because I had just plugged it in before taking the picture and the tubes hadn't warmed up.  Ah, the joys of vacuum tube powered equipment

The voltage markings for the range switch refer to the full scale reading.  Resistance is the top scale, but let's ignore that because we're talking about measuring voltage...  The second scale from the top is Voltage.  Even though it appears to refer to DC for the numbers on the top and AC for the numbers on the bottom of that second scale that's not what's going on.  The second scale is for both DC and AC.  The numbers on the top are when you are using a range that is a multiple of 15, such as 0-1.5V 0-15V 0-150V 0-1500V.  The numbers on the bottom of that scale are for the ranges using a multiple of 5, such as 0-5V 0-50V 0-500V.   Clever eh?

You have to do a bit of math.  For example, if you if you're using the 1.5V range take your reading and move the decimal place one to the left.  So, a reading of 8 would represent 0.8V in the 1.5V range, while it would actually represent 8V in the 0-15V range and 80V in the 0-150V range, etc.  See, hams were smarter in the 1960s.

Always start with a range larger than what you expect the voltage to be and reduce the range for a more accurate reading if it occurs in the lower 3rd of the range.  The voltage divider set by the range knob is protecting the circuits so if you have it in too low a range and apply high voltage, bad things will likely occur.

Old school needle gauge.  There's a lot going on behind that needle.  It operates very smoothly.



Sporting some temporary probe hookups

Making probes

This meter did not come with probes. I bought another older VTVM pretty cheap, for parts from a famous auction site because it was advertised as having a full compliment of probes, but alas, they were not usable. Even the 1/4" plug from those probes was a bust. However they did come with rebuildable probe "ends"  
I used a RG-58 cable as the high voltage DC wire using only the center conductor and grounding the shield even though it is not used as the ground return. I also placed a 1/4 watt 1 mega-ohm resistor at the tip of the probe to limit any current through the probe cable.  That cable terminates in the 1/4" plug and is wired such that it is out of the circuit in the Ohms position. I secured the cable into the probe body with some glue and used two layers of shrink wrap as a strain relief.  I also put some shrink wrap near the probe tip as a bit of extra insurance.

 I used a spare DMM cable for the outer positive banana plug feed used by the AC and OHMS circuit and made a heavily insulated cable with an alligator clip for the ground probe that goes to the other banana plug. 

The outer probes are used for measuring resistance, AC and low volage DC. The center probe is used only for high voltage DC positive. Both positive probes would not be connected at the same time (as they are in the image below), and would present a shock risk if they were both connected when measuring voltage.



Summary

If you need a way to measure high voltage or are looking for a really eccentric meter to make common measurements harder than they should be get one of these VTVMs.  They seem to be commonly available at hamfests and on famous auction sites for under $10.

Dazzle your friends next time they ask you to measure something for them, by whipping this not-so-little-puppy out of your back pocket and powering it up.  As you're making your measurements quietly repeat "Mmmm, yes.  Mmmm yes, I see now".    They'll have no idea what you're referring to and be quite impressed.


That's all for now...

So lower your power and measure it with the low-range on your snazzy Vacuum Tube Volt Meter

72/73
Richard AA4OO

Remote VFO - Knight V-44

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
15 March 2018 at 11:29

Everyone needs a remote VFO from 1955

Late night eBay surfing, and poor judgement led me to bid on a Knight V-44... and unfortunately won it...

Note to self: Never browse eBay just before you go to sleep

The 1955 remote VFO was unique because it had a built-in power supply.  It's also interesting that its base oscillation frequency is in the 160m band.  Using harmonics from the base frequency means it doubles for each subsequent band (x2 for 80m, x4 for 40m, etc.)  That doubling means it also multiplies the drift.  Specified drift is 300Hz an hour.  That doesn't sound too bad, but multiply that by x6 up in the 10m band and holy-smokes, it's drifting 1800Hz an hour.

That's gonna make operating CW like a game of chase, or hide and seek after every exchange.

This is gonna be fun.


Surprisingly the big dial is actually operating the variable cap through a reduction gear and it's very smooth

Uses 4 tubes. Power supply up top, VFO circuits in the bottom to minimize impact of heat from the PS. 

Power supply

old electrolytic power filter cap  must be replaced

10k 7watt resistor had failed

Replacement bits

The 450v electrolytic cap must be replaced for safety reasons. All the other components measured within 10% of specifications except for the 10k 7w resistor connected to the OA2 tube. It had gone up into mega ohms of resistance, which is likely when the VFO was taken out of use.

Handwritten notes inside the chassis indicated the VFO tubes had been replaced in 1977. Until I get the replacement parts for the power supply I won't know the condition of the tubes.

Plans


I plan on using this with a Homebrew transmitter that I may build sometime this summer.

Surprisingly, it outputs 10 volts of signal, so I may also build an output filter and use it as a QRPp transmitter on its own.


The possibilities are endless.

Update 3/21

Repaired

The replacement parts arrived from Mouser...  A 500v 47uF electrolytic capacitor and a 10k Ohm 7-watt resistor.  The new high wattage resistor is tiny compared to the giant, defunct resistor that was in there before, and of course the capacitor was about 1/3rd the size of the original.  I used some spaghetti on the capacitor leads since the lead lengths were so much longer with the replacement cap.  So the power supply section was now repaired.

I also replaced the 2-blade, non-polarized, ungrounded, un-fused 1950's power cord with a 3-pin grounded plug and added a 1-amp/250v inline, replaceable fuse.  So hopefully there's a reduced risk of death or fire now.  Electrical safety didn't seem to be foremost on the minds of kit builders 60 years ago. The size of the 3 wire power cable and it's much thicker insulation didn't fit the opening in the back of the VFO as both the power cable and the VFO output come through the same hole, so I had to remove the insulation and use heat shrink to get things to fit.  Additionally the large in-line fuse holder didn't fit well inside the VFO housing so the wiring is quite a bit more cramped in there than it was before.

After the components were replaced and the wiring was complete I plugged it in... no-smoke.  Then I flipped the repaired switch (the phenolic disc for the on-off switch was broken in half when I received it), and wallah! The indicator light lit up through its pretty little blue jewel eye.  So I knew the transformer was supplying 6.3v for filament.  I heard a low hum from the little transformer and then the tubes began to glow.  The OA2 was glowing it's pretty violet color, and no bad smells were emanating.  I was ready to button it up and begin calibration.

The sparse instructions directed me to back out the tuning slug for the 80m band nearly to the end and screw in the slug for the other bands all the way, so I did so.  I set the trimmer caps C1 and C2 to their fully engaged positions.

I carefully re-installed the front face holding the VFO and PS sections it in its heavy-duty case, taking care to get all the new power cord/fuse wiring inside the VFO section from binding up on the sharp edges of the case as it went in.  In screwed in the plentiful 10 screws that holds it together and Bob's your uncle.  Well, maybe Bob isn't your uncle but I just wanted to say that.

I had already attached an RG-58 coax to the output inside the VFO and run it out the hole with the new power cord, so I then installed a BNC connector on the end of the RG-58 to make hookup easy.  I like BNC connectors because they are secure and I have lots of adapters for different connectors.  I then connected the VFO output to my Elecraft CP1 RF coupler and terminated the other end with my ugly dummy load.  I connected the RF coupled cable to the Oscilloscope and turned everything back on.

Calibration

I let it warm up 20 minutes or so.  The cabinet does not get very warm, just about 15 degrees above room temperature.  That's actually a good thing, from what I've read.  If the VFO is at room temperature then it's more susceptible to the variations of that room temperature.  Having the case stabilize above room temp can make the VFO more stable.

I had my frequency counter attached to an output from the oscilloscope.  In the 80m band setting with the VFO dial set to 3.5 Mhz the freq-counter was reading around 1.75'ish.  The VFO primary oscillation roams around the 160m band and generates the first harmonic in the 80m band.  The freq counter had trouble tracking due to all the harmonics, and the output on the oscilloscope was not very pretty because it was showing the primary frequency with the first harmonic interfering.

I was unable to properly calibrate the VFO using a frequency counter, due to the interference from the harmonics, so I turned on my SDRPlay, software defined radio.  It can display up to 10 mHz bandwidth but for this test I was displaying 2 mHz bandwidth so that I could easily see the harmonic for the band I was calibrating.

That made quick work of calibration.  I adjusted the variable capacitor C1 (near the bottom left hand side of the VFO) for the 80m band and adjusted the one above it for the remainder of the bands.  I was able to verify that adjusting the VFO dial in the CW portions of the bands was extremely accurate with regard to frequency.

It appears to work like a charm.  I hooked up a key and even sent some test messages and listened to them on the SDR.  I'd been advised to not key the VFO directly because it tended to chirp but frequency stability was much better than I expected.  Over the course of an hour that I was calibrating I saw very little drift after the initial warm-up.

Here's a little video demonstrating the completed calibration...





That's all for now .

So, warm up your Tubes and spray some RF into the air.

73
Richard ,AA4OO

Need a Vacuum Tube?

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
10 March 2018 at 01:07

Superstore for Vacuum Tubes

When I started restoring my Heathkit HW-101 I thought it might be difficult to find replacement tubes.  I initially only looked on eBay for tubes but then I was directed in a boat anchor forum to the vacuum tube superstore... findatube.com

Bob Dubush offers tubes at prices well below what you'll find on eBay.  When you order from findatube you'll receive NOS (new open stock) tubes in their original boxes and may receive them in a nifty original store display box...  Ah I can smell the 1950's




 He also carries hard to find tubes like the 6GW8 at far better prices than what you'll find on the 'Bay.

So if you've been looking for a good source for all your classic vacuum tube needs visit...





That's all for now...

So fire up that high voltage power supply and warm your shack the old fashioned way

73
Richard AA4OO

Oscilloscope now on the bench

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
9 March 2018 at 01:16

Tektronix 475 Oscilloscope and Android Signal Generator App

When I was debugging problems with my Ten-Tec Century/21, and especially my problematic one-watter kit, I needed to see more than DC voltages.  I carried my problem stuff to my friend Paul to see what his scope and signal generator revealed. 

Why would a ham need a scope?  Audio and RF are both AC (alternating current) and a voltmeter alone doesn't offer much insight into that world of voltage across time and phase.

I almost bought an inexpensive digital scope last year, then thought better of it.  Then I almost bought a featured digital scope and checked my wallet and thought better of it. A good digital scope in the 100 Mhz and up range from reliable sources costs upwards of $500.  On the other hand, older professional scopes that have been well maintained and kept in calibration are excellent choices and will last a lifetime.  You do give up handy on screen cursors for measurements, so you have to count divisions by hand and do the math.  You also don't have digital storage in a digital scope, but smart phone cameras and video can make up for that.  

When I saw this recently calibrated Tektronix 475 listed in the classifieds on eHam.net for a nice price, I decided it was time to step into the world of visualized AC.

Watching a capacitor charge 250 times a second
The lines are a bit wide because the signal source was noisy

Tek 475 Specs

The Tektronix 475 is a portable (30 lbs), dual-trace oscilloscope with dual time-bases similar to the 465, but with 200 MHz bandwidth and a maximum vertical sensitivity of 2 mV/Div. It is all solid-state except for the CRT. It was introduced in November 1972.  

This scope cost $3,000 when it was new.  Now you can find them in good condition for less than $200.

  • Bandwidth --  200 MHz (475), AC cutoff 10 Hz, switchable BW limit 20 MHz
  • Rise time -- 1.75 ns (475)
  • Deflection -- 2 mV/Div to 5 V/Div, 1-2-5
  • Cascaded mode -- 400 μV/Div, 50 MHz with CH1 input connected to CH2 VERT SIG OUT
  • Time base -- 10 ns/Div to 500 ms/Div, 1-2-5, and ×10 magnifier
  • Input impedance -- 1 MΩ // 20 pF
  • Triggering -- 0.3 Div (int) or 50 mV (ext) to 40 MHz, increasing to 1.5 Div/250 mV at 200 MHz; AC coupling >60 Hz; LF REJ >50 kHz, HF REJ <50 khz="" li=""> 50>
  • X bandwidth -- 3 MHz
  • Z axis input -- 5 Vp-p, 50 MHz
  • Calibrator -- 1 kHz, 30 mA / 300 mV square wave
  • Outputs -- CH2 Vert Signal Out, 20 mV/Div into 1 MΩ or 10 mV/Div into 50 Ω; A and B +GATE OUT, +5 V; Probe power jack
  • CRT -- 8 × 10 cm², P31 phosphor (P11 opt.)
  • Power -- 110, 115, 120, 220, 230 or 240 VAC ±10%, 48-440 Hz, max. 100 W

Real knobs and switches

One advantage of an analog scope is that there is a labeled switch or knob for every function. No need to dig through menus to figure out how to do something.  To me this is the a true advantage to finding a well calibrated, analog scope.



An oscilloscope needs a function generator

An scope let's you visualize AC within a circuit, but when you testing  something you often need to inject AC into that circuit.  That's the role played by a function generator.  Function generators allow you to choose a frequency and a wave type (sine, triangle, square, etc.), or sweep across frequencies.

In general, the higher the frequency they support the more they cost.

If you have a mobile device you can get one that uses your headphone jack as output up to 22 kHz for free...



For a free app it is very nice.  It outputs sine waves very well, triangle waves are a bit soft pointed and square waves are for entertainment purposes only.  But it is free so I won't complain.  In the image below you can see the oscillations as it tries to generate a square wave but the audio amplifier of the mobile device just doesn't have that kind of control.

Frequency Generator App set to 1 kHz

Square Wave?

Square waves are not

Reduce the time base to zoom in

Yea, square wave.... not so much

The square wave is bad but sine and triangle waves look good until the frequency get's near the top of the range or the amplitude is raised too high.

Sine Waves look good

Triangle waves are on as well until you go up in frequency


The free app is inadequate for bench testing

While I appreciate that this would be a useful, portable signal generator for testing audio circuits, I'll be ordering a purpose-built function generator because generating clean square waves is an important test signal to be clean.  I also will need a generator that works above audio frequencies, hopefully up the the IF frequencies of the some of the equipment I'm testing.

Only the beginning

Having an oscilloscope is a new adventure for me.  I have another 1-watter kit ready to build that I've been holding off on because I wanted a scope for troubleshooting.  In the meantime I'm using the scope to watch transistors trigger and measure the timing circuits I'm building and learning how to control the scope.  The Tektronix 475 is a feature-rich analog scope.  If you plan to fix your own equipment or do some homebrew electronics work a scope can come in handy.


That's all for now

Sow lower your power and sample it with a scope

72/73
Richard AA4OO

Feeling gassy

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
28 February 2018 at 23:51

Ionization is a beautiful thing


A reader asked me to video the pulsing of the OA2 voltage regulator tube in action. 

OA2 VR tube glowing beautifully in back corner



I turned the room lights down to capture the OA2 in its glowing gas glory and noticed a problem with the V15 6EA8 tube that creates the sidetone oscillation and Vox control. A patch inside was glowing a brilliant violet color when the CW switch was engaged. Glowing gas inside a gas filled tube is pretty but glowing gas inside a vacuum tube is a no-no.  I've noticed my sidetone volume (which is unadjustable) going a bit soft over the past week and now I understand why. The vacuum tube has developed a leak and has "air" inside.  That "air" is mostly nitrogen which ionizes with this brilliant violet color. 

Tbis 6EA8 should not be glowing violet

Lots of flatulent tubes


After I saw that I started looking and noticed I also have an 12AX7 beginning to go gassy as well so I ordered some new tubes from www.findatube.com

So let's keep the gases where they belong.

Solved a bit of a mystery tonight

I had a problem that I've just tracked down. Most boat anchor guys would probably already have known how to solve this but it a new discovery for me.

My audio was occasionally scratchy with a bit of popping.  Sometimes when working CW the other stations signal would jump around slightly in frequency, like 20Hz - 50Hz. 
I'd already re-seated most of the tubes, re-tightened screws, DeOxit'd switches, etc.  

Then I noticed that V1's tube shield was not bonded to the tube socket finger thingy (sorry don't know what it's called).  The other tube shields were soldered and I hadn't noticed that this tube shield was new and looking at the socket spring thing appears it had never been soldered.  After pulling that tube and its shield I scraped the paint from the shield where the socket spring presses onto it and cleaned the socket spring as well.  Apparently those tubes leak RF and the tube shields catch the stray signals and send them to ground.  Without proper bonding the tube is spraying RF around.

That turned out the be the problem, now all is good. Received signals are rock steady and the audio is very clean.  

Tube shield needed to be grounded to the socket spring


This problem had been periodic and was driving me a little nuts.  I'd read that grounding the tube shields was important but somehow I'd missed that this shield was not properly bonded to the finger thingy.

On the positive side, I am growing a tube collection by purchasing replacements that are not needed :)


That's all for now

So lower your atmospheric pressure and raise your B+ voltage

Richard AA4OO

Voltage regulation, tube style

✇Ham Radio - QRP
By: noreply@blogger.com (AA4OO)
24 February 2018 at 19:57

High voltage indeed

The Meter on my Heathkit HW 101 stopped displaying ALC (dropped down to the negative stop).  So, I opened up the old rig to have a look. I found that the B+ voltage was reading 33 volts higher at one of the test points than it should. Ultimately that voltage didn't turn out to be the problem with the alc meter instead the meter switch had become dirty and needed to be cleaned. But in the process it got me to studying the way voltage is regulated in the Heathkit and I learned a bit about voltage regulation tubes like the OA2 used by Heathkit.

OA2 tube
OA2 in action at the right rear of the Audio board, notice the glowing gas inside

More Glow...

Look at the pretty violet glowing gas in the OA2

The OA 2 is actually not a vacuum tube it contains a gas that ionizes and in the process of ionization acts as a voltage regulator.  In a vacuum tube, if you see glowing gas inside the tube that means it's leaking and has become "gassy", that's a bad thing.  In the case of a gas filled tube like an OA2 you expect to see glowing gas and if you do not, then there's a problem.

In this case The OA2 regulates voltage to 150 volts and current is limited by the two high-wattage resistors connected in circuit to that tube (seen beside the OA2 in the photo above). Those resistors are dissipating a lot of heat.  I measured over 300F degrees with my IR temperature gauge (ouch).

Tube Testing without a tube tester?


I emailed one of the members of my local club, Joe WA4GIR to ask about tube testing and he sent me the following,  which he gave me permission to post:

The lack of a tube tester is not a limitation.  You can tell a lot about a tube test by looking at the voltages in the circuit.  If the filament goes out, the tube is dark and does not conduct.  That one is pretty obvious.  If the tube cathode loses it's ability to emit electrons, the voltages dropped across the cathode resistor and any resistors in the plate or screen grid circuits will change (the voltage drops across those resistances will drop).  A good tube tester will measure the ability of the tube to vary the plate current for changes in grid voltage, and you can see this with a scope by looking at the AC voltages on those elements, at least for the audio circuitry.  Probably not so much for the RF circuits as you are affecting the circuit when you probe it.  The best way to check for a suspect tube is to replace it with another.  I have 0A2's new in the box.  I may have the other tubes pulled from radios but it takes longer to look through those as sometimes the numbers are hard to read.  Hint. to bring out a faded number, rub it on the hair on the back of your neck-- better if it's oily.

A lot of resistors in old tube-type radios were 20% tolerance so don't expect the voltages to be that precise.  Tube rigs had much more variability than modern solid state circuits.  For the unregulated voltages, the precise voltage will depend component tolerances, tube health, and line voltage.  The line voltage here is about 125 when where I lived in Raleigh it was around 110.  You can do the percentages but that alone will account for some of the variation you might see.  I don't think that any of your tubes were damaged by overvoltage.  If they are drawing too much current, they will get hot, and in severe cases, the plates will glow red.  That's a concern.  Much less than that, the life might be reduced but I don't think you will see any short term effect.  When I've run tubes too hot, you might see signs of the tube going gassy, which is indicated by a blue low in the space inside the tube that is supposed to be a vacuum.

If you want to see the plates of a tube glow red, operate the final mistuned so it is drawing too much current.  They will glow red, haha.

The voltages out of the 0A2 are different -- they should be held pretty closely to 150V. I don't know the exact tolerance.  It might be a few percent.  So in your radio, 150V supply and any that are derived from it are the only ones that would have a  tighter tolerance.  The 0A2 has an operating current range of 5 to 30ma, and an operating voltage of 150V.  The supply voltage should be at least 185V to get the tube to "fire" but once "on", the voltage feeding will drop to the 150V level and be regulated there by the action of the tube which causes the voltage drop across to change (like zener diode regulators).  The regulation comes from the fact that a very small increase in the voltage across the tube results in a significant increase in the current so the resistor values are chosen so that the current through the tube remain in the 5 to 30ma range as the input voltage and the current draw of the regulated circuits varies for whatever reason.  Remember the current draw when you first turn on the rig will be low because the tubes don't conduct until the cathode gets heated so the designer must account for that in the selection of the input resistors to that circuit.

More to learn about hollow state


As a young-ish ham I certainly have a lot to learn about old tube radios but I'm enjoying the journey. Just the thought of transistors operating by thermionic emission, tossing their electrons across empty space, being attracted to a plate with more positive voltage is fascinating to contemplate.


That's all for now

So lower your power... or at least regulate it with a OA2... and raise your expectations

73
Richard, AA4OO

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