Normal view
Bah humbug - NOT amateur radio
Adding an external keypad to the K3
Logs 5 Oct 2024
1620 1835 Radio King Kong. SINPO 54444.
1627 1842 Radio Turftrekker. SINPO 54444.
1636 1830 Radio Mi Amigo. SINPO 34433.
1655 1927 Radio Manolito. SINPO 34433.
1665 1918 Radio Twentana. SINPO 44433.
5030 1908 Deltracks. SINPO 44433.
5055 1855 Radio Activity. SINPO 24432.
5840 1648 Polka Radio. SINPO 24432.
5843 1850 Radio Joey. SINPO 54444.
5880 1715 Radio Rock Revolution. SINPO 54444.
6210 1655 Radio King Shortwave. SINPO 44433.
6290 1700 Radio Akenzo. SINPO 54444.
6300 1635 Kiss AM. SINPO 54444.
6380 1642 Radio Pandora. SINPO 44433. Heard on 6375 at 1725 (54444).
6935 1708 Coast FM Classic Gold via relay. SINPO 54444.
QSL Cards - Letβs Fix This
Having convinced myself that QSL cards are indeed an important detail in our daily amateur radio lives, the question becomes how can this practice be saved and restored? Assuming the cost of a printed QSL card purchased in bulk is around 30 cents each, and an optional envelope 20 cents, weβre looking at roughly 50 cents before postage. First-class postage these days costs 73 cents though post card stamps are 56 cents so there are a few options for savings.
But these numbers arenβt static. The rise in postal rates has been steady and frequent and thereβs no reason to believe that might slow down. The current worst case situation for QSLs is sending a card, in an envelope, with an SASE inside. That comes to $2.16 per QSL at todayβs rate. Send 500 of those a year and youβre out more than a thousand dollars, an expensive proposition for any of us.
Thatβs the main reason why βfreeβ Logbook of the World confirmations seemed like such a good deal. And it is, if your interest is only collecting ARRL awards. But LoTW provides only a check mark on a big spreadsheet intended for ARRL awards. Thereβs no place for photos, personal notes, equipment, antenna or how much power was used, etc. And as we have seen this last summer, LoTW comes with the possibility of problems. We know now the original system, which is still in use today, was assembled with baling wire and duct tape twenty years ago and there is apparently nothing to replace it on the immediate horizon. Itβs free, for now, but rumblings and rumors persist that ARRL will one day assign a fee to use it.
We need a completely new service, and itβs probably best if itβs not from ARRL, that permits storage and retrieval of QSL card images. These could be from a static image that could be edited to add pertinent QSO data along with comments, etc. Someone would log into the system, see that they have waiting QSLs that hadnβt been viewed, and have the option of downloading those images or simply viewing them online. It would be nearly the same as traditional QSLing, but without the postal burden - or the actual paper card.
Of course the ARRL (and others) wonβt accept these confirmations for award credit, but who cares if you arenβt interested in ARRL credit? And if you are, you can continue to use LoTW too. No harm, no foul. A system like this would provide an option to inexpensively send a reasonable facsimile of an actual QSL card complete with photo, comments, and everything that makes a QSL card special.
While there are services now that allow these to be sent via email, I think it best that whatever comes next be a service where retrieval is optional and doesnβt come via unsolicited email. I simply want to log-in on occasion, and download whatever is available for me. Iβd be willing to pay $20-$30 a year for such a service so I think there is a potential business opportunity here for someone, doesnβt matter where, to jump on and build something fresh and new.
Letβs fix this and resume the quaint, cozy practice of collecting QSL cards.
- Q R P e r
- Helene Aftermath Update: Egress, FEMA, Resource Organization, and the National Guard (Saturday October 5, 2024)
Helene Aftermath Update: Egress, FEMA, Resource Organization, and the National Guard (Saturday October 5, 2024)
Amateur Radio Weekly β Issue 350
Carn aβGheoidh
After a lovely day yesterday on Lochnagar and Conachcraig, I was looking to see where I could go today. There was a swimming competition on, in addition to the usual activities, so I needed to be back for 3pm. Last week when I was on An Socach, the others went to Carn aβGheoidh, and I remembered them leaving later than me but arriving at the top at the same time. Sure enough when I check all the times, it looked doable to get there and back in time. The longest part is the drive to Glenshee ski centre, and thatβs right at the limit of the electric car - returning home with 20 miles range still makes me a little nervous!
The weather forecast had it cloudy with chance of showers and reasonably breezy. It did rain a little on the way out but was dry when I arrived. I wasted about 10 minutes getting a parking ticket from the cafe - I shouldβve just opened the link in the car park when I was up the hill and had signal, like I did with Glas Maol.
The track follows up the ski maintenance tracks, which are quite steep to start. Thereβs a shortcut across part way up which I just walked right past. My Inreach mini started beeping as Iβd gone of course and so I backtracked and found it. It was a small track at right angles to the main path just behind a fence, so not too obvious, so thanks to the Garmin!
I was soon in the cloud and did check on the inreach every so often to make sure I was heading in the right direction. I doesnβt have topo maps, and just a line but it has a compass and so points in the right direction and is enough to make sure youβre following the right path.
I didnβt see much on the way up, other than about 20m around me, mostly looking like the photo. In exposed places the wind picked up a lot and gave me a good push. At one point I was about 3m from a small loch and I didnβt realise until I was right upon it. The track was decent and only in a few places was it boggy but nothing like The Buck. The final ascent to the summit is steep again after a while of walking on the mostly flat plateau. At this point the wind was howling and I was glad there was a cairn at the top.
I setup behind the cairn, which was a very good shelter from the wind, had a sandwich and then got on the air. I thought Iβd try a bit more power on 2m and see if I could get any further than usual. Iβd brought the Kenwood V71 and battery. This is the first time Iβve taken it out with me, and I also havenβt used it much at home, so I was hoping I wouldnβt get into any operating issues with it! I had the slim G, and was glad I hadnβt brought the yagi to try and setup in the wind.
I now wonder if Iβd setup the mast on the outside of the cairn pointing into the wind, if I couldβve made it more vertical. Particularly as right at the end the antenna got blown off and I ended up holding it with my arm to finish the QSO - I didnβt do an EMF assessment on that setupβ¦
It was a little slow to start, but eventually Iβd work 9 stations, including GM4OAS 90 miles to the west in Mallaig. I did find the lowest squelch on the V71 was quite high and not breaking for several stations. I eventually turned it off and then heard several locals and others. I do wonder how many had been replying to my CQs before. Did 50W make any difference? The map looks remarkably similar to when I was on Glas Maol, and that was with the 5W D72 handheld. Technically, itβs 10 dB which is 1.x S points, and on Glas Maol GM4OAS gave me 32 and this time he gave me 42, so whilst not more power, I was readable more? I do like the form factor of using the mobile rig with the fist mic, means I can position things easier than being tied directly to the end of the mast, but probably for the most part it makes no real difference and itβs all in my head!
Keeping an eye on the time, I needed to pack up and head back. The wind was still relentless and on the top I had to lean into it. I was grateful of my big hood as I followed the path back down. Itβs amazing how you can forget some of the details of the walk on the way back, being surprised that I had to climb up and down a few places which I didnβt remember on the way up to the summit! For a few moments the wind seemed to blow the clouds away and there was even a hint of sunshine coming through. The view opened up and I could see all around. Certainly not the spectacular views of last week, but enjoyable for the few moments. Back down to the car and back home.
I think this summit and Glas Maol would make a nice day trip out, one in the morning and one in the afternoon, with the option of a hot lunch at the ski centre cafe. For 6 and 8 pointers, they have fairly easy and short walks, and both great locations for 2m, particularly to the south. Doing both would be 14 points, and a lot less walking and climbing than my 14 point day yesterday on Lochnagar and Conachcraig!
8m: Oct 5 - DXing (S51ZO, S51DI, ...)
Rallies this weekend
Β The following have been notified to me. Always check before going far.
- Sat Oct 5th - Carmarthen ARS Surplus Equipment Sale, Cwmduad, SA33 6XN. Contact G0JLX @gmail.com (shown as ....@mail.com which I think is an error?).
- Sun Oct 6th - Welsh Radio Rally, Newport, NP18 2YE. Contact welshradiorally@gmail.com.Β
10m 500mW WSPR (Saturday)
8m QRP FT8 (Saturday)
Β My 2.5W to the horizontal low dipole was turned on at about 0812z. The usual "watering hole"Β for both FT8 and WSPR is 40.680 MHz USB dial. If you set your receiver here you will catch most of the activity.
UPDATEΒ 0951z: G0KTN (211km) has at last spotted me. Pretty sure he has been trying for some time. Not sure if he has a better antenna, higher antenna, more sensitive RX or if conditions were up. Also spotting me was EI3KF (574km).
UPDATE 1000z:Β It would appear that every time I try 8m QRP FT8, I get spotted by several stations. If I get spotted with my very tiny power (2.5W) and low dipole then imagine the results with 50W and a beam. ThereΒ have been some amazing 10mW FT8 QSOs. Under ISM rules many countries can TX on the bandΒ Β without a special permit or even a licence. Check what the rules are in your country.
Stations spotting my 8m FT8 today |
Sunspots - Saturday October 5th
Β Solar flux is 291 and the SSN 180. A=8 and K=1.
via Hackaday: Blowing Up Shell Scripts
Conachcraig
After the big hill, it was time to do the small one - Conachcraig. It certainly looked small from Lochnagar summit but itβs still a respectable 865m tall.
It felt like a short, straight up route on a nice track. I turned and looked back at Lochnagar and could see the cloud hovering over the summit, although not submerging it.
The rock formations on Conachcraig are interesting to look at, I havenβt really got a good photo of them so youβll have to go there yourself. Unsurprisingly, no-one else was at this summit with me and I ducked down behind a rock to keep out the wind whilst I setup again on 2m.
Thanks again to Fraser, MM0EFI, and Chris, 2M0RVZ for their contacts on both summits, then with Simon, GM4JXP, and finally Richie, GM1LKD, in Aberdeen I was set. It was now 3:05pm, and I needed to be home by 5pm, and with an hour+ drive, it was time to pack up and head back to my bike.
The downhill bike ride back only took 20 minutes, and was a great way to end the trip. 28 km all in, and home in time!
Transformers and magnetic saturation
It seems that even a basic but sound understanding of transformers challenges lots of hams, and even online experts that have been heard to brag of their qualifications so as to intimidate others who might question their words.
So at ARRL EFHW (hfkits.com) antenna kit transformer β revised design #1 β part 2 I estimated that at a current of 4Arms marked the onset of non-linear B-H response, ie the onset of saturation.
One online expert proposed a method that would rate this transformer at maximum 4^2*50=800W at which magnetic saturation would occur.
The referenced article estimated saturation at more like 17000W.
Some very basic transformer concepts
Letβs talk about some really basic transformer concepts.
The diagram above from Wikepedia shows a rectangular magnetic core with two windings, a primary and secondary on opposite limbs of the core.
Note the phase polarity markings (+ / -) and the direction of (conventional) alternating current.
An example for discussion
Above is an example power transformer for discussion,Β 240V 50Hz 100VA, n=Vs/Vp=1/20, rated primary current 0.416A, core mass around 800g, estimated core loss at 1W/kg is 0.8W, for a simple explanation, leakage is assumed zero and rated load is assumed purely resistive. Note that an AC power transformer is typically rated for primary voltage, frequency and VA, and that they are operated into the low end of BH saturation, a compromise between weight, dissipation and efficiency (and cost of course).
Letβs assume that it is a good design, and for a first analysis, letβs ignore flux leakage, ie flux due to current in one winding that does not induce voltage in the other winding (does not βcutβ the other winding). Letβs analyse it with no load and rated load.
No load
With load load, assume zero current flows in the secondary.
The primary winding acts like an iron cored inductor, when voltage is applied, current flows. The current produces magnetic flux and a voltage induced in the primary winding which by Lenzβs law opposes the voltage that created the current.
The current that flows with no-load is known as the magnetising current, it establishes magnetic flux in the core.Β In a good design, the magnetising current is small wrt rated current. We can extend that and talk of the corresponding magnetising impedance and the magnetising admittance.
For the example 50Hz transformer shown, the magnitude of magnetising current is 12mA, 2.9% of rated current. Magnetising current is a component of primary current in a loaded transformer.
You might at first think that the magnetising impedance Zm is purely inductive, but that would make it lossless and nothing is lossless. In the example case, the phase of Zm is 74Β°, Zm=5556+j19213Ξ©.
Magnetising force is given by \(mmf=n(I_p +0.012 \angle -74° β \frac{I_s}{n})=n 0.012 \angle -74Β° \text{At/m}\).
Rated load
So, when rated current flows in the secondary, it induces a voltage component in the primary winding that opposes the voltage induced in the primary by the magnetising current component, so more primary current flows⦠rated primary current in a zero leakage scenario.
Print the diagram and annotate it with a pencil, and work through Lenzβs law and the direction of current. Sure, I could have done it, but you will learn more by working through the solutions, you will remember it better, and get confidence in your growing analytical capability.
So, the primary current under rated load is the load current divided by the turns ratio, plus the magnetising current. In this example, Ip=0.416-0.012β -74Β°.
Why does the core not saturate?
You need to calculate the net magnetising force by adding the primary and secondary magnetising force components. In this case, recalling that Is=Ip/n for our scenario, \(mmf=n(I_p +0.012 \angle -74° β \frac{I_s}{n})=n 0.012 \angle -74Β° \text{At/m}\), the same as the no-load magnetising force.
Note that when leakage inductance and winding resistance are factored in, loaded magnetising force is usually a little less than no-load.
If load current does not cause saturation, what does?
Two common causes:
- operating at lower that rated frequency; and
- operating at higher than rated voltage.
Because the B-H response is non-linear, a small increase in primary voltage creates a disproportionate increase in core less (due to higher flux density).
But my guitar amp can be driven to transformer saturation!
Sure, it is being driven to higher voltage and or lower frequencies than the design point, both of which contribute to saturation. Changing the load impedance does not directly cause magnetic saturation.
My ferrite cored EFHW transformer is easily saturated!
Probably not. Naive users often incorrectly blame overheating of the ferrite core beyond the Curie point as magnetic saturation.
Conclusions
- Lenzβs Law is key to understanding.
- Increasing primary voltage or lowering frequency can cause magnetic saturation.
- Increasing load current alone is unlikely to cause magnetic saturation.
- Other non-linear behavior is often wrongly attributed to magnetic saturation.
via Hackaday: Broadcast TV Simulator Keeps the Nostalgia Flowing
ARRL Day in the Park on Saturday
From W5XX:
The Jackson ARC invites you to this yearβs ARRL Day in the Park this
coming Saturday from 9:00 am until 2:00 pm at Old Trace Park.Β The folks
at Ridgeland Parks and Recreation graciously allowed us to use their
Recreation Center adjacent to the main parking lot. This will be a fun
time of fellowship and food (Dutch Treat from Food Truck).Β Β At noon
there will be a few comments by W5XX followed by multiple door prizes.
In addition, Flea Market tables will be available, or you can tailgate
in the parking lot.Β For those interested, the Mississippi State Fair
will be open for βafter Day in the Park fun and games.β
Old Trace Park is located at 422 Post Road in Ridgeland. To get there
follow the signs to the Bill Waller Craft Center on Rice Road and then
continue on Rice Road a short distance until you get to a stop sign at
the intersection with Post Road.Β Take a right on Post Road and Old
Trace Park will then be the second right.Β The Rec Center will be on the
right side of the large parking lot as you drive in.Β For further
information contact AK5J at cell 601-709-6740Β or emailΒ ak5j@arrl.net.Β Β Β
Talk-In: 146.64 (77 Hz) linked to 146.76 (77 Hz)
Best 73 de W5XX