A Stroudsburg teens’ passion for radio

[Stroudsburg, Monroe County, PA (WBRE/WYOU)] In this week’s Here’s to You Kid segment, 28/22 News met a young ham radio operator. It’s not only his hobby, what he does also involves helping save lives.

14-year-old Samuel Thrall, W3GZ,  is a member of the Eastern Pennsylvania Amateur Radio Association (EPARA.) He passed three levels of the FCC Amateur Radio Licensing exam and now helps at the Monroe County Public Safety Center.

What interested him in ham radio in the first place is simple. “The scientific aspect of it is very interesting because it’s a technology we use on a daily basis. Our phones are all powered by radio just with computers built into them,” Samuel explained.

…read more and watch the video

As a ham radio operator, Lacy, of Middleburgh, had interesting perspective on Boston Marathon

[Middleburgh, MA] There are an estimated half a million spectators along the Boston Marathon course in any given year. If you’ve run the race, you know what a half-million voices stretched over 26.2 miles of Massachusetts roads sound like.

Of the over 9,000 volunteers that work Boston, over 300 serve as the voice of the marathon in their own way, but also serve as the eyes and ears. For the last two years, Matt Lacy of Middleburgh has been one of them. On Monday, he took up his assigned station at Mile 11 as one of the amateur (ham) radio operators who play an important role from start to finish by providing a communication network that supplements the other public safety personnel and resources vital to this massive enterprise.

“For the ham radio folks, it’s the premiere public service event, the chance for us to get the experience doing one of these events, having to report to whatever levels we need to, working within the confines of whatever section of the course we’re on,” Lacy said on Wednesday.

…read more

TAG students launch solar-powered balloon

[Iowa Falls, IA] Riverbend Middle School TAG (Talented and Gifted) students launched a solar-powered balloon on April 5 from the school, after a presentation and help from amateur ham radio operator Jim Emmert of Pella. The balloon named PENS-p22 traveled across Iowa, Illinois, Indiana, Kentucky, Tennessee, Virginia, North Carolina, the Atlantic Ocean, Morocco, Algeria the Mediterranean Sea, Italy, and the Adriatic Sea.

“I am constantly on the lookout for guest speakers, fascinating projects or unique things that we could learn about,” TAG teacher Amanda Fjeld said. “I value exposing students to new topics and projects of any kind. I am constantly brainstorming ideas and often ask others for engaging project ideas. My friend Jen, who is from Pella, told me about Jim’s Solar Balloon program, so I reached out to him. I was especially excited because I lack knowledge in the world of solar technology and weather patterns but want to expose students to more science-related opportunities.”

Emmert is a retired teacher who lives in Pella and travels to different schools teaching students about amateur radio, earth science, balloons, and GPS technology. He also launches Pico balloons and gives predictions and tracking to the students.

“Our students spent about three hours on the morning of April 5 learning and launching the balloon,” Fjeld said. “It was one of the few times I have had all of the students in TAG in 6th, 7th and 8th grade come together on one project, so it was encouraging to see them interact and work together.”

…read more

As outlined in this previous post, there was a TEP (Trans-Equatorial Propagation) opening on the 144 MHz band between Namibia and Greece on the 31st of March 2024. As news spread that SV8PEX had been heard over 6500kms away in Namibia, more stations were active on the evening of the 1st of April.

This time, there were paths from Namibia to Greece, Italy and Malta and SV8PEX, 9H1TA and 9H1PA managed to complete contacts.

Alex, SV1NZX reports the following... "Tonight ends an exciting night for 2m #TEP QSOs - V51WW worked 9H1PA, 9H1TX and SV8PEX as well as receiving 4-5 other Italian stations in JN70, JN80. SFI measured at 125, K/A index at 5-8 and 1, all QSOs in Q65b, 30/60s."

This is a screen grab from SV8PEX in Greece...

This screen grab below is from V51WW and shows some of the exchanges with IK7UXW and IZ8EDJ  in Italy.

The screen grab below is from David, 9H1TX in Malta...

9H1TX writes... "Just finished my first TEP 2M qso with V51WW. I am totally closed to south but i elevated the system at 8 deg and was lucky to get his signal."

Analysis... As the map shows above, both stations are about equidistant from the Geomagnetic Equator and are crossing it at right angles, an important consideration for TEP signals at 144 MHz.

V51WW in Namibia is using 100w into a horizontal 9-element yagi 12m above ground level which is a pretty modest station. It shows that this TEP path to Europe is probably there a lot more often than people realise but the problem is that there weren't any stations in Africa to attempt a contact.

It would be interesting to see how far east and west in the Mediterranean the signal from V51WW can reach? How far from the 90 degree right angle at the Geomagnetic Equator can the 144 MHz signal go before it becomes impossible? EA6? IS0? 5B4? TA? SV5? SV9?

The Mediterranean is also an excellent location for tropo ducting. How far will that carry the signal north?

Are there any other stations at the southern end of the TEP zone? ZD7 (St Helena) to Spain seems an obvious one. Other paths?

It would be good to see more TEP reports from Europe to Africa on 70 MHz, 88-108 MHz and 144 MHz.

Links...

1) See my 144 MHz page for plenty of reports of other TEP contacts.

I’ve been gradually building my QO-100 ground station over the last few months and have had the receive path working for some time now. One of the things I really miss with the Funcube Dongle Pro+ (FCD) SDR is a real VFO knob for changing frequency.

My QO-100 Node Red dashboard is configured so that I can have the FCD track the uplink frequency from the IC-705 but, sometimes I use the FCD without the IC-705 in the shack and so a physical VFO would be handy.

Many years ago when I lived in France (F5VKM) I had a Flexradio Flex-3000 SDR, a great radio in it’s time and one that gave me many hours of enjoyment. One addition I bought for that station was a Griffin Technology Powermate VFO knob. It worked extremely well with the PowerSDR software for the Flex-3000 and I used it for many years.

Many years later I’m back in the UK and much of my equipment is packed away in the attic, including the Griffin Technology Powermate VFO.

I decided to dig it out and see if I could get it working with GQRX SDR software. Sadly I couldn’t get it working with GQRX however, I did find a way of getting it working with Node Red and thus could add it to my QO-100 Node Red Dashboard and then control GQRX with it via a simple Node Red flow.

Plugging the Powermate VFO into my Kubuntu PC it wasn’t immediately recognised by the Linux O/S. After a little searching I found the driver on Github. I added the PPA to my aptitude sources and installed the driver using apt.

https://launchpad.net/~stefansundin/+archive/ubuntu/powermate

Once installed the default config for the Powermate device is to control the default audio device volume. To make the device available for use as a VFO knob you need to change the configuration so that the default setting is disabled. To do this is relatively easy, just edit the config file using your favourite command line editor (Vi/Vim in my case) and add the following entry.

vi /etc/powermate.toml

# Entry to control HDMI volume with Powermate
#sink_name = "alsa_output.pci-0000_01_00.1.hdmi-stereo"

# Set powermate not to work with volume control
sink_name = ""

As shown above, comment out the default “sink_name” entry (Yours may be different depending on audio device in your PC) and add in the Powermate “sink_name” entry that effectively assigns it to nothing.

Once this is done, save the file and exit your editor and then reboot the PC.

Next you’ll need to install a small program called evtest.

sudo apt install evtest

To check the evtest program has installed correctly, plugin your Powermate VFO to any available USB port and run the following command in a terminal.

evtest /dev/input/powermate

Turning the Powermate knob you should see output on the screen showing the input from the device. You should also see BTN events for each press of the Powermate device.

Input driver version is 1.0.1
Input device ID: bus 0x3 vendor 0x77d product 0x410 version 0x400
Input device name: "Griffin PowerMate"
Supported events:
  Event type 0 (EV_SYN)
  Event type 1 (EV_KEY)
    Event code 256 (BTN_0)
  Event type 2 (EV_REL)
    Event code 7 (REL_DIAL)
  Event type 4 (EV_MSC)
    Event code 1 (MSC_PULSELED)
Properties:
Testing ... (interrupt to exit)
Event: time 1685816662.086666, type 2 (EV_REL), code 7 (REL_DIAL), value -1
Event: time 1685816662.086666, -------------- SYN_REPORT ------------
Event: time 1685816662.318638, type 2 (EV_REL), code 7 (REL_DIAL), value -1
Event: time 1685816662.318638, -------------- SYN_REPORT ------------
Event: time 1685816662.574615, type 2 (EV_REL), code 7 (REL_DIAL), value -1
Event: time 1685816662.574615, -------------- SYN_REPORT ------------
Event: time 1685816663.670461, type 2 (EV_REL), code 7 (REL_DIAL), value 1
Event: time 1685816663.670461, -------------- SYN_REPORT ------------
Event: time 1685816664.030421, type 2 (EV_REL), code 7 (REL_DIAL), value 1
Event: time 1685816664.030421, -------------- SYN_REPORT ------------
Event: time 1685816664.334389, type 2 (EV_REL), code 7 (REL_DIAL), value 1
Event: time 1685816664.334389, -------------- SYN_REPORT ------------
Event: time 1685816665.334255, type 1 (EV_KEY), code 256 (BTN_0), value 1
Event: time 1685816665.334255, -------------- SYN_REPORT ------------
Event: time 1685816665.558230, type 1 (EV_KEY), code 256 (BTN_0), value 0
Event: time 1685816665.558230, -------------- SYN_REPORT ------------
Event: time 1685816666.030161, type 1 (EV_KEY), code 256 (BTN_0), value 1
Event: time 1685816666.030161, -------------- SYN_REPORT ------------
Event: time 1685816666.182151, type 1 (EV_KEY), code 256 (BTN_0), value 0
Event: time 1685816666.182151, -------------- SYN_REPORT ------------

At this point you’re ready to stop evtest (CTRL-C) and then create the following little BASH shell script that Node Red will run to collect the O/P from the Powermate USB device.

#!/bin/bash

###############################################
# Griffin Technology Powermate control script #
# for Node Red.                               #
#                                             #
# 04/06/23 - M0AWS - v0.1                     #
#                                             #
###############################################

VAL="1"
echo "STEP-1Hz"

/usr/bin/evtest /dev/input/powermate | while read LINE 
do
   case $LINE in

      *"(REL_DIAL), value 1") echo "$VAL"
           ;;

      *"(REL_DIAL), value -1") echo "-$VAL"
           ;;

      *"(BTN_0), value 1") case $VAL in

                              "1") VAL="10"
                                   echo "STEP-10Hz"
                                      ;;

                             "10") VAL="100"
                                   echo "STEP-100Hz"
                                      ;;

                             "100") VAL="1000"
                                    echo "STEP-1Khz"
                                       ;;

                             "1000") VAL="10000"
                                     echo "STEP-10Khz"
                                         ;;

                             "10000") VAL="1"
                                       echo "STEP-1Hz"
                                          ;;
                              esac
                                 ;;
        esac
done

Once the BASH script is copied and pasted into a file called powermate.sh you need to make it executable by using the following command.

chmod 700 ./powermate.sh

If you now run the shell script in a terminal you’ll see a similar output to that shown below from the device when used.

./powermate.sh 
STEP-1Hz
-1
-1
-1
1
1
1
STEP-10Hz
10
10
10
-10
-10
-10
STEP-100Hz
100
-100
-100
STEP-1Khz
1000
STEP-10Khz
STEP-1Hz
1
1
STEP-10Hz

As you can see above the shell script outputs a positive or negative number for VFO tuning and changes the VFO step size each time the Powermate is depressed.

Getting this output from the BASH shell script into Node Red is really simple to achieve using just 3 or 4 nodes.

In the Node Red development UI create the following nodes.

The first node in the flow is a simple inject node, here I called it trigger. This sends a timestamp into the next node in the flow at startup to set the flow running.

The Griffin Powermate node is a simple exec node that runs the script we created above.

Configure the node as shown above and connect it to the inject node that’s used as a trigger. Note: Change “user” in the Command field shown above to that of your username on your Linux PC)

Once done create the third node in the flow, a simple switch node and configure as shown below.

The switch node has two outputs, the top one is a text output that is fed into a text field to show the current step size of the Powermate device and the lower output is the numeric output that must be fed into your VFO control flow so that the VFO value is incremented/decremented by the amount output by the Powermate device.

I’ve found the Griffin Technology Powermate USB device works extremely well with Node Red and GQRX that I use for controlling the FCD SDR radio and it’s now part of my QO-100 ground station build.

As shown above you can see the Powermate Step size at the bottom of the dashboard, this text changes each time the Powermate device is depressed and will set a step size of 1Hz, 10Hz, 100Hz, 1Khz, 10Khz in a round-robin fashion.

The next stage of the build is the 2.4Ghz transmit path. I now have all the necessary hardware and so this part of the build can finally commence.

More soon …

I sought a low power bench audio PA to use for guitar preamplifier development. This brick measures ~ 18 x 11 x 8 cm and delivers 12 clean Watts power into an  8 Ω load. On the front panels 3 RCA jacks provide regulated +/- 17 VDC plus a signal ground connection. Additionally, the signal input jack lies on the front panel. The rear panel sports a speaker jack, fuse and the AC mains input.

Above — The +/- 17 volt rail regulator/filter circuits. My rectifier included a full wave bridge and the main reservoir capacitors = 4700 µF.  I re-purposed The main Hammond chassis from some old project and this entire project falls under the low cost category since most of the parts were ancient specimens from my collection.

Above — Popcorn PA schematic. This is a slightly tweaked version of this Polytone-inspired PA. I recommend this PA over my original version since it offers way less distortion.

The small signal transistors = 2N4401/2N4403 - a pretty decent general purpose BJT I use from DC to HF. The input pair feature some emitter degeneration via a 100 Ω trimmer potentiometer. If you lack a trimmer pot, place a 49.9 to 68 Ω resistor on each BJT emitter instead.  

I ran out of BD140s plus sought a VAS with an fT of > 150  MHz, a low Cbe and a hfe as high as possible. VAS transistor choice seems to shrink every decade. Gone are the luscious  high voltage, high current, high beta offerings from companies such as Toshiba or Sanyo. For example, the KSA1381/KSC3503 or 2SC2911/2SA1209. Yes, these are still available from online auction sellers, but they seem very expensive and the whole bootleg part worry looms heavy. The BD139-140 seem the only low cost, readily available choice for a low budget PA like mine. The BD139/140 pair specs also widely varies - and some are just garbage. I now get mine from Digi-Key and test a couple to confirm they are OK.

In the end, I placed two 2N4403 BJTs in parallel with 10 Ω current sharing resistors for the VAS. This worked OK. Guitar amps are generally not hifi amplifiers giving ultra low distortion. Some might classify as hifi, but that is the exception. I avoided current sources, driving the VAS with a emitter follower and other distortion lowering techniques. 

The virtue of this PA = easy to build, easy to debug and sounds very good for the parts count. If you scratch build a complicated HiFi PA, you suffer a high probability of failure. Especially when current limiting circuitry and 2 current sources that work together with negative feedback go into your circuit. Often enough, your first sign something is wrong comes in the form of smoke; and by the time you figure out why, you may have destroyed some parts.

Above — FFT of the Popcorn PA. All harmonics are down at least 70 dBc. I tweaked the input pair 100 Ω trimmer to crush the second harmonic. Some of this spurious output comes from IMD in the TIP142/147 pair. In a PA, distortion can arise from many points along the signal path. I'm quite happy how this particular PA turned out.

Across the base inputs of the Darlington final pairs, I measured 2.064 VDC. Three rectifier diodes seemed to eliminate any detectable crossover distortion ( a dominant source of distortion in many PAs).

If you listen to a  guitar amp that lacks enough forward PA base bias and suffers crossover distortion, you'll hear a faint, fuzzy sideband sound along with your main guitar sound. You really hear this when playing single, sustained note phrases. This popcorn PA sounds clean & punchy with no hum except with single coil pickups.

Above — I built this version of my PA first. The BD-139/140 emitters get 120 Ω resistors so they don't need a heat sink and hopefully won't burn up if I made a mistake. I measured DC voltages, calculated current by voltage drops across selected resistors — and also tested it with a signal generator and dummy load. Only 2 diodes drops are needed to properly bias the BD139/140 pair.

With the amp working well, I then pulled the BD139/140 off the main board and wired up the chassis mounted TIP142/147 after adding 1 more diode to set the correct PA idling base bias. Finally, I added the current feedback loop. I chose the 7K5 Ω resistor during listening tests.

Click here for my guitar related index.