This is a very cool video. I even liked Helge's creative use of AI for the narration. It was amazing that this old rig still works.
Thanks you Helge. And thank you to all the brave members of XU, who so valiantly risked it all in the fight against Fascism. See: https://en.wikipedia.org/wiki/XU
My grandfather was a lifelong radio enthusiast and ham radio operator. In his early twenties during World War II, he lived in the remote mountain village of Hjerkinn, working at the railroad station high above the treeline when Germany invaded Norway.
He joined the resistance movement and built radios using parts from a downed Luftwaffe aircraft—mainly the radio tube, as seen in the photos I’ve attached. With it, he secretly tuned into broadcasts from London. It was a risky and courageous act, but it kept him and others informed when access to truthful news was critical.
Later, he introduced me to the world of radio. As a kid, I spent hours scanning ham bands, police channels, and even unencrypted cellphone calls. I was probably way too young to be listening to some of it, but in the pre-smartphone era, it felt innocent enough. That early exposure sparked a lifelong passion for electronics and radio—one that still defines me today.
A few weeks ago, I visited my mom and saw one of the wartime radios he built. I thought this group might appreciate it—not just as a relic, but as a story of ingenuity, resistance, and the enduring magic of radio.
Thanks to Jim VE1KM for alerting us to steeljo's story. I told Jim that that Nazi tube is reminder of just how dangerous this all was for his grandfather.
Here are two more great museum visits by Helge LA6NCA. In these two he visits Ragnar LA1UH.
Ragnar has a lot of maritime experience, so we see a lot of older ships' radios. But his interest in the radio art is much broader and we also see a lot of other kinds of gear:
-- Wow, a "travel radio" in a suitcase from 1927. Was this the idea that later lead to the Parasets of WWII?
-- Lots of "Stay Behind" gear from the Cold War. That "Africa" receiver (that never made it to Africa!) is very interesting.
-- We see an ART-13 with autotune, ANGRC-9s, several ARC-5 command sets. I was hoping Raganar would fire up a Dynamotor, but no.
-- I spotted a Galaxy V transceiver. I have the VFO reduction drive from one of these in my homebrew 15/10 rig.
-- We see several variometers in the emergency (500kc?) maritime transmitter. I used a variometer in my super-simple ET-2 transceiver (with an N0WVA receiver).
-- Lots and lots of tubes.
Ragnar says he himself is of 1944 vintage. I hope some "stay behind" provisions have been made for these amazing museums.
Brace yourselves. This is just too much, too much radio history, too much cool stuff. We are into ham radio sensory overload territory here. The rigs, the radios, the radioactive stuff (including tubes!). Lots of Whermact stuff. A Chinese receiver. Tesla coils and Faraday shields. Much more.
Thanks to Helge LA6NCA for alerting us to this and for shooting these videos. And thanks to Jens OZ1GEO for putting this magnificent collection together. I hope they find sometplace to keep this all together so that future generations can benefit from it.
George WB5OYP points out there is more from Jens here:
FB Helge. This is really cool. I didn't realize until I saw the schematic at the end that he was on 3579 kHz -- that is the old color-burst frequency, and now the frequency of the Color-burst Liberation Army.
It was challenging to do this without sidetone. But there appears to be a bit of room left in the matchbox -- could he squeeze in a few more components for a rudimentay sidetone? Maybe just a piezo buzzer across the key?
Here's another great video from Helge LA6NCA. This is a follow-up to his Altoids Spy Transmitter project. Really well done. Hack-A-Day called this receiver "regenerative" so naturally I was disappointed, but when I watched I realized that it is NOT a regen but is instead a direct conversion receiver. TRGHS. All is right with the world. Thanks Helge! 73
Helge is an amazing homebrewer. Check out the shack. Note the R-390 and the Tek 'scope. Watch how Helge designs his rig. Watch him check the 3-D printed coil and the variable caps for resonance. Most of all, watch his happiness when the new transmitter works. I just wish he would have showed us some OM complaining that he was on the "wrong" sideband. FB Helge! Thanks.
But until now, I never built one. Recently, Dean KK4DAS and the Vienna Wireless Makers group have been building a Direct Conversion receiver. Their receiver uses an Si5351 as the VFO, but of course Dean and I have decided to try to do things the hard way by building non-digital VFOs. At first we just came to the conclusion that my earlier Ceramic Resonator VFO wasn't much good (it drifted too much). This led us into standard Colpitts and Armstrong VFOs, and the fascinating world of temperature compensation. Then I remembered the Polyakov circuit -- this would allow us to use a 3.5 MHz VFO on the 7 MHz band. Lower frequency VFOs are easier to stabilize, so I started building my first Polyakov receiver. You can see the results (on 40 meters) in the video above.
I started working with a circuit from SPRAT 110 (Spring 2002). Rudi Burse DK2RS built a Polyakov receiver for 80 and 40 that he called the Lauser Plus. (Lauser means "young rascal" or "imp" in German.) For the AF amplifier, I just attached one of those cheap LM386 boards that you can get on the internet. With it, I sometimes use some old Iphone headphones, or an amplified computer speaker.
The Polyakov mixer is a "switching mixer." The book excerpt below shows how I understand these circuits. The enlightenment came from the Summer 1999 issue of SPRAT (click on the excerpt for an easier read):
Leon's circuit shows us how a simple switching circuit in which the switches are controlled by the VFO can result in an output that has the sum and difference components. That is the hallmark (and most useful part) of real mixing. Remember -- we say that mixing happens in non-linear circuits when the passage of one signal depends on what is happening with the other signal. A switch is as non-linear as you can get! And that switch is being controlled by the VFO.
In a Direct Conversion receiver we usually run the VFO at the operating frequency. This results in audio just above and just below the operating frequency.
The Polyakov Direct Conversion circuit is a bit different. It has the switches (the diodes) turned on twice each cycle: When the VFO voltage goes to a positive peak, this turns on one of the diodes. When the VFO goes to a negative peak, this turns on the other diode. So in effect the switch is being turned on TWICE each cycle. So with the Polyakov you run the VFO at HALF the operating frequency. For a DC receiver designed to run around 7.060 MHz, you build a VFO at around 3.53 MHz. This has some immediate advantages. My favorite is that it is easier to get a VFO stable at a lower frequency. It is easier to stabilize a VFO at 3.53 MHz than it is at 7.060 MHz.
When you open that SW 1 switch in the Lauser Plus, you no longer have a Polyakov mixer. Now you just have a diode mixer. It will be opening and closing once each cycle at the VFO frequency. DK2RS used this to cover not only the 40 meter band (in Polyakov mode) but also the 80 meter band (in single diode detector mode). That is why DK2RS has that big variable capacitor in the input circuit -- that LC circuit needs to tune all the way down to 3.5 MHz and all the way up to around 7.3 MHz. (I used a coil of about 6.5 uH to do this.)
With just one diode and operating at 80 meters, it works, but not as well as it does in the Polyakov mode on 40. I can pick up 80 meter signals, but in this mode there seems to be more of an "AM breakthrough" problem. "Experimental Methods in RF Design" on page 8.11 describes what is going on (the last sentence is most relevant here):
Here are some very good links with information on the Polyakov receiver:
LA8AK SK: http://www.agder.net/la8ak/ Almost seventeen years after his death he continues to help his fellow radio amateurs through his web sites. TNX OM! FB!
Discussions of old military radio gear are dominated by talk of U.S. radios. Yesterday in the comments section of the SWLing Post I found two interesting videos about German WWII equipment. Above you can see LA6NCA's receivers. Below there's a video of a Luftwaffe receiver with an amazing capacity for really rapid frequency change.
Click on the link to check out Tor's very FB and artistic video about his homebrew IRF-510 amplifier. Very Nice. Also, check out Tor's FB SolderSmoke hat.
Tore Bonderudtåjet LB4RG tells us that he is a SolderSmoke listener, and that the old tradition of hams soldering their fingers together continues to be practiced in Norway. Here are some pictures of his latest efforts. This is an SWR bridge project. Thanks Tore! Careful with the fingers OM!
A video about the Kon-Tiki expedition got us wondering about how you could generate hydrogen gas for an antenna balloon while on a raft at sea. (That's the kind of question that keeps Knack victims up at night.) This led us to the Gibson Girl rescue radio. This morning I found a fascinating web site that gives the long, multi-country history of the curvaceous rescue rig:
Back in July we shared a very nice video sent to us by Rupert G6HVY on the radios used by the Kon-Tiki expedition. Many of us had questions about the device used by the intrepid radio operator to generate hydrogen gas (for the antenna balloon) while on the high seas. Mike Herr WA6ARA supplied the answer: 1200 grams of Calcium Hydride crystals. This was part of the WWII rescue radio set CRT-3 (aka the Gibson Girl). Fair Radio Sales occasionally sells this intriguing device: https://www.fairradio.com/catalog.php?mode=search&keywords=hydrogen&submit.x=21&submit.y=8 And here is great site with more details on the other antenna supports in the Gibson Girl set, including a ROCKET LAUNCHED KITE! https://billboyheritagesurvey.wordpress.com/2012/01/17/war-kite-the-gibson-girl-kites/
Just found a short Youtube QRP video which is quite fun. It's of the radio side of Thor Heyerdahl's cross-Pacific Kon-Tiki raft expedition in 1947, operating /MM with 7 watts. I found a longer description of what they had and what they did - including a thrilling tale of drying components on coral reefs while they desperately tried to make contact having washed up on an island - but not of the unusual parrot incident with a hydrogen balloon-lofted antenna during the voyage. That's only in the video.
It's all gripping adventure radio stuff, and shows what HF and a bunch of tubes could do before the digital satcom age.
"The expedition used call sign LI2B and carried three watertight radio transmitters. The first operated on the 40 and 20 meters, the second on 10 meters and the third on 6 meters. Each unit was made up entirely of 2E30 vacuum tubes providing 10 W of RF input. As an emergency backup, they also carried a German Mark V transceiver originally re-created by Britain's Special Operations Executive in 1942. Other equipment included a hand-cranked emergency set of the Gibson Girl type for use on the maritime bands, a special VHF set for contacting aircraft and two British Mark II transmitters. The Kon-Tiki also carried a National Radio Company NC-173 receiver. Dry batteries and a hand-cranked generator supplied the power."
I got the Si5351 portion of the new rig going today. I used an Arduino program from Thomas LA3PNA. It is relatively barebones, without a lot of bells and whistles, but it does just what I need: it puts out a fixed BFO frequency and a variable VFO frequency, and displays the resulting transmit frequency. Thanks Thomas, and thanks to Jason, NT7S, for his work on the Arduino libraries that make this all possible.
It is very simple: Just an Arduino Uno with the Si5351 board sitting above it on a proto board that Pete sent me (thanks Pete!). You can see the rotary encoder on the panel, and the 10K pot to set the brightness of the back-lit display. I put the Arduino USB port on the front to make it easier to update the software, change the BFO freq. etc. I'm going to use another cigar box wooden box for this projects, so the VFO/BFO front panel board was sized with that box in mind.
Wow, what a beautiful piece of work! And a fascinating story behind it, with hints of wartime romance... Thanks to Mike AA1TJ whose very eclectic reading (Czech tech mags!) led us to this. Thanks also the Crypto Museum. Here is the link:
