Pete N6QW's "Last Ditcher" CW Thermatron Rig -- Frank Jones would approve. A new installment of the FMLA series?

I like this rig.  Perhaps I like it too much.  I find myself plotting to build it myself.  I mean, I have tubes.  I have a bunch of old parts (many sent to me by Pete himself).  

Alas, I have to fight the temptation.  I have to tell myself that this is for CW (a mode that I have come to be impatient with).  And it is a thermatron rig that requires potentially lethal voltages. 

Still, Pete's construction technique is really neat.   It combines old style slat-board construction with modern copper clad boards.  Frank Jones would approve.  

I think we need someone to write another episode of the FMLA series, this one using Pete's build.  And maybe featuring Pete himself. 

Here is some needed background info on Frank Jones and the FMLA articles: 

https://soldersmoke.blogspot.com/2021/07/summer-reading-for-homebrewers-frank.html

I look forward to hearing from protential authors.  If the new articles are good,  I will put them on the SolderSmoke blog.

Helge LA6NCA's Norwegian Paraset

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 

A Quick Review of "Open Circuits" by Eric Schlaepfer and Windell H. Oskay

Wednesday's post about this book caused me to pull it off my shelf and to take another look.

Highlights from the SolderSmoke perspective: 

Page 34  Glass Capacitors.  Phil W1PJE left me some. 

Page 48  Ferrite Beads.  Underrated.  People often don't think they will work. 

Page 66 Glass-Encapsulated Diodes.  Yes, 1N4148's in our Direct Conversion Receiver. 

Page 70 2N2222.  In a metal can. 

Page 72 2N3904.  We use them so often. 

Page 90 Color LEDs.   The Green Hornet beacon in Cap Cana, Dominican Republic. 

Page 116  Electromagnetic Relay.   We use them a lot. 

Page 142 DIP sockets  I recently struggled with them with my NE602 chips. 

Page 182  12AX7.    Thermatron! 

Page 186 Cathode Ray Tube.   I have some. CuriousMarc recently fixed one. 

Page 190 Mercury Tilt Switch. I had one as a kid.  You can change a reflector to a director.  

Page 196  Dipped Silver Mica Capacitor.    We use them.  A lot.  Sometimes as NP0 caps. 

Page 198  IF transformer.  S-38E.  HQ-100.

Page 206 - 207 Point Contact Diode and Germanium Diodes.  Crystal radios. Great fun. 

Page 210 Windowed EPROM. Was this the Rom chip in the TW-100s? 

Page 212 Core Memory.  Rope!   As used in the Apollo spacecraft. 

Page 228 Single-Side Printed Circuit Boards.  Almost (but not quite) Manhattan. 

Page 238 MicroSD Card.  I have one in my Drone. 

Page 262 Crystal Oscillator.     TCXO?  In a can?  As in Dean's WSPR transmitter? 

What do you guys think? 

CuriousMarc Repairs the French Oscilloscope of His Youth -- ACHTUNG!

It was very cool to watch CuriousMarc go back and repair the French Oscilloscope that he used as a kid. 

I was reminded of my work on a Tek 465 scope.  There is a LOT of high voltage around those CRTs.  I needed to measure the HV on my Tek 465 -- Alan Wolke W2AEW lent me a high voltage probe. Thanks again Alan.  I eventually gave up on the Tek 465 but that was because mine had plug-in transistors.  Yuck -- one bump of the elbow during troubleshooting and you could easily inject new problems into the broken machine. 

Marc's work also caused me to think about working on the HAMEG 10 MHz scope that I have in the shack.  Also there is the older Eico scope that was so bad and so limited in bandwidth that it has been banished to the basement.  But I must say, watching Mark move around high voltage made me realize why so many of us have migrated to solid-state scopes.  I have modern Rigol scopes in both my shacks. 

As with Mr. Carlson, I must say that Marc should be more careful with energized gear and capacitors that hold their charge.   Marc seems to think that those insulating gloves protect him from HV, but he still grabs that beast with both hands and makes skin to metal contact with at least one arm.  Yikes!  Don't do that!  Volts jolt but mils kill OM!  One hand behind your back!  Marc does recognize the danger, and displays this sign at least three times during the video.  (Marc is obviously NOT a dummkopf!)     

Google Gemini said this about the sign: 

The language is German (though it is a bit grammatically jumbled and misspelled).

Translated to English, it roughly means: "Is it not for work by blockheads!" or "Is this not for use by fools!"

A Quick Breakdown

The phrase looks like a slightly mangled variation of a classic piece of old internet joke-lore known as "Blinkenlights."

Back in the early days of computing, tech rooms often had mock-warning signs posted in broken, comical German (often called "Mock-German" or "Germlish") to warn non-technical people not to mess with the machines.

If you are looking at a quirky warning sign or an old tech joke, the proper full phrase usually goes something like this:

"Achtung! Alles Lookenspeepers! Das computation-machine ist nicht für gefingerpoken und mittengrabben! Ist easy schnappen der springenwerk, blowenfusen und popencorken mit spitzensparken. Ist nicht für gewerken bei dummköpfen!"

In short: "This is serious equipment—no touching, and it's definitely not meant to be operated by fools!"

----------------------------------------------------

And be sure to check out the oscilloscope music as seen by Marc's old scope: 

https://www.youtube.com/watch?v=JCukVSqoZyI

Radio Receivers -- 1942 Training Film -- Crystal Sets to Superhets

This 17 minute film provides a good but simplified description of the state of the art at the start of World War II. 

--  The description of how a signal gets to the input coil of a receiver is quite good.  Imagine if that coil had no good ground, and no counterpoise.  We see the importance of the counterpoise in this video: https://soldersmoke.blogspot.com/2023/03/an-antenna-for-high-school-direct.html

-- I like the repeated demonstration of the reality of envelope detection.  Too often people have bought into the idea that envelope detection is not real, and that some form of mixing using the carrier in lieu of the local oscillator is what is really happening.  That is just not true.  Envelope detection as described in this film is real. 

-- The description of mixing is very simplistic.  They describe the generation of the difference product, but not the sum.  But hey, the film is only 17 minutes long!  It takes a lot longer than that to fully describe mixing (ask me how I know!).  

-- At the very end, there is a shout-out to the BC-348.  FB. 

Homebrew Cylindrical Variable Capacitors: What the Steering Wheels are Controlling in Danny's Regen Receiver

Grayson KJ7UM asked a very good question about Danny ON1MWS's regen receiver:  What were those two very cool "steering wheels" actually controlling?.  

Perhaps because of our recent experience with Permeability Tuned Oscillators, I kind of assumed that we were talking about some form of variable inductor.  But no, I was wrong.  They are for homebrew variable capacitors.  That just makes it a lot cooler.  

Danny explains: 

Dear Grayson,

Tnx for the compliments. I used to build normal square boxes while I was a mechanic in a light advertisement factory. We had a one hour lunch break and were allowed to work for ourselves during the break. But I left that firm in 2019, as a consequence I had to find a way to build rigs without custom square boxes… the result is wood, tin cans of all sorts and a simple ground plate. After posting my CW rig on the FB group ‘the art HAM radio homebrew’ in 2023, Steve Fabricant noted ‘It could be a radiosonde that they sent down from a saucer to detect intelligent life, and failed.’ LOL, I found that very funny actually. 

 

As for your question, all of my homebrew tuning capacitors have a shaft made off a M8 (about 8mm) threatened rod. The rod turns through a steel girder bracket. I am not sure how these things are called in English, but they are easy to find on the net and very cheap. The rod is the ‘ground’ of the capacitor. The ground plate is clearly visible in the pictures of the solid state regen and the ground plate is hidden under the wood in the tube regen. In the case of the tube regen, the left tube has an inner diameter of 10mm and the right one about 13mm. The right one is coarse and the left one fine tuning. Not sure about the capacitance. 30pF at most I think. The tube regen tunes from 7 to 7.25 Mhz so that's ok.

As you turn the rod the rod will shift in or out the metal tube. The tube is obviously the ‘hot’ side of the capacitor. The M8 rod moves 1.25mm for one turn of the rod. If memory serves me right the tube is 80mm for the tube regen, so we have a tuning gear reduction of 80/1.25= 64. The hot side is connected to the main tuning coil to create a tank circuit.

I did try different designs before but this is the best one. The tube/treaded rod capacitor is just as good as a commercial one. One thing I learned is that any friction must be avoided in a homebrew capacitor or it is useless in practice.

I am going to try to build a similar 400pF version for a homebrew crystal set as I wrote to Bill. It will be huge I guess.. I think I will need a 2”tube… But my current homebrew projects are insulating our house better as our natural gas prices are rising.

Like the way you call tubes Thermatrons. Yes, sound much cooler and more fitting for these beautiful devices. My ultimate aim is building a one band thermatron SSB exiter. No time for the moment.

Kind regards Danny.

This technique could prove very useful in homebrew projects.  We found it very difficult to source suitable variable capacitors for our direct conversion receiver.  That is why we went with the PTO circuit.  But this technique makes it possible to actually homebrew the capacitors.  FB Danny.  

Thanks Danny.  Thanks Grayson.

ANOTHER AMAZING Homebrew Station -- This one from Belgium -- ON1MWS

 

Those large "steering wheels" on the regen rig caught my attention, and I'm glad they did, because they led me to the sites of Danny ON1MWS. 

https://www.qsl.net/on1mws/

https://www.qrz.com/db/ON1MWS

Danny writes on his QRZ page: 

I'm especially interested in homebrewing my own station. everything from the power supply to the antenna is scratch-build. I have no commercial ham gear, nor do I use pre-fabricated kits or DDS chips.

My gear is a toy compared to a modern station. And it will never even come remotely close to commercial gear. However, the journey to learn how radio circuits work, improve the station and add capabilities over the years has been satisfying. R&D as amusement.

-----------------------------------

FB Danny!  Thanks for the rigs and web sites.  73  Bill N2CQR

The Coastwatchers -- Their Rigs and Their Islands

 

AWA Teleradio 3BZ used by coastwatchers during the war Source: Australian War Memorial (P01035 .006)

Here is a great site about the AWA 3BZ Wireless set: 

https://www.qsl.net/vk2dym/radio/3BZa.htm . 

AWA 3B SET

Here's a good article about the Coastwatchers: 

https://www.military.com/daily-news/investigations-and-features/2025/12/22/former-school-teacher-led-guerrilla-army-behind-japanese-lines-solomon-islands-and-helped-us-win.html

Guadalcanal 1943

I've been interested in the Solomon islands lately because my wife and I have been watching a YouTube video channel about a family living on Uepi island: 

 https://www.youtube.com/c/TheIslandLifeofUs 

Uepi is right on "the slot," near New Georgia. 

There are WWII remnants still visible (underwater) at Uepi: 

AI Overview

Uepi Island in the Solomon Islands is famous today for its World War II history, particularly its abundant, accessible WWII wreck dives (aircraft & ships) in Marovo Lagoon, a key battleground during the Solomon Islands Campaign, offering divers a tangible connection to the fierce fighting between US and Japanese forces. The area, near major WWII sites like Guadalcanal, features underwater artifacts like Japanese Zeroes and US Corsairs, with the modern Uepi Island Resort preserving these historical relics within its dive operations. 

Uepi's WWII Significance

• Location: Uepi is situated in the Marovo Lagoon, part of the Solomon Islands, which were central to the brutal Pacific Campaign of WWII.
• Wreck Dives: The waters surrounding Uepi are a "treasure trove" of sunken WWII aircraft (like P39 Air Cobra, Japanese Zeroes) and shipwrecks, making it a prime destination for historical diving.
• Preservation: The Uepi Island Resort actively manages and promotes responsible diving at these sites, emphasizing that removing artifacts is illegal. 

Key WWII Sites & Wrecks Near Uepi

• Wickham Harbour: Located near Uepi, this area contains significant WWII wrecks, accessible via boat trips from the island.
• Aircraft: Divers can find Japanese Zeroes, American Corsair fighters, and potentially B24 bombers, often in challenging conditions, with efforts to move some to cleaner areas.
• Marovo Lagoon: As one of the world's largest saltwater lagoons, it holds numerous historical remnants from the intense fighting. 

A VERY Interesting Old "Steam Punk" Homebrew Thermatron Rig -- Can You Suggest A Home for this Rig? (Video)

Oh man.  They got me at the breadboard, but there was so much more:  

-- A mercury switch

--  A homebrew variometer

-- A reading lamp

-- A specially made (and stored!) tuning tool and a mechanical pencil 

--  A CQ paper tape and tape reader! 

-- A front panel clock

-- Space for QSL cards on the front panel   

This is a really cool homebrew radio!  Can someone find a good home for this amazing device?  The video was posted only 1 month ago.  

SolderSmoke Podcast 261: Travel, AI-Apocalypse, ARRL Award, Amplifiers (with Claude) , Transcoms, Smoke released in DR, QRP, CW, MAILBAG

SolderSmoke Podcast #261 is available for download: 

Audio:  http://soldersmoke.com/soldersmoke261.mp3

Video:  https://www.youtube.com/watch?v=1rzw8lxBzRo

Alaska, Colorado, Dominican Republic

Opening:   Travel notes:    Pete to Denver.  Dean to Alaska.  Bill in the Dominican Republic. 

The future of the podcast.  We will embrace our NIMCEL status and fight on in spite of the AI Apocalypse.   Thanks to Peter VK3TPM, Hamilton KD0FNR, Sam AI7PR, Todd K7TFC  and the WayBackMachine for providing backup and transfer options for the blog. Google could end Blogspot at any time.    

Dean and Bill win the 2025 ARRL Technical Service Award.  Thanks to Bruce KC1FSZ for the nomination. And thanks to Bill Morine N2COP for letting us know.  91 receivers completed so far!  

SolderSmoke East was pleased to host Phil W1PJE, a distinguished MIT radio astronomer AND member of the SolderSmoke Direct Conversion Receiver Hall of Fame.   

Dean:   Amplifier design,  woes, triumphs, tribal knowledge.  And help from Claude. 

KK4DAS 100W MOSFET AMP

Pete:  Project X  -- The Transcom SBT-3,  Crossroads and Decisions. 

Transcom SBT-3

SHAMELESS COMMERCE DIVISION:   FIGHT THE AI-APOCALYPSE -- BECOME A PATREON SPONSOR.

GET BEZOS TO SEND US BEZOS BUCKS!  Use the Amazon link on the upper right.   

BUY PARTS AND STUFF FROM MOSTLY DIY RF. 

Bill: 

-- Smoke released in TWO RD06 finals.  Scrounged IRF-510s to the rescue.   

-- Working VK6 on 20 SSB.  

-- My old HW-101 -- inspired by Pete and by Will N5OLA.   

-- High frequency hearing loss and direct conversion receivers. 

-- Eleven contacts on 40 with the DC RX and a Tuna Tin 2. Mike Bryce WB8VGE came back to my CQ! First ever QSO with SolderSmoke DC receivers on both sides:  K1OA-N2CQR.  

-- Do real hams use ALC? Do we really NEED ALC? 

Mailbag: 

Who is the Project 326 Guy?  A British engineer resident in China for last 20 years. 

Steve EI5DD  Ham Radio Ireland magazine.  Hey -- Why no Irish DC RX builders? 

Paul K9ARF -- Thanks for the very kind e-mail about SolderSmoke. 

Rogier PA1ZZ -- Many nice videos and suggestions on blog backup. 

Grayson KJ7UM on the EF-50 valve (thermatron!) 

Bruce KC1FSZ  Four DC RX builders at the Wellesley Mass radio club. 

Chris KD4PBJ -- Long trip to pick up two directional beacons possibly for 630m or 2200m bands! 

Alan W2AEW did a Minimum Discernible Signal test on the DC RX.  FB! 

Mike WN2A  -- Many great comments on MDS in its various forms. 

Philippe F6GUH is a FB homebrewer.  

Mike EIOCL -- Always great to talk on the air with an old friend. 

Walter KA4KXX -- I checked into the Sunrise net!  With my HW-101!  Thanks Walter. 

Farhan VU2ESE -- Watched our interview with Phil W1PJE

Phil W1PJE was an SWL with an old Halli receiver.  VOA?  Boo!  But Radio Marti is BACK! Also, the hydrogen line from the cosmic dark ages has red shifted to... 7.1 MEGA hertz!  So LISTEN UP! 

Phil W1PJE with a Halli and the Haystack Observatory Dome

The Guy with the USB-powered X-Ray Machine -- The Identity of the Project 326 Builder

This morning a comment came in from Hong Kong/Shenzhen that explained who Project 326 is and why he was saying "tubes" and not "valves": 

--------------------

Thank you for featuring my video. Some background for you, I am a British engineer and have lived in China for over 20 years. I am resident in both Hong Kong and Mainland China (Shenzhen, which is just over the border from Hong Kong). I used the term vacuum tubes as most of the viewers are from the US and us Brits are fully conversant with both terms, but in the US, they are often less 'bilingual' in these kinds of phrases.

Hope that helps!

----------------------

It does indeed help a lot.  Please continue to make great videos like the one about the USB X-Ray machine.  

Here is the channel: 

https://www.youtube.com/@project-326

Britain's EF-50 Valve (Tube, Thermatron) in WWII

Thanks to Rogier PA1ZZ for sending us this. 

Grayson Evans KJ7UM Interview at Four Days in May at the Dayton Hamvention 2025

 

LISTEN TO THE INTERVIEW HERE: 

http://soldersmoke.com/KJ7UM at Dayton 2025.mp3

Grayson said quite a lot in this short 4 minute interview: 

-- At FDIM he was selling his wonderful book "Hollow State Design for the Radio Amateur."  Buy one here: https://www.ermag.com/product-category/books/ 

-- Grayson was also selling a Thermatron version of our beloved Michigan Mighty Mite transmitter.  It is crystal controlled for the 40 meter band, but the Color Burst Liberation Army approves! Here is a wonderful video on this rig:

https://soldersmoke.blogspot.com/2024/09/excellent-new-video-from-grayson-kj7um.html

And be sure to watch Grayson's excellent course on Thermatron Homebrewing: 

https://soldersmoke.blogspot.com/2024/02/grayson-evans-kj7um-video-on.html

-- Asked why someone should build with tubes when so much good solid state stuff is available, Grayson makes some especially excellent points:  The solid state gear is often filled with mysterious little black boxes -- we often don't really know what goes on in there.  Thermatron construction provides a break from complicated SDR nonsense "that is not really radio."  That last comment will generate some criticism, but not from here.  I think Grayson is right,  He earlier expressed admiration for complex circuitry, but he also rightly defends simple, understandable rigs.  

Here are Grayson's Technical Documents (a real treasure trove):  https://kj7um.wordpress.com/

Three cheers for Grayson.  And thanks to Bob Crane W8SX for doing this interview.  

The Copasteic Flow Blog -- German UHF Mobile CW Through a Geostationary Satellite, Agent Sonya's Homebrewing, More

It is always good to be reminded that someone out there is listening and reading,  especially when it is nice folks like Hamilton and his family. These are the people who built the TouCans rig that was (is?) suspended above San Francisco at the center of a dipole antenna.  

Following posts on the SolderSmoke blog, Hamilton has been monitoring the CW activites of a German ham who sends UHF CW signals through the sunroof of his car to the QO-100 satellite in geostationary orbit.  See above.  Very cool.  Listen live to the satellite here: 

https://eshail.batc.org.uk/nb/

Also cool is Hamilton's analysis of Agent Sonya's ability to homebrew a 1930s era CW station that could be used to communiate with Moscow Center.  Hamilton believes she could do it.  I have my doubts.  But the discussion is a lot of fun. 

Check our their blog: 

https://copaseticflow.blogspot.com/

Thanks to Hamilton and his kids! 

"Seems Like Radio is Here to Stay" -- Old Radio, Radio Magic

The first 12 minutes of this podcast are pretty good.  I think it captures well the wonder of radio -- magic carpets, signals taversing the Himalayas and all that -- but the presentation is kind of confused.  The PRX podcasters keep saying that it was recorded in the 1930s, but then we hear references to the Nuremburg trials and the possibility of sharing the atom bomb. So there is some confusion in the presentation. 

https://podcasts.apple.com/us/podcast/champions-of-old-radio/id453044527?i=1000702716017 

Can anyone find the original recording from the 1930s about the wonder of radio, without the references to things that happened in the late 1940s? 

Thanks to Rogier for sending this to me. 

Norman Corwin

Victor's FB SolderSmoke Direct Conversion Receiver from Holland Pulls In Stations from All Over Europe... and One from Japan

Victor is a retired Electrical Engineer from the Netherlands.  He doesn't have a ham radio call sign, but as I have said about other receiver builders, he deserves one.   Note the truly homebrew approach that Victor used on the PTO coil form.  And he had to rebuild this part to get the receiver on 40 meters.  As we can see in the above video, Victor's homebrew receiver is pulling in stations from across Europe.  Victor even reports hearing a Japanese station.  FB! 

Victor writes:

Hi Bill, I changed the PTO tuning unit, more stable this way.   I m a retired electrical engineer, revamping on a more daily basis  tube radios from the 50's 😉 I include a Bluetooth interface too so they can be used again by "young" people with their smartphones..  I had great fun and learning experiences building the DCR !!  

Thanks for the video, pictures, and messages Victor.  Congratulations! 

For more information on how you too can build the receiver: 

Join the discussion - SolderSmoke Discord Server:

https://discord.gg/Fu6B7yGxx2

 

Documentation on Hackaday:

https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver

 

SolderSmoke YouTube channel:

https://www.youtube.com/@soldersmoke