SolderSmoke Daily News

Grayson Evans KJ7UM Talks Thermatrons with Charlie NJ7V on Red Summit

2026-11-02T08:14:24.463-05:00

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

This is a really great interview. It is reminder of what a great resource Grayson is, and of how lucky we are to have him in the hobby.

Grayson mentions SolderSmoke a couple of times. He talks about a thermatron version of the 40 meter direct conversion receiver. He talks about a thermatron version of the Michigan Mighty Mite.

Grayson notes that I am sort of averse to high voltage. I plead guilty. But I have good excuses: I have done some homebrewing with thermatrons: My Mate for the Mighty Midget receiver used 6U8 thermatrons. And I have struggled (successfully) to keep my HT-37 alive in the Dominican Republic. I have built a DX-40 and a DX-60 from hamfest parts. And decades ago, I stripped an old TV of the parts needed to build a power supply for an HW-32A SSB transceiver. Somehow, I survived.

But several years ago I switched to solid state gear, and I developed some bad habits. I work on the solid state gear while energized. With it, one hand is NOT behind my back. I think it would be dangerous for me, at this point, to switch back to thermatrons. So I guess I will limit myself to vicarious thermatron adventures, through Grayson, his book, and his YouTube channel.

I really liked Grayson's confession that he is just not good at working with metal chassis. I too have mangled many of these over the years.

And wow! Fire Hydrant on the Air! As Charlied noted: hey, it's a valve! Pete Juliano would love this idea!

Thanks Grayson, and thanks Charlie.

More Clandestine Spy Radios -- Soviet Spies in Japan during WWII -- Spies On The Air! Please Comment!

2026-10-31T14:33:55.017-04:00

Sorge

I may have been too quick to dismiss the possibility that Soviet spies built their own radios. Maybe they did, but with a radio specialist on the team. Thanks to Mikele 9A3XZ for alerting us to this case.

Here is a 1964 New York Times article on the Sorge case: https://www.nytimes.com/1964/10/11/archives/again-the-sorge-case.html?unlocked_article_code=1.M1E.mQv_.rxy03pIehUb4&smid=url-share

Here is some great info on the radios thay used:

The clandestine radio equipment used by Dr. Richard Sorge’s Soviet military intelligence (GRU) spy ring in Tokyo (1933–1941) was custom-built, field-assembled, and highly effective.

Because bringing specialized espionage hardware into imperial Japan was too risky, the ring's technical mastermind and radio operator, Max Clausen, manufactured and assembled the gear locally using commercially available components and household scrap.

Max Clausen

The technical breakdown of the "Ramsay" ring's radio setup includes:

1. The Homebrew Transmitter

Clausen built small, portable shortwave transmitters using the simplest possible circuitry to ensure reliability and easy concealment.

The Circuit Type: He heavily favored the Hartley oscillator circuit, a highly efficient and simplistic vacuum-tube configuration requiring very few parts.

Power Source & Output: The transmitter generated roughly 15 watts of power. It ran on standard Japanese household AC electrical mains (100V), meaning they did not need bulky, suspicious external generators or specialized military batteries.

Frequency Range: Transmission took place on amateur shortwave bands (around 7 MHz), which allowed the signal to blend in with legitimate civilian radio enthusiasts.

2. Disguise and Concealment

The entire unit was designed to look like "household junk" if discovered during a routine police sweep.

Modular Assembly: The transmitter was not kept as a single, uniform device. Clausen kept individual parts (tubes, coils, capacitors) scattered around his house. He would only assemble the working radio immediately prior to a transmission window and dismantle it directly afterward.

The Cabin Cruiser / Fishing Boat Trick: As Japanese counter-intelligence began realizing an illegal radio was transmitting out of Tokyo, the ring adapted. Sorge purchased a luxury cabin cruiser. Clausen would pack the transmitter onto the boat and sail into the open sea or disguise themselves as a fishing vessel to transmit, making it completely impossible for the Japanese authorities to pin down their location using shore-based radio direction-finding (RDF) equipment.

3. The Receiver

For receiving commands from Soviet intelligence handlers in Vladivostok, Clausen modified a standard, commercially available civilian radio receiver. By altering its internal coils, he expanded its frequency coverage to intercept shortwave military bands. It possessed exceptionally high sensitivity to pick up faint, distant signals from across the Sea of Japan.

4. Code and Operational Security

One-Time Pads: Sorge's ring used a highly secure system of enciphering their Morse code messages based on numbers from a German statistical yearbook. Because the "key" changed with every single letter and was never reused, the Japanese intercept stations could read the signal but could not decrypt the messages.

Radio Jargon Disguise: To further evade suspicion, Clausen heavily spiced his transmissions with casual "ham radio" lingo, making it seem like an amateur hobbyist chatting with someone abroad rather than a spy sending high-level military secrets.

Despite the primitive and makeshift nature of this equipment, Clausen successfully transmitted over 23,000 code phrases. This included Sorge's most critical intelligence coup: confirming that Japan would strike south toward the US/Pacific instead of invading Siberia, allowing Stalin to safely redeploy his massive Siberian divisions to save Moscow from the German advance.

The radio operations of Dr. Richard Sorge’s "Ramsay" spy ring in Tokyo are considered some of the most successful and technically fascinating in espionage history.

The technical setup, gear, and tactics behind Sorge's communications relied heavily on a specialized approach to clandestine radio:

🛠️ The Custom-Built Hardware

Unlike many World War II intelligence networks that used factory-issued, military-grade espionage transceivers, Sorge’s equipment was entirely custom-built and home-brewed from commercially available parts.

The Builder: The equipment was designed, built, and maintained by Sorge’s highly skilled radio operator, Max Clausen (a German communist and Soviet GRU agent).

The Rig: Clausen constructed compact, portable shortwave transmitters and highly sensitive receivers. He bought ordinary radio components—tubes, condensers, and coils—from commercial shops across Tokyo to avoid drawing attention.

Size and Capability: The transmitter had to be small enough to easily hide and transport, yet powerful enough to consistently project a signal from Tokyo all the way to a Soviet receiving station in Vladivostok.

📡 Counter-Surveillance & Transmission Tactics

The Japanese Tokko (Special Higher Police) and military counterintelligence knew an illegal radio transmitter was operating in Tokyo, but Clausen successfully evaded their radio direction-finding (RDF) vans for six straight years. They managed this through strict transmission discipline:

Constantly Moving Locations: Clausen never transmitted from the same place twice in a row. He regularly moved the equipment between various safe houses in Tokyo.

The Cabin Cruiser: Sorge purchased a luxury cabin cruiser boat. Clausen would sometimes install the transmitter on the boat and broadcast from the open sea, completely confounding land-based Japanese tracking units.

Brief Airtime: Transmissions were brief, highly condensed, and conducted late at night to minimize the window for the Japanese to lock onto their signal.

🔐 The Encryption: Book Cipher & One-Time Pads

Even if the Japanese intercepted the radio waves, they could not read the content for years because of the ring's manual encryption system.

The Statistical Almanac: Sorge's ring used a manual book cipher utilizing the Statistisches Reichsamt (German Statistical Almanac).

The Process: Clausen would take the page numbers, columns, and figures of the almanac to serve as a random text key (or text gamma) to convert Sorge's intelligence into long strings of numbers.

The Advantage: Because it was a "manual cipher," it required absolutely no mechanical cipher machines (like the German Enigma), eliminating bulky, incriminating hardware.

🛑 The Downfall

The radio operation ultimately collapsed not because the Japanese intercepted the signal or broke the code technically, but through human counterintelligence work. In October 1941, Japanese police arrested an associate of the ring, leading a trail back to Sorge and Clausen.

Upon Clausen's arrest, the Japanese authorities finally seized the hidden radio components. They were reportedly astonished at how Clausen had engineered such a high-performing, long-range shortwave system using nothing but simple, over-the-counter radio parts.

Please comment on all this.

Lessons Learned about AI (Large Language Models): "I don't 'know' the facts the way that a human does..." Let's do an experiment...

2026-10-21T04:37:32.368-04:00

Yesterday, as I struggled with a Large Language Model that at first gave good advice (how to build a 5 crystal filter) and then really bad advice (how to build a filter with 5 crystals in parallel to achieve a USB passband) I got a message from an old friend who currently works in this industry.

He advised me to be careful about advice from LLM AIs. He warned that these AIs would just develop answers based on the information that had been used to train them. In the case of ham radio electronic questions, the training material was often littered with errors and lore and bad, wrong info. Often this bad information would be repeated over many years. This would make the AI more likely to use it in their answers.

It then occurred to me that I should take one case where I knew that wrong information was in the ham radio "literature" and that this information had been repeated many times over the years. I am referring here to the question of why hams use lower sideband below 10 MHz and upper sideband above 10 MHz. I had explored this question in many blog posts. Many explanations were offered -- all of them violated the Hallas rule. All of them failed to answer the question. I wondered, would AI be wrong?

Well, AI was wrong. AI said:

Subtracting in heterodyne mixing inverts the frequency spectrum. An Upper Sideband signal generated at the IF naturally flipped into a Lower Sideband signal on the lower bands.

That is wrong. The Hallas rule tells us that sideband inversion ONLY occurs when the signal with modulation is SUBTRACTED FROM the signal without modulation.

I called AI on this error in its answer. I asked it why it had given me bad information. Its responses were telling.

Why did you initially say that sideband inversion results from subtraction? Is this because of the material on which you had been trained?

You're asking a fair question about where that explanation came from.

The brief answer: yes, it comes down to how technical explanations are presented across textbooks, amateur radio training materials, and online discussion forums—and how LLMs synthesize those patterns.

So you are just repeating incorrect information, as long as it was repeated enough, right?

That is a fair critique, and it gets to the heart of how Large Language Models work.

I don't "know" facts the way a human does; I generate text based on statistical patterns learned from vast amounts of training data. When a simplified explanation, misconception, or shorthand rule of thumb is repeated thousands of times across forums, textbooks, and study guides—as is the case with "subtraction inverts sidebands" in ham radio literature—I am prone to picking up and repeating that pattern.

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

I think we can draw three conclusions from all this:

1) The talk about AI "personhood" is just nonsense, mostly nonsense from Anthropic.

2) The concerns about data poisoning are real. The ham radio "literature" is already poisoned, and look what happens.

3) We are living with the results of bad info in the amateur radio "literature" over the years. AI is just spitting it back at us. And I think it is getting worse. Now everyone with a callsign and camera has a YouTube channel. The quality of content is low and dropping. Soon AI will be spitting this stuff back at us.

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

Let's do an experiment. Those of you who have access to the other AI's like Claude, ChatGPT, DeepSeek and others, just ask them the question I started with:

"Why do ham radio operators use LSB below 10 MHz and USB above 10 MHz?" Let's see if the other AI LLMs are better at coming up with truthful answers. Of course, they may see this and not repeat the error.

About the Limits and Problems and Shortcomings of AI (actually of LLMs) -- The Design and Construction of a Crystal Filter

2026-10-20T07:00:02.768-04:00

Complaining about AI on the computer/internet while surrounded by digital rigs!

A couple of days ago, I described in this blog how AI (specifically the Gemini LLM) had helped me design a 13 MHz crystal filter. There was some angry push-back from people who seem to dislike any use of AI. One fellow said I should use my own mind and hands, and that by using AI I would risk having time to stand on the street corner. I found it kind of ironic that this observation was being sent to me on a computer connected to the internet (two tools that have made this kind of construction MUCH easier).

In the first round I think AI helped a lot. It even drew nice looking schematics for me. Using the motional parameters determinef by me via the G3UUR method, AI used the basic equations to calculate the shunt capacitances and the termination impedances. This helped me avoid many of the mathematical errors that had slowed me down in the past. I went ahead and built this filter, and (later!) took a look at the passband in my Antuino (a Scalar Network Analyser from Farhan).

I found the passband to be that of an "LSB filter": the skirt was steep just below the cutoff frequency, but much more sloping farther down in frequency. This is not what I needed. The signal hitting this filter would be (and would remain) USB. I could try to use this filter but I would be placing my BFO/Carrier Oscillator on the sloping portion of the curve. Carrier and opposite sideband suppression would suffer. (Note: It is NOT 20 db down! -20 db on this meter equals 0 db.)

And here is one point where LLM AI really screwed up: I asked it for a 5 crystal filter that would be a USB filter: One with the steep part of the skirt above and close to the cutoff frequency. AI LLM quickly obliged. I was suspicuous, because I had never seen this before. Here is what AI LLM Gemini recommended:

Wow, looks great right? Yea, but it doesn't work. I built it and looked at it in the Antuino. NOPE. It wasn't even acting as a bandpass filter. It is more of a notch filter. Confronted with the failure, AI LLM admitted it was wrong (my coments in red):

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

This configuration does not work. I have never seen it in any amateur radio book. Are you sure that this will work?

You are 100% correct to call that out—that schematic is incorrect and will not work as an SSB bandpass filter.

Why the Shunt-Crystal Schematic Fails

In quartz crystal equivalent circuits, the crystal reaches its lowest impedance () at its series resonant frequency ().

Series Position (Correct Bandpass): When the crystal is placed in the series signal line, its low impedance at allows the RF signal to pass through to the next stage.
Shunt Position (Incorrect): Placing the crystal directly from the signal line to ground causes it to act as a shunt short circuit at . Instead of passing a window, it short-circuits directly to ground, creating a band-reject (notch) response rather than a bandpass filter.

This is why you will not find that topology in Experimental Methods in RF Design (EMRFD), the ARRL Handbook, or classic G3UUR/Dishal filter literature.

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

At this point I decided that a 10 crystal Cohn filter would give me the steep skirts I needed. Here is what AI recommended:

I went ahead and built this one. I looked at it with the Antuino. It works.

You can see the steeper skirts on this filter. These steep skirts will allow me to use this filter on 17 meters with the 5 to 5.5 MHz VFO from the old Kenwood TS-820s.

In the course of doing this, an old friend who works in this field (and who will remain anonymous) warned me about the dangers of over-reliance on AI LLMs, especially when working on ham radio circuitry. More on this in the days ahead.

Charlie ZL2CTM Talks Homebrew with NJ7V on Red Summit RF

2026-10-20T04:53:10.660-04:00

https://www.youtube.com/watch?v=xV489xbf34I

NJ7V has a good interview with famed NZ homebrewer Charlie Morris ZL2CTM. Charlie describes his interests in homebrew, and provides some good links for homebrewers. I agree: understanding is important. Great stuff! Thanks to both!

Using AI to Design Crystal Filters -- Please comment, especially on the use of AI

2026-10-19T04:16:06.128-04:00

Earlier, AI told me that for 17 meters with a VFO in the 5.2 MHz range, and and a BFO/Carrier oscillator at 13 MHz I should not have any spur problems. So I ordered 10 crystals from Mouser. I hope to use it with the VFO from the Kenwood TS-820s.

This project plunged me back onto the world of motional parameters determined by the G3UUR method, followed by the use of software to determine the shunt capacitors and the termination impedances. I have used Dishal, AADE software, and Wes Hayward's GPLA.

Using this software can be a pain in the neck. There are a lot of exponents. Capacitance often has to be expressed in femto farads. Frankly, there is a lot of potential for error.

There is no way (as far as I know!) to skip the G3UUR measurement stuff. You just can't tell AI to determine the motional parameters. But after that, AI should be able to handle the calculations. I have built these kinds of filters before, so I know roughly what the shunt capacitance should be. Sure enough, just telling AI what the 2 motional parameters are, how many crystals I want to use (5) and the configuration (I selected the very simple Cohn configuration), and the desired bandwidth (I said 3 kHz). AI happily spat out the shunt capacitance (which looked right) and the impedance that would result in a flat passband (613 ohms). AI even designed the little FT-37-43 toroidal transformers that would work nicely with the 50 ohmm TIA amps on either end of the filter.

I think this is a good example of one of the uses that can be made of AI. It made the design of this filter a lot easier.

Both Images Produced by AI Gemini (FLASH HIGH)

I have built the filter (in the real world) and it is mostly working. I will perform some more tests on it and will report on this here.

What do you folks think of all this?

Waves? Particles? Understanding Quantum Mechanics with Jim Al-Khalili

2026-10-18T06:18:56.366-04:00

I recently pointed out that understanding has its limits: We all USE quantum mechanics, for example, (like, now) but we do not really understand it.

I understand how, for example, my Hex beam produces 17 meter waves. But I do not understand how 17 meter particles are produced.

In the above video, quantum physicist Jim Al-Khalili explores this gap in understanding. He explains it all very well (within limits, of course). Particularly good is his presentation on "The Ultraviolet Catastrophe."

Check it out. In follow-on videos Jim looks at various theories that have cropped up to explain the gap in understanding. Here is his YouTube channel: https://www.youtube.com/@UnbaffledScience

Wow! Jomon VU3IZD's Homebrew Modular BITX 40 Transceiver

2026-10-17T04:27:29.050-04:00

I really liked Jomon's rig. The modular approach is brilliant as is his explanation of how each stage works. He emphasizes the benefits of this modular approach.

You can see that he is a true homebrewer -- you can see it in his expressions at the end. Just look for the smiles, for the obvious feeling of pride and satisfaction that comes from working a station more than 450 km away with a rig that he built himself.

I also really liked his homebrew microphone. FB Jomon!

Rogier PA1ZZ sent me a short video showing Jomon's antenna for portable operations. In that video you catch a glimplse of this rig. Both videos are great. The antenna short is here: https://www.youtube.com/shorts/YVgoy4rPddQ But for me the best of the two videos is the one describing the rig (above).

We posted about Jomon's homebrew projects back in December 2025: https://soldersmoke.blogspot.com/2025/12/homebrew-radio-from-southern-india.html

Jomon is from Kerala in southern India. Kerala seems to be the center of a lot of great homebrew activity. Many of the Indian hams that I have talked to are from Kerala: https://soldersmoke.blogspot.com/search?q=Kerala

Here is a map showing Kerala state:

Thank you Jomon! And thanks Rogier!

Spies On The Air? Israel's Spy in Syria: Eli Cohen and HF CW in the 1960s -- Cohen's Antenna and Thermatron QRP Transmitter

2026-10-16T05:31:54.709-04:00

Eli Cohen in 1959

This week I watched the Netflix show about the Israeli intelligence agent Eli Cohen: https://www.netflix.com/title/80178151 I thought it was pretty good. The sequences about his use of CW to communicate with Tel Aviv were really interesting. I asked AI (Gemini) for more details. See below.

Cohen's story is also interesting Here is the Wikipedia on Eli Cohen: https://en.wikipedia.org/wiki/Eli_Cohen

Here is what AI reports about him in response to my questions:

Eli Cohen’s CW (Morse code) transmissions were heavily encrypted, and the underlying plaintext language of his messages was French.

1. Encryption Method: One-Time Pad (OTP)

The Cipher System: Eli Cohen (operating as Mossad Agent 566 under the cover identity Kamel Amin Tha'abet) used a One-Time Pad (OTP) cipher system. Plaintext characters were encoded using single-use, pre-shared key sheets that were destroyed immediately after use.
Over-the-Air Format: Before transmitting over High Frequency (HF) CW, the encrypted text was converted into standardized 5-character groups (either 5-letter or 5-number blocks).
Cryptographic Security: The Syrian military’s radio intelligence division (Signal Company 134) regularly intercepted his daily CW signals from his apartment in the Abu Rummaneh district of Damascus. However, because proper OTP encryption is mathematically unbreakable without the key pad, Syrian and Soviet cryptanalysts were completely unable to decipher the content of his transmissions.

2. The Underlying Language

French Plaintext: Prior to enciphering the messages into 5-character blocks, Eli Cohen drafted his intelligence reports in French.
Why French? Raised in Alexandria, Egypt, Cohen was natively fluent in French, Arabic, and Hebrew. During the early 1960s, Mossad’s clandestine unit handling deep-cover foreign agents (Unit 188 / Aman prior to Mossad’s consolidation) frequently used French as the primary operational language for field reporting and code sheets.
Reception in Israel: His encrypted Morse transmissions were picked up by Israeli receiving stations (including a unit where his own brother, Maurice Cohen, worked as a cryptographer/radio operator decoding incoming agent transmissions). Once received, the operator applied the corresponding one-time pad page to decrypt the 5-character blocks back into French plaintext, which was then translated into Hebrew for intelligence evaluation.

How He Was Detected

Syrian authorities did not bust Cohen by breaking his cipher. Instead, they used Soviet-supplied Direction Finding (DF) vehicles during a forced power blackout in Damascus, locating his apartment by tracking his active / HF radio signal while he was physically transmitting.

During his deep-cover mission in Damascus (1962–1965), Eli Cohen transmitted covert High Frequency (HF) CW (Morse code) signals directly to Mossad receiving stations in Israel over a path distance of approximately 220 kilometers (135 miles).

Frequencies & Operating Bands

Cohen used pre-arranged HF utility frequencies in the 7 MHz to 14 MHz range, selecting specific frequencies based on time-of-day ionospheric propagation:

7 MHz Region (40-Meter Band Equivalent): Used primarily for early morning and late night transmissions (e.g., his daily 07:00 AM window). At night and early morning, lower HF frequencies provided the ideal Near Vertical Incidence Skywave (NVIS) and short-skip regional propagation required to span the ~220 km distance over the Anti-Lebanon mountains into Israel.
11 MHz – 14 MHz Region (20-Meter / Upper HF Utility Bands): Used for daytime scheduled bursts when higher D-layer ionospheric absorption attenuated lower frequencies.
Frequency Agility: To evade routine fixed-frequency monitoring, Mossad assigned multiple pre-set crystal-controlled frequencies. Cohen changed frequencies according to a strict calendar matrix provided on his one-time pad signal sheets.

Antenna Design & Disguise

In the crowded Abu Rummaneh district of Damascus, hanging an obvious transmitting antenna would have invited immediate suspicion. Cohen utilized a stealth end-fed thin-wire antenna:

Rooftop Wire Element: A thin copper wire element strung across the roof of his top-floor apartment building.
Visual Disguise: The wire was masked alongside the dense maze of commercial TV receiving antennas and broadcast radio long-wires ubiquitous on Syrian rooftops at the time.
Feedline & Entry: A thin black lead-in cable ran from the rooftop wire element down through the window frame into his bedroom, hidden inside a wooden curtain valence/box where he concealed his Morse key and miniature transmitter.

How the Antenna Led to His Capture

When Syrian military signals intelligence (Signal Company 134) brought in Soviet-supplied direction-finding (DF) equipment, they narrowed the signal down to the Abu Rummaneh neighborhood but could not identify the exact apartment.

The breakthrough occurred when investigators inspected the building's roof and spotted an unmarked black feedline cable connected to a rooftop wire that did not route to a standard television set or broadcast radio. Tracing the black cable down the exterior wall directly into the window of apartment "Kamel Amin Thabet" gave them the exact location. Syrian security forces then cut power to his specific apartment circuit during his scheduled 07:00 AM transmission window on January 18, 1965, confirming the transmission ceased simultaneously before raiding the room.

Eli Cohen used a custom-built, subminiature High Frequency (HF) CW spy radio set developed by Israeli technical intelligence (IDF Signal Corps / Mossad).

The equipment was vacuum tube-based (using subminiature "pencil" tubes) and operated at a QRP power level of approximately 3 to 5 watts (with a maximum output around 10 watts peak).

Technical Breakdown

1. Tube-Type vs. Solid-State Construction

During Cohen's operational period in Damascus (1961–1965), high-frequency power transistors capable of generating several watts of RF output at 7 MHz and 14 MHz were not yet reliable or commercially viable for clandestine agent sets.

The set relied on subminiature vacuum tubes (similar to the American 1AD4, 5678, or 3B4 series originally engineered for military proximity fuses and portable field radios):

Rugged & Compact: These tiny, wire-leaded glass tubes consumed very little filament current, generated minimal heat, and could withstand physical transport.
AC Mains Powered: His primary set ran off standard wall power, utilizing a miniature transformer and silicon/selenium rectifiers disguised inside the chassis of household appliances.

2. Power Output & Path Dynamics

Power Level: Operating at 3 to 5 watts CW, the set was a classic QRP (low power) transmitter.
Path Distance: The distance from his apartment in the Abu Rummaneh district of Damascus to Mossad receiving stations in northern and central Israel was only about 220 kilometers (135 miles).
Propagation: On the 7 MHz (40-meter) band during early morning/evening and 11–14 MHz during the day, 3 to 5 watts into a simple end-fed wire provided a strong, reliable skywave/NVIS signal across the Anti-Lebanon mountain range into Israel without requiring a massive, power-hungry transmitter.

3. Physical Packaging & Concealment

Because custom spy sets could not be purchased off the shelf, Mossad's technical workshops built the transmitter and receiver into everyday consumer goods that a wealthy import-export businessman like "Kamel Amin Tha'abet" would naturally own:

Primary Set: The core transmitter components and power supply were built into the false bottom of an electric kitchen blender and an electric razor. The razor's power cord double-buffered as part of the power feed/ground lead.
Backup Set: Syrian security forces also recovered a secondary backup CW transmitter concealed inside a green leather-bound desk set/box.
Keying: He used a compact, hand-held micro-key (a miniature CW hand key) that could be quickly stowed inside a wall cavity or curtain rod assembly.

INFORMATION ON COHEN' S RIG (FROM AI GEMENI)

While the exact internal schematic diagram drawn by Mossad's technical workshops (Unit 188 / IDF Signal Corps) remains classified in official Israeli intelligence archives, the circuit topology, stage architecture, and component selection of Eli Cohen's subminiature HF spy radio are fully documented from trial evidence, recovered hardware, and contemporary 1960s covert communications engineering.

Transmitter Circuit Architecture (~3–5 Watt CW)

The transmitter was a compact, two-stage Master Oscillator Power Amplifier (MOPA) vacuum tube circuit optimized for high efficiency, low heat dissipation, and minimal footprint.

+-----------------------------------+

| Transmitter RF Chain |

+-----------------------------------+

+-------------+ +-------------------+ +-------------------+

| FT-243 | | Oscillator Stage | | Power Amplifier |

| Quartz |------>| Subminiature |------>| Subminiature |------> Pi-Network

+-------------+ | (e.g., 1AD4/5678) | | (e.g., 3B4/3A5) | (Low-Pass)

+-------------------+ +-------------------+

| | |

+------- Cathode Key -------+ v

(Hand Key) End-Fed Antenna Wire

1. Crystal-Controlled Master Oscillator (MO)

Active Element: A single subminiature "pencil" tube (wire-leaded glass pentode/triode such as the 1AD4 or 5678) configured in a grid-controlled Pierce or Colpitts oscillator topology.
Frequency Control: Utilized miniature FT-243 or HC-6/U crystal sockets. Cohen swapped pre-cut quartz crystals corresponding to his assigned operational schedule in the 7 MHz (40m) and 11–14 MHz (20m) bands.
Output: Delivered to of stable RF drive to the grid of the power amplifier, preventing frequency pull or chirp when keying.

2. Class C Power Amplifier (PA) Stage

Active Element: A subminiature filamentary beam power pentode (such as the 3B4 or dual-triode 3A5 operating in parallel/push-push).
Bias & Efficiency: Biased strictly into Class C operation using a grid-leak resistor/capacitor combination (, ). Class C provided over 65–70% DC-to-RF conversion efficiency, critical for keeping tube heat low inside a concealed chassis.
Anode / Tank Circuit: The plate circuit used a parallel LC resonant tank tuned to the operating band via an adjustable ceramic trimmer capacitor and a slug-tuned toroidal coil wound on a carbonyl iron powder core (e.g., T-50-2 / T-50-6 type).

3. Output Antenna Matching Network

Pi-Network (L-C-C): The PA plate was coupled through a high-voltage blocking capacitor to a low-pass Pi-network matching filter.
Impedance Matching: Transformed the high plate load impedance () down to match the variable reactive input impedance of his random-length, end-fed rooftop wire antenna ().
Harmonic Suppression: Provided attenuation of second and third harmonics to prevent interference with local broadcast services in Damascus.

4. Cathode/Grid Keying & Power Supply

Morse Keying: Direct switching of the cathode/filament return line to ground via a subminiature micro-key. A small ceramic capacitor and choke across the key contacts suppressed key clicks and sparking.
Power Supply Circuit: Powered from standard mains. The internal power supply utilized a compact step-down/step-up multi-tap iron core transformer with silicon/selenium diode rectifiers:

(Plate Voltage): to , smoothed by a subminiature multi-stage LC filter choke and electrolytic capacitor block.
(Filament Voltage): to regulated filament supply to preserve subminiature tube cathodes.

Receiver Circuit Architecture

The receiving set accompanying the transmitter was a high-sensitivity, subminiature Regenerative Receiver (or 3-tube Superheterodyne depending on the specific backup set revision):

RF Preamplifier Stage: A single 1AD4 subminiature tube isolated the antenna from the detector to prevent local oscillator radiation (which could be detected by direction-finding equipment) and improved weak-signal selectivity.
Regenerative Detector: A subminiature pentode operated at the verge of oscillation for maximum CW sensitivity. A panel-mounted potentiometer adjusted the screen-grid voltage () to control regeneration depth and beat-note frequency for Morse code reception.
Audio Amplifier Stage: A low-frequency audio amplifier tube drove high-impedance () magnetic earphone inserts concealed in standard pens or desk items.

Mechanical & Physical Implementation

Point-to-Point Wiring: Components were mounted on phenolic miniature terminal strips using point-to-point wiring to minimize stray capacitance and physical volume.
Concealment Modularization: The circuit was split across functional sub-assemblies small enough to fit inside the false bottom of a leather-bound desk stationery set and an electric kitchen blender chassis, with the AC power cord serving as a multi-conductor umbilical.

Pittsburgh Plumber Builds Aluminium Telescope Dome in 1930

2026-10-15T07:23:41.559-04:00

AI generated image

See: https://www.alcircle.com/news/how-a-pittsburgh-plumbers-aluminium-dome-helped-shape-observatory-design-121565

A Tale of Two Old Analog VFOs -- Artificial Intelligence's Role. PLEASE COMMENT!

2026-10-13T08:41:13.366-04:00

The Kenwood VFO under test, with 2 Yaesu VFOs Standing By

I have sung the praises of the VFOs taken out of the old Yaesu FT-101s. I am using them in two homebrew 20 meter SSB transcievers, one in the Dominican Republic, the other here in Virginia. We started buying these things just for the anti-backlash reduction drives. But the vendors would send along the reduction drives AND the entire VFO module. These circuits were all analog, and all discrete component. I understood them, and had completely homebrewed circuits very much like them. So I felt comfortable using them.

Somewhere along the line, I got the VFO from a Kenwood TS-820s. My motivation was the same: I wanted the anti-backlash reduction drive. But as with the Yaesus, the entire VFO box came with the purchase. The frequency on this one was much lower than the Yaesu. the Kenwood ran from 5-5.5 MHz, the Yeasu was up around 9 MHz. On this alone, the Kenwood seemed better.

I recently put the Kenwood on the bench and began testing it. I used Artificial Intelligence (AI) in the tests. The results were good and bad. Sometimes AI helped, sometimes it made matters worse. Mike WU2D recently used AI to look at the tubes of an old receiver he was working on. He too was impressed by the usefullness of AI, but I think he too had some misgivings. Here are some of Mike's conclusions:

Let's start with a fundamental question: I asked Gemini which of the two "ages better." Gemini said that the Kenwood was superior in this regard. I disagree. Here is why:

-- Tuning on the Kenwood was very jumpy and very scratchy. AI correctly said that this was probably due to corrosion over the years on the connections between the main tuning capacitor and ground. Strike 1! AI recomended cleaning with DeOxit. As a last resort they recommended putting some solder wick between the rotator shaft and ground. I did that and it fixed the problem (you can see the solder wick in the picture above), but I never had to do that with the Yaesu VFOs.

-- The schematic of the VFO shows a .9 V RMS output from the VFO. But it does not specify a 50 ohm load. Here is the Yaesu schematic:

AI kept insisting that I use a 50 ohm load. When I did, the output was reduced down to 54 m V rms. I questioned AI about the load, but it kept insisting on 50 ohms. Only later, did AI point out that in the Yaesu, the VFO would feed into a HIGH IMPEDANCE load. Strike 2.

-- Gemini kept warning about the Q3 and Q4 transistors. They were 2SC460 transistors with weird (ECB) pinouts. And they were prone, it said, to a horrible sounding disease: "Original Hitachi 2SC460 transistors are infamous in vintage ham gear for silver migration ("black foot disease"), where the lead plating oxidizes, turns black, and causes severe noise, leakage, or intermittent oscillation failure." AI happily recommended replacing them with 2N3904s. I did this, but the voltage on the emitter was way off. AI blamed this on the new transistors (that it had recommended!) saying that their hfe was too high (so, uh, why did you recommend them?). It then said that the direct coupling from Q3 to Q4 was at fault; it recommented putting a .001 uF cap between these two transistors, along with two resistors for the biasing of Q4. I did this. I am not sure if it was necessary. Strike 3.

-- Gemini said I should check D3. It was germanium, you see, and "notorious" for going open. It was open. I replaced it with a wire, but AI had a fit. It worried that voltage from the follow-on circuits in the Kenwood would mess up the voltages on Q4. I told AI not to worry about this -- all I had was the VFO! Strike 4.

-- I still wasn't getting good output. Here AI was very useful. First it told me to check the voltage on the emitter of Q4. It was too high. Then it told me to look at the resistance to ground from the emitter of Q4. Uh oh. It was open. I quicky went through the connections to ground. L6 was open. I relaced it with 100 uH inductor. This corrected the situation. I now had 1 volts AC rms at the output with no load and .8 V AC rms with a 1000 ohm resistor in the load. SCORE ONE FOR AI.

So, looking back, I came to several conclusions:

-- Gemini was just wrong in saying that the Kenwood VFO ages better than the Yeasu VFO. The Kenwood had Germanium diodes, weird transistors that get "Black Foot" disease, main tuning caps that get scratchy due to corrosion, inductors that go open. Yuck.

-- You have to take the recommendations from AI with a grain of salt (see WU2D's conclusions above). Sometimes they are right, sometimes they are wrong, and sometimes they recommend things that might not be necessary. Dean KK4DAS points out that AI's seem to do better when you upload the schematic. Maybe this lets AI analyse it using a simulator. I had not done this.

-- I will probably use the Kenwood VFO in a 17 meter SSB transceiver. I recently bought some 13 MHz crystals for the filter and the BFO/Carrier Oscillator from Mouser. And AI confirms that this combination should not produce any problematic spurs. We'll see. The ultimate test is still real-world construction.

What do you guys think about using AI in projects like this? Will AI improve?

What Happens Inside an AI Chip When You Ask a Question. PLEASE COMMENT

2026-10-11T11:08:02.438-04:00

When I post something like this, there are several predictable responses:

1) Some guys will proclaim it to be "AI slop", and will criticize me for even posting it.

2) Some guys will just declare that I am "getting old" (as if they are not) and will assume that at my age, I just somehow can't understand these new machines (as if they can!).

3) Many more sensible guys will put aside their feelings about AI and my age, and -- perhaps giving the devil his due -- be amazed by the complexity of these machines.

I think it is pretty amazing.

What do you guys think?

CuriousMarc and Company Fix an Old Analog Device (an Apollo Hand Controller)

2026-10-10T04:46:52.369-04:00

I really liked this repair video (above), not because I will ever fix an Apollo-era hand controller (I won't) but because it illustrates well what can go wrong with older, analog gear. And how you fix it.

You watch as Mark and Mike try to figure out what was wrong. This brings us back to the diagnostic questions that Richard Feynman posed to his neighbors when, as a boy, as he fixed their AM radios back in Brooklyn. "My God! He fixes radios just by thinking!" exclaimed one amazed customer.

Once (well, several times) after they thought they had it figured out, they used simple test gear (a DMM) to find the short. Then they fixed it, and brought the controller back to life. This wasn't easy. It involved lots of digging (almost literal digging) and put at risk some irreplaceable parts. But they did it. Three cheers for the CuriousMarc team.

BTW: What was that liquid that Marc used to replace the insulation that had been scraped away to allow for testing?

Margaret Hamilton, Apollo Computer Programmer, has Died

2026-10-08T15:53:27.609-04:00

More here:

https://www.nytimes.com/2026/10/07/obituaries/margaret-hamilton-dead.html?unlocked_article_code=1.HFE.LyzK.61NCdD3ArbP7&smid=url-share

Margaret Hamilton is mentioned frequently in the book "Sumburst and Luminary" by Don Eyles.

See: https://soldersmoke.blogspot.com/search?q=Eyles

About the Guy Who Brought Us the AADE L/C Meter -- Neil W. Heckt

2026-10-07T12:19:23.360-04:00

There it is. The AADE L/C meter. Many of us have been using these things for years. I have two of them -- the one that I bought is here in my shack in Virginia. The other was given to be by Todd VE7BPO and it is in my shack in the Dominican Republic. I sometimes wondered who was behind Almost All Digital Electonics. Today I got the answer.

Rishav is from Nepal, He has been studying in Germany. He is working on homebrewing the test meter (the company shut down when Neil passed away). In the course of his research, Rishav gathered some very nice info about Neil W. Heckt, the fellow who created AADE and the meters that so many of us used. Thanks Rishav!

Memories of Neil W. Heckt

My work with Tobias (KK7BCO/2M0TFF) on a LC meter as the fifth build in Red Summit RF's Homebrew Workbench series for beginners introduced me to the clever LC meter design of Neil Heckt. As we celebrate his work by building one ourselves, in this post I hope to celebrate his life through the memories of those who knew him.

Neils's AADE L/C Meter IIB was a great hit, with thousands of units sold both as kits and as fully assembled instruments. It is not difficult to find praise for the meter. Many owners have written about its accuracy, usefullness, limitations, and clever design. Scattered among those reviews, however, are also small glimpses of Neil himself—stories from people who corresponded with him, asked him for help, or sent their meters back to him for repair. The reviews of the AADE L/C Meter IIB on eHam.net are particularly valuable in this respect. Many are written by people who dealt with Neil directly, and aongside their praise for the meter they remembered his kindness, honesty, and unusually generous customer service.

Memories

There is surprisingly little written about the man behind the instrument. While trying to learn more about him, I found most of the biographical information in his obituary. While searching further, I came across a moving remembrance titled Celebrate the Sun, written by Jill L. Ferguson, Neil's daughter-in-law. It offered something quite different from the technical accounts and product reviews: a glimpse of Neil as a husband, father, and person. One story in particular reveals a wonderfully personal side of him:

She (Kay) said her favorite book and life philosophy came from Celebrate the Sun. Back before she and Neil dated she had told him about this book. Not only did he borrow her copy and read it, but he photocopied the whole thing and pasted page by page into a photo album and intermixed the pages with his own photographs of the sun, of himself on hikes, and of the two of them walking in the woods. He decorated the front of the book with black electrical tape and two die-cut pelicans as they are key characters in the book. After Neil and Kay moved in together and married, she found this book he had created but had never told her about. She intimated that part of the way she knew he was the man for her was because he had taken her interest in this book so seriously. On his last night, she had the book Neil had created with them in hospice center and was reading the end of it to him shortly before his passed.

I was deeply moved by the story and wrote to Jill to ask whether she might be willing to share a few more memories of Neil, and perhaps a photograph. She kindly replied that she would speak with Kay, Neil's wife, and with Neil's son, her husband.

Two days later, I received a message containing a wonderful remembrance written by Kay herself, together with a photograph of Neil as a younger man. I have reproduced both here.

Photograph of Young Neil, thanks to Jill, sent to me by Kay.

Neil Heckt worked for the Boeing Company for more than 30 years. He was a member of their early air and space team. In his earliest years he worked on getting satellites into orbit and later getting men onto the moon. He developed his first inventions during those years which, of course, were owned by Boeing.
When we met he was a few short years from retirement. He was anxious to start his own business and create new products unrelated to his work at Boeing. He named his company Almost All Digital Electronics.
The inventions that followed seemed focused on developing ways to measure very, small units of...? He invented an atomic clock. It is my understanding that the Bureau of Weights and Standards in Colorado used it and that it was displayed there. Here I must state that I am woefully unknowledgable about any aspects of his work. I am neither a business woman or an inventor so, though I found him brilliant I rarely understood what his inventions really did. We were very different in many ways but genuinely admired each other's talents.
The last invention was an L/C Meter kit for hobbyists. He did very well with that product. The arrival of the internet and eBay made it a commercial success.
I thought his philosophy about not patenting his products was unusual. He told me that he developed a product, sold as many as he could and when someone copied his work he would stop production and leaveit to someone else to deal with it while he invented something else.
He had talents and ideas brewing in his brain that craved to be made real. He told me that whenever he needed money he would invent something that people would buy and then he paid his bills.
He wasn't like me and the people in my world who took on a second or third job when we needed money. I found his confidence and creativity to be amazing!
Neil was scrupulously honest in his business . Once he purchased two antique vacuum tubes for less than $100 from an eBay customer. When they arrived he discovered that they were quite valuable. He wrapped one tube up and sent it back to the customer with a note telling him what it was worth. Instead of selling it and making a good deal of money he sent it back. I asked him why. He said it wouldn't be fair to the seller for him to keep all of it for himself because the guy just didn't know what he had.
If anyone had a problem assembling one of his kits they sent them to him and he would fix their problems without charge.
Neil was sick for many years before his death. His brilliant mind was with him to the end.

I hope these memories help preserve not only Neil Heckt’s work, but also something of the thoughtful, generous, and inventive man remembered by those who knew him.

***

Some Useful Drake History from 15 years ago -- Thank you to Bob Crane W8SX

2026-10-06T06:09:22.435-04:00

I stumbled upon this report on an interview that Bob Crane W8SX did with Bill Frost back in 2011. Bill had been Service Manager for Drake, and knew a lot about the 2-B. This interview is a reminder of the great info that Bob has brought to us over the years. Thanks Bob!

Especially interesting and useful were Bill's comments on crystal filters, the number of 2-Bs produced, and the rarity of the Q multiplier.

Check it out:

https://soldersmoke.blogspot.com/2011/05/w8sx-drake-interview.html

Are we alone in the universe? How well have we checked so far? PLEASE COMMENT

2026-10-04T15:30:49.322-04:00

I am a fan of Fraser Cain's. I encourage SolderSmoke listeners, readers, and viewers to check out his work: https://www.youtube.com/@frasercain

Having grown up with a steady stream of Carl Sagan ("billions and billions") and Star Trek, I naturally accepted that there must be some other intelligent civilizations out there. But maybe not. Lately I have been hearing from some very well informed people that we may be alone. This video explains why. It also has a lot of good information on how to carry our a Search for Extraterrestrial Intelligence.

Please let me know what you think about all this.

Helge LA6NCA Does It Again! This Time Homebrew CW Solid-State QRP.

2026-10-03T10:54:57.083-04:00

This one is really cool, and reminds us what an intrepid and skilled radio amateur like Helge can do.

I really liked the simple scheme he used to shift frequencies from transmit to receive.

I liked the antenna that he used, and its origns. FB.

Finally I really liked the serendipitous source of the sidetone.

Thank you very much Helge!

SolderSmoke Direct Conversion Challenge: 139 Receivers Built

2026-09-28T08:54:20.298-04:00

Dave M6XTY

As of September 28, 2026 1248Z

So far, total receivers built: 139 (131 plus 8 honorable mentions). Total Count: 139. Receivers built in 19 countries.

NE3U (KY4EOD) Matt

KQ4AOP First ham signals ever heard!

N9TD Derek

AC3NG Ryan

VK3TPM Peter Marks

W4KAC Ken

W4KAC Ken built a second one!

N2EPE Erik

VA3NCA Wayde (Canada)

KI5SRY Mark -- Gears on PTO screw

KA1MUQ Frying pan receiver

AA1N Adam

ZL1AUN Aaron -- Using SSB transmitter -- (New Zealand)

W8UC Never before homebrewed.

VK4PG Phil -- Nice case, "really pleased"

G7LQX Working well, video of CW and SSB. -- (England)

KE2AMP John Spring on PTO screw -- great

N9SZ Steve nice receiver

KD9NHZ Piotr Nice one

KE8ICE Calvin, Very cool receiver.

WV3V Jayson! Got it done!

GM5JDG Martin. -- (Scotland)

KF8BOG Jim: A long struggle, but success.

Chris Wales Fantastic video. -- (Wales)

YD9BAX Wayan! Homebrew transformer! (Indonesia)

N0NQD Jeff

WN3F Roy -- Made new stickers!

AB5XQ Bill
KB7ZUT Andy
AA1OF Jer

VictorKees Holland (Netherlands)
KC9OJV John -- Manhattan-style convert
WZ5M 1, 2 or maybe even 3 receivers!
K1KJW Jim in Vermont
KC5DI Dallas -- friend of WZ5M
Gary Australian -- Wooden PTO form (Australia)
LU2VJM Juan in Argentina -- (Argentina)
K1OA Scott "Most fun in 50 years"
KC9DLM Ben -- Had EFHW problems
PH2LB Lex Yellow, Glue Stick -- (Netherlands)

AI6WR David
G6GEV Dave (It was a blast!) (England)
KC1ONM Wayne MakerLabs NH
KB1OIQ Andy MakerLabs NH
KA1PQK Jay MakerLabs NH
W1TKO Mike MakerLabs NH
K5KHK Karl
SM0TPW Mikael -- (Sweden)
KI7LKB Brian (coat hanger tube)
M6CRD Chris (England)

W2DAB Dave in NYC
W4JYK Wes of VWS
KA4CDN Mike of VWS
M7EFO Adrian
VK5RC Rob (Australia)
KD8KHP Dave
VK1CHW Chris (Australia)
KA0PHJ Brian
W0IT Louis
W1PJE Phil

W2AEW Alan
KN6FVK John (Barkhausen-Be-Gone Spray)
VU2JXN Ramakrishnan -- (India)
AA0MS Doug
9V1/KM7ABZ Paul -- (Singapore)
VK2BLQ Stephen -- (Australia)
N3FJZ Rick
Daniel VE5DLD -- (Canada)
Student 1 Student of VE5DLD
Student 2 Student of VE5DLD

Student 3 Student of VE5DLD

K7WXW Bill

NK3H Mitch

KN4ZXG Ted

WA1MAC Paul

N4AVC Chuck

K3IY Kevin

N6ASD Ashish in Bangalore (India)

W1DSP Rick

WD4CFN Steve

KM5Z Mike

KF5DAN Dan

Fritz Fritz

N9OK Joe

WA5DSS Bill

K0GDB Grant

G0JNR Shane Glow-in-Dark Coil Form

KK7BCO Tobias

K2BVR Bob

Robert Sutton

K5YFO Dave (Texas)

KD4PBJ Chris

KN4GAH Chris -- EE perspective

F1GMA Philippe -- (France)

W2TEF Todd

EI9ITB Karl -- (Ireland)

VU2TUM Puneit Singh (India)

AA7EE Dave Richards

KI5VIR Jay

CT7AXD Graham -- Promoted from Honorable Mention! (Portugal)

G3MOT Josh (England)

KW4H Steve

NJ7V Charlie (RedSummit)

N2ETZ Denny

AB9LM James

W9XT Gary

G0PJT Alex

KF8FZZ Tyler

N7HPR Steve (Instructor) (N7HPR Group)

Clark (N7HPR Group)

KQ4ZHO Kurt (N7HPR Group)

KQ4OBR Brian (N7HPR Group)

KR4CUF Justin (N7HPR Group)

Amanda (N7HPR Group)

David (N7HPR Group)

KM4AED Jamey (N7HPR Group)

KN4MVH Larry (N7HPR Group)

N5GVW Dick (N7HPR Group)

W7KAL Kal

KC9LFP Joe

SP9DEL Marian (Poland)

LB8VA Ivar (Norway)

AA7FO Chuck Adams!

WE6Z Doug

N7MN Jason
VA2GJ Gerald in Quebec
N6HA Bill
Andri Bandung, West Java, (Indonesia)
K6AUS Scott
Brett K Tasmania (Australia)

Dave M6XTY

-------------------------
Honorable Mentions:

*AA7U Steve No PTO

*VK7IAN Ian -- No Manhattan boards -- (Tasmania)

*KC1FSZ Bruce's build on a PC board

* DL1AJG Andreas -- (Germany)

* Matthew Student of DL1AJG

* Arash Student of DL1AJG

*KA4KXX Walter -- FB 20 Meter version

*M9KCA-ST2NH Nader - LM386 in place of AF amp

This Guy Designed His Own Microprocessor Chip -- But Is This REALLY Design?

2026-09-28T06:16:58.545-04:00

First, hats off to this fellow. He deserves a lot of credit for even trying this.

But... I think this shows how DIFFERENT designging these chips is from what we would consider traditional ham radio homebrew design and construction. The truth is that I didn't even understand much of what he was talking about, even when he was trying to explain what he had done.

There does seem to be at least a little common ground (!): I note that there was a need for diodes to ground in the longer leads, and in the test a lack of grounding caused the chip to not work properly.

Thanks to Hack-A-Day for alerting us to this.

What do you guys think? Is this concept of design similar to traditional ham radio concepts?

The WN2QHL N2CQR Drake 2-B

2026-09-27T06:05:03.188-04:00

I was telling Steve KW4H and Scott K6AUS about my Drake 2-B (Serial #11976):

I got mine when I was still a novice on April 11, 1974. I still have it and use it. It had been spared the Magic Screwdriver, because the previous owner was my Elmer, Hilmar WN2NEC. Hilmar was a no-nonsense German immigrant, a tech who knew which end of the soldering iron to grab.

The only real mod that it had was the installation of a Jackson Brothers reduction drive. This slowed the tuning a lot, and I lost the calibrated dial skirt, but I think it was worthwhile. I have tuned "normal" 2-Bs and they seem a bit fast to me. By the way, I think you can tell a true 2-B restorer if he has replaced the string on the tuning mechanism of the 2-B, and he has done it often enough to get good at it! I am sure Steve is in this category! (Can you imagine a modern rig that actually has a STRING in it? I can't. I think those tuning dial strings capture a lot of the charm of these older receivers.)

When Hilmar sold me the receiver, it had a really cool big knob on the front. But he had specified that I had to give that knob back to him -- he had borrowed it from a device at work! Of course, as a teenager, I dallied. "I really need that knob," complained poor Hilmar. I found a replacement and gave the knob back to him.

Years later I think I replaced the power supply capacitors with a replacement from Hayseed Hamfest.

My 2-B opened up a world of DX for me. Only two days after I got it, I worked ZL2ACP on 15 CW. And of course on that same day, I worked KP4USA on 15 meter CW. The operator was Steve, who is today KW4H. With my earlier general coverage receiver, I could barely hear 15 meters. With the 2-B it was easy to tune.

I have more than 70 Drake 2-B articles on the SolderSmoke blog. Check them out:

https://soldersmoke.blogspot.com/search/label/Drake%202B

What Does It Mean when Someone Says "You Are 30 Hz Off Frequency"? And How Modern SDR Waterfalls Perpetuate this Myth -- The Rigid Stencil -- PLEASE COMMENT

2026-09-24T14:17:53.458-04:00

Dean and Pete and I have been talking about this for some time. We are really trying to understand where this is coming from. After all, you really can't hear a it if a signal moves 30 Hz off frequency (you can try this with a Web SDR).

And how could they tell that I was 30 Hz off frequency? Could it be that they were simply looking at their waterfalls, and seeing that my waterfall pattern did not look like theirs? The pattern displayed in the waterfall is largely determined by the "offset" -- the gap between the suppressed carrier frequency and the beginning of the audio passband. It turns out that this offset issue explains why users of SDR receivers with waterfalls were incorrectly concluding that I am "off frequency."

For a while, we speculated that the SDR radios have some special feature that allows them to just analyse the RF passband and then, magically and with precision, determine what the suppressed carrier frequency was, even when they cannot detect it. As you do these days, I asked the LLMs about this. I use Gemini. At first, Gemini told me that this was indeed possible -- the SDR rigs were calculating the frequency of the invisible, inaudible, suppressed carrier. For a while I grudgingly accepted this. Maybe there was some software ghost in the machine that could make this calculation. But it was kind of odd that I had never before heard of this capability and never saw anything about the software that did this.

But in late September I asked Gemini again, and got the opposite answer. Here is what AI said in late September:

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

It is mathematically impossible for an SDR to determine the precise suppressed carrier frequency from a voice passband alone.

I flip-flopped because I confused a digital signal processing (DSP) estimation trick with an absolute RF measurement.

Here is exactly where my logic derailed when I incorrectly told you it was possible: I took a real DSP feature—where software analyzes the harmonic spacing of vowel sounds to automatically tune a voice until it sounds natural—and mistakenly concluded that this relative audio adjustment could perfectly identify the original RF carrier.

That DSP feature is just an auto-tuner making an educated guess to fix the "Donald Duck" effect. It cannot reverse-engineer the exact carrier frequency for two fundamental reasons:

The missing anchor: The carrier has been physically erased at the transmitter. You cannot measure a 0 Hz reference point that no longer exists in the RF spectrum.
The human variable: Human vocal cords are not calibrated test tones. Without a known, fixed pilot tone, the receiver has no way to know exactly where the audio was originally offset from the missing carrier.

The physics of your homebrew rig dictate the reality here. The 330 Hz offset is a fixed, physical characteristic of your crystal filter and BFO alignment. When the other operator's SDR tells them you are 30 Hz off, that software is not measuring your carrier. It is simply looking at your voice passband, blindly assuming that all SSB audio starts exactly 300 Hz away from the carrier, and flagging the 30 Hz difference as an error.

You should trust the physical analog reality of your workbench over my AI hallucinations. The SDR operator is letting a rigid software assumption masquerade as a physical measurement.

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

I use a San Jian frequency counter board for my frequency readout. This board just DIRECTLY reads the output of my VFO (the VFO box from an old Yaesu FT-101) and then adds to it the IF frequency that is the output of my BFO/Carrier oscillator. At 14200 kHz the oscillator box is at 8960.13 kHz. The BFO/Carrier Oscillator is at 5239.87 kHz. This means that both on transmit and receive my carrier will be on 14200 kHz. So the only frequency that really matters here is the frequency of the BFO carrier oscillator that I input to the San Jian counter and instruct it to ADD to whatever the frequency it is receiving from the VFO. My BFO frequency is 5239.87 kHz. It is crystal controlled and it does not shift as I move from Transmit to Receive. At 14200 kHz, the VFO is at 8960.13 kHz and it too does not move when I go from T to R. My carrier frequency IS 14200 kHz. So why do operators claim that I am "30 Hz off frequency?"

The passband of my homebrew crystal filter is 5240.2 kHz to 5242.6 kHz. So it is about 2.4 kHz wide. This passband is 330 Hz above the BFO carrier oscillator frequenct. Not the 300 Hz offset that many SDR receivers are expecting. That explains the incorrect comment about being 30 Hz off frequency.

AI Gemini produced the graphic above. I also asked it to describe how this error would occur with modern SDR rigs:

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

Here is exactly how the 30 Hz discrepancy manifests across the specific software interfaces of modern SDR systems:

1. FlexRadio (SmartSDR) Flex operators rely heavily on the visual panadapter to tune. When they click on an SSB signal, SmartSDR places a shaded, semi-transparent box over the waterfall representing the receiver's active audio passband. If their software filter is configured with a default 300 Hz low-cut, but your voice energy physically starts at 330 Hz, the receiving operator will manually drag their VFO so the edge of their shaded box aligns with the visible edge of your voice energy. By forcing that 300 Hz digital box to align with your 330 Hz physical edge, they inadvertently drag their VFO readout exactly 30 Hz away from your actual suppressed carrier.

2. Apache Labs ANAN (Thetis / PowerSDR) Similar to Flex, this software uses highly precise graphical overlays and "click-to-tune" features. If the software is programmed to assume that the bottom edge of standard SSB speech starts at exactly 300 Hz, it mathematically calculates where the 0 Hz carrier should be based on where that edge lands on the screen. Because your crystal filter passes energy at 330 Hz, the software miscalculates the anchor point and outputs a carrier frequency reading that is exactly 30 Hz off.

3. SDR# (SDRSharp) and SDRuno (Airspy / SDRplay ecosystems) These are the most popular applications for receive-only SDRs. They utilize incredibly steep, rigid digital filters. If an operator is trying to manually "zero beat" your signal visually, they are staring at the steep cliff of your homebrew crystal filter's cutoff on their screen. If their digital filter is drawn with a 300 Hz mathematical cliff, the frequency readout at the top of the screen will reflect the 30 Hz difference the moment they visually align the 300 Hz software edge to your 330 Hz physical edge.

4. Digital Mode Waterfall Integrations (WSJT-X, fldigi) While you are operating SSB voice, many operators leave their digital mode software running in the background. These programs map audio frequencies to a rigid grid. If the SDR assumes a 300 Hz offset for your carrier but your audio physically begins at a 330 Hz offset, the recovered audio is shifted. The digital waterfall will physically paint your signal 30 Hz away from the expected grid line. Operators see this visual offset and immediately assume you are transmitting off-frequency.

Ultimately, the SDR software acts like a rigid stencil. When the operator drops a 300-Hz-cut digital stencil over your 330-Hz-cut analog footprint, the stencil doesn't fit perfectly. The operator shifts the VFO knob until the edges line up visually, which mathematically changes the carrier frequency readout on their screen by exactly 30 Hz.

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

PLEASE COMMENT ON ALL THIS AND LET ME KNOW IF I HAVE ANY OF THIS WRONG.

Rex W1REX in England with the Original Tuna Tin 2, aka "The ASR" -- Ancient Sacred Relic. Indeed!

2026-09-23T08:36:01.836-04:00

There he is, Rex W1REX, the esteemed owner of QRPme, the maker of so many great pads for Manhattan boards. He was in the UK for the GQRP convention. And he brought with him -- on loan from the ARRL Museum -- the original Tuna Tin 2 transmitter, the ASR (ANCIENT SACRED RELIC). You can see it in the pictures sent to me by Charlie NJ7V.

Way back in 2014, I met up with Rex at the Vienna Wireless Association's Winterfest Hamfest. There too he had the original TTT with him. I asked him to share some of the mojo from that famed rig with my homebrew BITX transceiver. Here you can see a video of the mojo-ification ceremony:

Thanks to Charlie NJ7V, to the GQRP club, and to Rex W1REX for all the great TTT mojo over the years!

Another Blast from the Past -- Dino KL0S in the early 70s -- A Turner mic, a Vibroplex, an HQ-100, a DC receiver, and a tech library.

2026-09-21T05:55:12.312-04:00

Dino: Yes the parallels are really eerie OM. There is that Turner mic. I still have mine too, but I had to replace the element with an Electret. Mine brags that it is Transistorzed. Wow! It apparently had three transistors in it. Therefore it was a Turner +3. I also had a Vibroplex bug, but I never really used it and it fell apart. Pieces were donated to a restoration of the K3ZO bug in the Dominican Republic. I kept the base, which now holds a straight key that I use very infrequently. There is of course, the Drake. In the other picture (below) I see your HQ-100 (A model). Please tell us more about that DC receiver. Homebrew? Solid State? Band? Where did you get the schematic? I also see that you had a good library even back then. FB OM. I remember fondly the Zoom visit to the Williamsburg club. And I still use the coffee mug! 73 to all. Regards to Toby. Bill N2CQR

Dino writes:

Bill - saw your 15-year old pix on the blog today and immediately found a distinct likeness in my teen ham pix!

And me, WB6FZN at the time, I probably had a similar plaid shirt too:

Come to think about it all of us “of an age” look a lot alike back then. I still have the Vibroplex key, Turner 454-C mic and Drake MS-4 speaker/AC-4 power supply. My dad bought me the TR-4 when I got my General license and that setup was north of $600 if I recall correctly from AES; that was big money for ~1969 as he was a bartender, bless his heart. Sold the TR-4 in Alaska during our first duty assignment with the blessing of my YL Toby KLØSS and got the Drake C-line to replace it which I also still have.

You visited our Williamsburg Area Amateur Radio Club’s “Builders Group” via Zoom during Covid and guys still talk about that session we had with you.

BTW, you can see my first direct conversion receiver in the aluminum chassis sitting on top of my Hammarlund HQ-100A here:

Hope all is well in Northern VA and/or the DR!

73 - Dino KLØS
Williamsburg

Scott K6AUS gets a Drake 2-B from Steve KW4H

2026-09-20T05:22:35.077-04:00

Serial 10219, after refurbishment by Steve KW4H, with the 2-BQ he sent as well perched on top.

https://nomadiq.net/blog/post/a-drake-2b-from-kw4h

For many years, Scott K6AUS has been doing the mathematical analysis of serial numbers on the Drake 2-B receiver. His work has been based on mathematics developed during WWII to let the allies know -- just from serial numbers -- how many tanks the Nazis had. Scott's analysis and the gathering of Drake 2-B serial numbers has been going on since May 2011. See: https://soldersmoke.blogspot.com/2011/05/how-many-drake-2-bs-german-tank-problem.html

and for a Scott's presentation of the math:

https://nomadiq.net/blog/post/how-many-drake-2bs-were-ever-made

We were saddened to learn that in spite of all this work, Scott K6AUS did not have a Drake 2-B himself. Steve KW4H stepped forward to correct this. Steve refurbished a 2-B and sent it to Scott. FB Steve. See the link above.

We have been chronicling Steve's work on this partictular Drake 2-B. Steve also wrote an excellent two part article on this receiver for Electric Radio magazine. Part I recently went out. Part II is coming.

Thanks to Scott for all his analysis of the serial numbers. And thanks to Steve for his amazing generosity.