SA2CLC Fixes the Cavity Resonator on his HP8640 -- Not for the Faint of Heart!

 

https://sa2clc.blogspot.com/2025/01/hp8640-died-this-is-me-catching-up-on.html?m=1

Clip Leads Made with FAKE WIRE! Buy Good Ones from PARTS CANDY!

We don't see many videos about clip leads,  but this one fits in well with our esoteric subject matter. 

Carlos of Parts Candy (our sponsor) responds: 

Interesting video. Yes the clips we make are nickel plated steel but the wire is tinned copper. When I was making custom orders I made some custom clip lead sets using 100% copper clips for a few people who really needed the low resistance. In most applications the steel clips should be fine. The resistance for 12” clips is about 12mOhms and the 32” clips are around 24mOhms, iirc.

The bottom lines:  1)  Don't scrimp with a crimp -- get a good solid soldered clip-wire connection from Parts Candy. 2) Parts Candy wires are not fake.  They are tinned copper 3) The metallic composition of Parts Candy clips does not degrade performance. 4) But if a customer really needs copper clips, Carlos can make them too. 

Parts Candy web site:  https://www.partscandy.com/

Using a Photomultiplier THERMATRON to Detect Single Photons

I've been a fan of Jeroen's YouTube channel for a while now.  He has a very nice approach, combining theoretical knowlege with practical experiments and equipment builds.  Here we see him using a photomultiplier tube and a board acquired in flea market to build his photon detector.  

This video has a lot to offer us.  First, there is a single thermatron.  There is a tube socket.  There is a (really small!) high-voltage power supply.  He uses an oscilloscope. There is a laser.  There are photons.  And at one point, a single photon.  

Having recently built a simple Wilson Cloud Chamber, my attraction to this device is easy to explain.  I suspect our friend Grayson will be interested in it for Thermatronic reasons.   There is a Part II.   Check out the YouTube channel: 

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

Here is more info on the channel and it's creator: 

Hi, my name is Jeroen and on the Huygens Optics channel I publish videos on personal projects. My main fields of interest are optics, mechanics and photolithography. The videos aren't targeted towards a general audience but for people with a passion for science and technology (e.g. my fellow nerds). The channel is named after the famous Dutch mathematician, astronomer and inventor Christiaan Huygens (1629-1695). He was the first to publish a mathematical description of the wave properties of light, and also discovered Saturn's rings.

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

Thanks Jeroen

Bill N2CQR Builds Yet Another Mythbuster Transceiver

 This one is for 20 meters (no need for 75) and will go to the Dominican Republic.

6 crystal filter at 5.2 MHz. VFO from old Yaesu FT-101 Termination Insensitive IF amplifiers using boards from Mostly DIY RF No RF amp ahead of the mixer. First mixer is homebrew diode ring. Bandpass filter has 4 LC circuits. Steep skirts. Low insertion loss. Bal Mod/Product detector has two diodes (singly balanced) Carrier osc is crystal controlled and homebrew. Audio amp starts with a 2N3904 amplifier followed by an LM386 board. Transmitter portion will be done next.

The crystal filter as seen on the Antuino

Filter on the blank board. 

Bandpass filter (-20 db = 0)

VFO box, carrier osc, Bal Mod/Product Detector, AF amps

The Antuino looks at the Crystal Filter

Sherwood: "It's Time to Clean Up our Transmitters"

 

http://nc0b.com/qst-article/NC0B-QST-Nov-2019.pdf

As an analog, HDR, discrete component, radical homebrew fundamentalist, obviously I have been concerned about all the hype about SDR.  SDR advocates often make it sound as if those of us who build with discrete analog components (crystal filters!) are hopless troglodytes, about to be thrown on the ash heap of radio history.  Or something like that.  They sort of imply that without the cleansing benefits of SDR, our signals will remain hoplessly dirty. 

I find it interesting that Sherwood concluded that the cleanest transmitter he ever owned was a Collins 32S-3!  He compared the two tone output of this old rig to that of a modern transceiver.  This was in 2019.  See above.  HDR wins. 

Don't get me wrong.  I want to clean up the signals from my HDR rigs.  But I am encouraged by Sherwood's remarks.  I do not think I will have to go SDR in order to have a clean signal.   I may just  do some two-tone tests on the rigs,  make some adjustments, and maybe build a class A Thermatron .1 kW linear. 

A Paraset and the Heathkit SG-6 Signal Generator (Video)

Mike WU2D put out this nice video (above) about whether or not he should part out his Heath SG-6 signal generator, using the parts in a Paraset construction project.  I faced a similar question years ago: 

https://soldersmoke.blogspot.com/search?q=SG-6

I just solid stated the SG-6.  I was influenced by Farhan and the drinking straws that he picked up with his kids at a McDonalds in Hyderabad. 

As with the QF-1, I say to Mike: GO FOR IT OM!  You need those parts for other projects.  Don't feel bad about the SG-6.  But keep that switched coil assembly -- it is quite useful. 

ANOTHER Great Workshop

As I get ready to build the SolderSmoke Shack South, the Radio Gods (well at least YouTube) keep sending me these workshop videos.  Today's is also for a shop specializing in the repair of vintage audio gear, but the lessons-learned and observations are also applicable to a ham radio workshop.  This fellow's shop is in New York City, where space is very limited.  Check it out.  Lots of great ideas here.   

And check out the Novalux Stereophhonic channel:

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

 

Some Really Amazing Test Gear

Wow. Really great test gear, and an amazing parts collection.   This guy even gets a "nice workshop" comment from Mr. Carlson.   Pac1085 seems to be in Rochester N.Y. and he says he specializes in the repair of vintage audio gear.  He should have more subscribers.  Does anyone have more info on him?  

Here is his channel:  https://www.youtube.com/@pac1085/featured

Why we have "BW Limit" Switches on our Oscilloscopes

Dean KK4DAS asked me why we have these switches on our 'scopes.  I didn't know.  Dean asked Alan Wolke W2AEW.  Alan knew: 

Alan Wolke wrote: 

Interesting background on the 20MHz vertical BW selection. This feature has existed on the vast majority of all oscilloscopes since the 50s or 60s (both analog & digital). When I explored the history of this, I spoke to some of the folks at VintageTek.org, and wound up having a chat with THE engineer that did it first!  Tt was John Addis, designer at Tektronix. 

At the time, Tektronix was located in Portland Oregon. While working on a wideband vertical preamp for a new scope (the 7A11 vertical plugin for the 7000 series scope), John Addis was plagued with interference from the local television broadcast station in the 50MHz band. So, he popped in a 20MHz low pass filter that he could switch in/out so that he could complete the work on the preamp. Since it was deemed useful, it was left in the design. 

 

And, since Tektronix added a switchable 20MHz low pass filter  in their scope, and Tek was the leader in oscilloscope technology, other manufacturers followed suit, and this feature has "stuck" as a staple in vertical setting controls. 

 

The main reasons you'd use this filter would be to improve the signal to noise ratio (SNR) for signals when their frequency content is below 20MHz.   You've probably noticed that, even without any signal connected, the thickness of the trace is thinner when you engage the 20MHz filter. 

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

Alan sent a link to a Wiki page about the 7A11 that John Addis was designing.  Alan says this places the initial inclusion of the 20 MHz BW Limit filter to the mid 1960s: 

https://w140.com/tekwiki/wiki/7A11. 

Thanks Dean, thanks Alan!  

Radio Items Picked-up at VWS Winterfest 2024 Hamfest

As always, click on image for a better view

Above you can see what I picked up at the Vienna Wireless Society's 2024 Winterfest Hamfest. 

-- On the left in the blue box is an MXM Industries SuperRX/TX 40 transceiver. It is a kit from a Texas company.   Superhet receiver with IF at 455 kHz.  Crystal controlled CW transmitter on 7040 kHz.  The oscillator works, but so far no receive signals.  I will have to troubleshoot.  Does anyone have a schematic? 

-- Behind the MXM there is a nice box marked "Diode Detector" I opened it up and there is just a solid state diode and a 50 ohm resistor to ground.   Box may be useful. 

-- I got a couple of books: "Weekend Projects" 1979 from ARRL, and "A History of QST -- Volume 1 Amateur Radio Technology 1915 - 2013" 2013 from ARRL. 

-- On top of the Weekend Projects book you see a "Crystal Holder" from Gross Radio of New York City.  W1UJR has some good history on this company:  https://w1ujr.com/written-word/gross-radio-company-circa-1931/  This device seem to be intended to hold in place a raw piece of quartz!  Cool. 

-- To the right of the books there is a serious-looking VFO.  One dollar!  Deal!  It is a CB VFO, but the markings say it puts out 5.44 to 5.99 MHz.  So it should be useful.  The dual speed dial is very nice.  

-- Above the VFO is a nice step attenuator from the "Arrow Antenna" company of Loveland Colorado. 

-- Further to the right are some Electric Radio and Antique Wireless Association magazines that Armand WA1UQO gave me.  Really nice.  The AWA mags have a very thoughtful piece (warts and all) on Jean Shepherd.  And the ER pile has an article by Scott WA9WFA that mentions my work on the Mate for the Mighty Midget receiver.  Thanks again Armand! 

-- I also got some ADE6+ surface mount mixers.  The price was right! 

Thanks to VWS for putting on this great hamfest! 

SolderSmoke Podcast #249 -- Travel, Pete's 6BA6 rig, Books!, VFOs, SDR, Computers, Spectrum Analysers, Transistor Man! MAILBAG

New VFO for 15-10 Transceiver

Schematic below

SolderSmoke Podcast #249 is available:  http://soldersmoke.com/soldersmoke249.mp3

There is also a video version of this podcast: https://youtu.be/5xyaYivtOhw

Travelogue:  

HAPPY VETERANS' DAY TO PETE AND GRAYSON AND TO ALL THE OTHER VETERANS WHO ARE LISTENING. 

Trip out to San Francisco. Sticker placed on the corner of Haight and Ashbury:  See picture below.  Note other sticker.  Really Groovy! 

Cuban Cacharreo! Andy CO2AFV's Knack Story  https://soldersmoke.blogspot.com/2023/10/a-cuban-knack-story-and-pandemic-sits.html

Bill's DXCC-100.  DONE.   

Tribal Wisdom:  W1REX on HRWB https://soldersmoke.blogspot.com/2023/11/listen-to-rex-w1rex-lots-of-tribal.html

Pete's Bench:

Pete's 6BA6 rig

Pete's 6BA6 Rig

Pete Re-invents the Shirt-pocket SSB Rig

Pete's remake of the ShirtSleeve Transceiver

Pete Builds Two Computers 

Pete Adds a Second Band to his Homebrew SDR 

 

SHAMELESS COMMERCE DIVISION:  

BEZOS BUCKS ARE BACK!  PLEASE  BUY THERE! >>>>>>>>>>>>>>>>>>>>>>>

Mostly DIY RF:  Work proceeds in the Oregon Silicon Forest on P3ST kit development. Todd is confident the P3ST will be released on December 18th.Many other kits available now:  https://mostlydiyrf.com/ 

Sign up for the newsletter:  https://mostlydiyrf.com/subscribe/ 

Bill's Bench: 

Rebuild of the 15-10 VFO (for improved Dial Spread) (with yet another QF-1 capacitor) https://soldersmoke.blogspot.com/2023/10/dial-scale-linearity-spreading-out.html

Why Building for 10 meters is harder: https://soldersmoke.blogspot.com/2023/09/why-building-for-10-meters-is-harder.html

Copper Tape shielding of 15-10 rig. 

Crushing Spurs with Better Bandpass Filters (see blog post) https://soldersmoke.blogspot.com/2023/09/crushing-17-and-12-meter-spurs-with.html

Another 15-10 rig in the works... for SSSS.   Boards are accumulating... 

More problems discovered with the Herring Aid 5 Receiver . Lots of SS blog posts  Comment from Rick WD5L.  ) https://soldersmoke.blogspot.com/2023/10/a-big-error-discovered-in-1976-qst.html   Did you try to build one?  Did you succeed or did you fail?  Please let us know. 

The Basil Mahon books (blog posts) https://soldersmoke.blogspot.com/2023/11/basil-mahon-is-author-for-us-he.html

The Sunburst and Luminary book of Don Eyles (blog posts) 

The Art of Electronics by Horowitz and Hill (blog posts) 

Spectrum Analysers:  Tiny SA Ultra https://soldersmoke.blogspot.com/2023/09/the-tinysa-ultra-spectrum-analyser-video.html  and Polarad 632C-1; George WB5OYP gave me one of these spectrum analysers  (I NEED a manual! Does anyone have a manual or a schematic? )  : 

Polarad 632C-1

Stabilizing the EB63A (with Pete recommended LP filters from e-Bay. 

MAILBAG:

TRANSISTOR MAN T-SHIRTS!  Thanks to Roy WN3F! 

Todd VE7BPO on AF amplifiers.  Thanks Todd.  

Wes W7ZOI -- Always a privilege to exchange e-mail with Wes. 

E-mail from Jay Rusgrove W1VD. About the Herring Aid 5. 

E-mail from Eamon Skelton EI9GQ!  Amazing! 

HB2HB with Denny VU2DGR https://soldersmoke.blogspot.com/2023/09/hb2hb-contact-with-denny-vu2dgr.html

Nick M0NTV on diode matching for ring mixers: https://soldersmoke.blogspot.com/2023/10/does-matching-matter-diode-matching-for.html

Paul Taylor VK3HN on the new Elecraft CW rig. 

Dean KK4DAS fixed the noise in his Hallicrafters SW receiver.  A long battle, finally won. 

Dean also in contact with G3UUR. 

Ramakrishnan VU2JXN helping me set up a backup of blog on WordPress.  

Mark KA9OOI noticed that SS podcast archive appears gone.  In fact just temporarily relocated to http://soldersmoke.com/podcastarchive.html

(SS PODCAST Archive temporarily relocated to http://soldersmoke.com/podcastarchive.html) 

Andreas DL1AJG - Crystal radio video. https://soldersmoke.blogspot.com/2023/10/building-crystal-set-videos.html

George N2APB on the Herring Aid 5

Grayson KJ7UM experimenting with Varactors and Thermatrons! 

Thomas K4SWL on Mattia's DC receiver. https://soldersmoke.blogspot.com/2023/10/mattia-zamanas-amazing-direct.html

Bob Weaver of Dial Bandspread Linearity  fame.  Electron Bunker

Mike Bryce WB8VGE QRP Hall of famer -- he too couldn't get the Herring Aid 5 working. 

Kirk NT0Z wrote about the Wayback machine.  But this former ARRL staffer he also tried and failed to get the Herring Aid 5 going.  Way back when... https://soldersmoke.blogspot.com/2015/03/kirks-herring-aid-tuna-tin-and-regen.html

New 15-10 VFO with schematic

Dial Bandspread (Before)

At corner of Haight and Ashbury

Another Evaluation of the TinySA Ultra (with Teardown) (Video)

More info on using the TinySA Ultra. 

-- Makes me wonder if it makes sense for me NOT to enable Ultra mode now.  I am not going into the UHF range.

-- Waterfall!  Sig Gen! 

-- Kerry got a lot of distortion when listening to FM broadcast signals.  I wonder if this is due to the Tiny SA detector being an AM detector? 

-- Teardown was very cool.  

-- Comparison to the HP spectrum analyser was very illuminating.  Bottom line:  TinySA Ultra gives you a lot of capability for $150.  

 

The TinySA Ultra Spectrum Analyser (video)

I got mine this week, and I've been playing with it.  When I spoke to Dean KK4DAS, I asked what he thought the first thing I did with it was.  He guessed that I tried out the greatly improved Resolution Bandwidth.  Good guess, but not quite:  I tried out the  "listening" feature on this SA.  You will recall that the plain-vanilla, non-Ultra TinySA required a hardware mod to allow for listening.  Dean had told me that the Ultra came with a headphone jack.  Indeed.  I fired it up and was able to listen to 1220 AM and also to the FM broadcast stations in the area.  With the FM stations, I'm guessing I was using a form of slope detection (IMSAI guy says it detects AM).   I tried to see if I could see/hear stations on the ham bands -- so far, no luck.  I'm not sure why, but I will work on this.  

The IMSAI guy video (above) does a great job in comparing the TinySA Ultra to a "real" spectrum analyser.   I think it compares very well.  

One note on where I got mine:  I ended up getting it from R&L Electronics, the recommended U.S. dealer for the device.  I had tried getting it (cheap) through AliExpress.  This didn't really work out.  The tracking info from AliExpress showed that the box had made it to my local post office, but I never got it.  It may have been that they just didn't take the complete mailing address from PayPal.  In any event, I was able to get a refund from PayPal, so no loss here.  R&L turned out to be a great source. 

Ultra, of course. 

Crushing Spurs with Better Bandpass Filters

PA3AKE's passband (on screen) an mine (on NanoVNA) 

While I was away in the Dominican Republic (3-9 August 2023),  I was thinking about spurs.  While there I watched Nick M0NTV's video about mixers.  The video was all great, but I was especially taken by the way he used a spectrum analyser to evaluate the output of various mixers.  This made me think that I should do the same thing with the output of each of my dual-band BITX rigs. 

I was especially worried about the output from my 17-12 rig.  The IF is at 21.4 MHz.  The VFO runs around 3.5 MHz.   So if you add the IF and the carrier oscillator signal you get to 12 meters.  If you subtract them you get to 17 meters.  But you need some good bandpass filtering to sufficiently knock down the unwanted output from the mixer.  And the BP filter should be sufficiently narrow to take out any remnants of the carrier oscillator signal. I had taken the easy way out and had used simple dual-tuned-circuit (DTC) filters.  I started to wonder if these simple BP filters would be enough to knock down the 12 meter signal while on 17 and the 17 meter signal while on 12.  I pulled out my NanoVNA to look at the passbands: 

Here is what the 17 meter DTC filter passband looked like. The cursor is at 29.6 MHz and you can see that near the 12 meter band it is only providing about 21 db of attenuation.  That is not enough. 

And here is what the 12 meter filter looked like. Here the cursor is at 18.150 Mhz and shows about 25 db of attenuation at this frequency.  Again, not enough.  

The results are as you would expect: I could see 24.9 MHz signals in the output when I was on 17 meters, and I could see 18 MHz signals in the output when I was on 12 meters.  The spurs weren't strong, but they were there.  I knew that more robust BP filters would help.  

At first I used the circuits prescribed by Martein PA3AKE.  He used larger toroidal cores, I used smaller T-50-6 (yellow) cores.  The results were very similar.  See the first picture on this blog post. 

The results were really good.  See pictures below.  I was using a TinySA with the signal fed through a 50 ohm 30db attenuator.  I was putting a 1 kHz signal in to the mic input.  

This picture shows the 12 meter output and the now non-existent 17 meter spur.  The cursor is at 18.142 MHz:    

This picture shows the 17 meter signal and the now non-existent 12 meter spur. The cursor is at 24.993 MHz.   We can see some second harmonic signal getting past the LP filter -- I will fix this.  

Then Farhan commented on Martien's filters, noting that they are all in the "LSB" configuration.   You can see from the charts below how they would be really good when you are trying to use the "difference" output from your mixer while knocking down the sum output,  but not vice versa.     So I built new USB filters for 12 meters,  and for 10 meters in my nee 15-10 rig.  I got better results on the two "sum" bands in my rigs (10 and 12 meters) 

Phase Noise and the Radio Amateur

A weak signal disappears in the phase noise of the stronger signal.

The March 1988 QST provides a relatively clear explanation of what phase noise really is:

https://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1988/03/page14/index.html

Highlights: 

Phase noise is an undesired variation in the phase of the signal. In this case, an oscilloscope shows that the time between zero crossings of the signal varies over time when compared to the zero crossings of an ideal sine wave. An exaggerated example of phase noise is shown above.

Phase noise on an oscillator signal has exactly the same effect as frequency modulating the oscillator with noise.

Whenever a carrier is passed through a mixer, the phase noise of the oscillator driving that mixer is added to the carrier.

Phase noise on a transmitted signal causes effects identical to phase noise generated in a receiver.

Any signal that reaches a mixer in the receiver is modulated by the phase noise in the local oscillator driving that mixer. As such, the signal appears to have at least as much phase noise as the local oscillator. Thus, sufficiently strong signals off the receiving frequency can degrade receiver sensitivity by raising the noise floor at the receiving frequency. Receiver dynamic range is reduced as the noise floor rises.

With a frequency-shift-keyed or- a phase-shift-keyed signal, the close-in phase noise limits the maximum bit error rate that the system can achieve. Both of these effects can be quantified once the communications system is defined. With an SSB voice signal, the effects are much harder to predict, but excessive phase noise does degrade SSB signal intelligibility to some extent.

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

Receiver guru Rob Sherwood provides some very useful historical background on his web site:

http://www.sherweng.com/documents/TermsExplainedSherwoodTableofReceiverPerformance-RevF.pdf

Phase Noise: Old radios (Collins, Drake, Hammarlund, National) used a VFO or PTO and crystal oscillators to tune the bands. Any noise in the local oscillator (LO) chain was minimal. When synthesized radios came along in the 70s, the LO had noise on it. It is caused by phase jitter in the circuit, and puts significant noise sidebands on the LO. This can mix with a strong signal outside the passband of the radio and put noise on top of the weak signal you are trying to copy. This is a significant problem in some cases: You have a neighboring ham close by, during Field Day when there are multiple transmitters at the same site, and certainly in a multi-multi contest station. You would like the number to be better that 130 dBc / Hz at 10 kHz. A non-synthesized radio, such as a Drake or Collins, has so little local oscillator noise the measurements were made closer-in between 2 and 5 kHz.   

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

Experimental Methods in RF Design (EMRFD) has this to say about phase noise:

"The local oscillator is a critical part of any communications system. Modern transceiver performance is often compromised by LO systems that suffer from excess phase noise, effectively limiting the receiver dynamic range. While quiet oscillators, those with low phase noise, can be built using traditional methods, these circuits often lack the thermal stability of a synthesizer.... Frequency synthesis is not, however, the answer to all the LO problems presented to the experimenter.  Some PLL synthesizers are burdened by excessive phase noise. Those using DDS, while quieter, emit spurious outputs, often in profusion.  Both use an excess of digital circuitry that can often corrupt a receiver environment."  page 4.1

   

"At first glance, phase noise sounds like an esoteric detail that probably has little impact on practical communications.  This is generally true." page 4.12 

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

Hans Summers G0UPL analyzed and measured the phase noise of the Si5351a chip: 

http://qrp-labs.com/qcxp/phasenoise.html

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

DC4KU appears to be using the crystal filter method used by Hans: 

https://dc4ku.darc.de/Transmitter-Sideband-Noise_DC4KU.pdf

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

Martien PA3AKE has done a lot of great work on this topic.  See: 

https://martein.home.xs4all.nl/pa3ake/hmode/dds_pmnoise_intro.html

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

Dean KK4DAS commented on the phase noise video of the IMSAI guy: 

Watching the video I was reminded of Segal's law roughly paraphrased as follows.:

A man with one spectrum analyzer knows his phase noise. A man with two is unsure.

The TEK 465 'Scope Used to Create Pong and the Apple II

Wow, this is almost enough to make me take another shot at repairing my TEK 465.  

 

Part III: Curious Marc Repairs an All-Discrete Freq Counter: DO NOT ATTEMPT REPAIR OF CAVITY RESONATOR

I love all the "DO NOT ATTEMPT" warnings.  Wow, even HP got so skittish about this stuff.  Marc has a great sense of humor and notes that, "no cavity resonators were harmed in the production of this video."   I like the description of the mixers and the photo of the mixer antennas. 

CuriousMarc Repairs an old DISCRETE COMPONENT HP Frequency Counter

I really liked this repair video from CuriousMarc (aka AJ6JV).  This counter pre-dates the use of integrated circuits -- it is all discrete transistors.  Near the end, Marc mentions how this made this repair "like debugging a big integrated circuit, but with access to each transistor -- this made it quite satisfying."  I hear ya Marc -- with big ICs maybe all you would get to do would be to swap out a single IC.  There would not be much of a challenge there.  

With the older, discrete circuitry you get a good view of how Marc troubleshoots -- how he finds the precise points where the device is failing.  Note his use of the old HP paper manuals. I know this is an old guy thing, but I think the paper manuals (as opposed to the online versions)  just make the process easier.  Note too that Marc at one point had to go back to microfiche. 

The transistor tester Mark used was very cool. 

The whole physical structure of the HP device is very similar to my NYC HP8640B.  Thanks again Steve Silverman and Dave Bamford. 

I will look at Parts II and III of this series soon.  

Apex Surplus in Los Angeles

The Polaroid camera for the Tek 'scope was pretty cool.  And the comments about the Simpson 260 made me feel good about finding one at a recent hamfest, but I don't think mine is an extremely rare Model 2.   

Winterfest Loot: Who Can ID the Homebrew Receiver?

First a big congratulations to the Vienna Wireless Society and its President, Dean KK4DAS.  In spite of low temperatures that made the Winterfest Hamfest live up to its name, this year's 'fest was a big success with excellent turnout both by buyers and sellers.  There were a LOT of older rigs -- on one table I saw three HT-37s.   It was all great. Here is a video of the hamfest.  https://www.youtube.com/watch?v=oheht5jCuKE&t=619s  This was shot early on Sunday morning March 19, 2023, about 30 minutes after it opened.  An hour later there were a lot more customers. 

One of the first things I bought was the item pictured above.  I bought it mostly because we are currently building 40 meter receivers with the local high-school students.  I didn't have a screw driver, so I couldn't open up the box.   Something was rattling around in there.   I worried that the box might be mostly empty.  Or that it would have one PC board with a sad collection of ICs.  But in the hope that I would find something truly homebrew, I bought it.  

Below are pictures of what I found inside.  Can anyone tell us what this is?  ( I recognized it immediately.)  More on this device in due course. 

Other loot from the 'fest: 

The one on the left I've been using since around 1998!  It is getting beat up.  I bought the one on the right at the 'fest.  It is in much better condition.  5 bucks.  TRGHS. 

I always wanted one.  I had nice leather case, but I gave it to Dick Dillman years ago. I now feel like a real boatanchor guy.  I got for 15 bucks.  I see on Amazon they are selling for $466! 

I had one as a kid.  Will be useful in the DR.  In great shape. 

Eamon Skelton's book was a great find.  As were the early editions of SSB for the Radio Amateur.  Eight bucks for the whole lot.

I like homebrew speaker enclosures.  They add soul to the new machine. Perhaps a prize for the high-school project.  Three bucks. 

Finally, this thing.  Plagued by guilt for past cannibalizations of QF-1s,   I was going to pass on this one, but I realized that my friend Dean KK4DAS would be on his way, and if I didn't take it (and extract the variable capacitor) he would.  So I bought it.  But I may leave this one as is, for possible use as the The Radio Gods intended.  It could use some cleaning up.  It seems to have a coat of nicotine. Ten bucks. 

I also picked up a few larger knobs that may be of use with the high-school receivers.