Homebrew Receiver -- AG5VG's 20 Meter "Mythbuster" Receiver

Michael has the receiver done and is wisely heeding Farhan's advice about pausing to enjoy the homebrew sounds.  

I was pleased to see someone else using the FT-101 VFO.  Great piece of gear.  

On to the transmitter!  

Fernando's Rigs -- Vintage Ham Radio Receivers

Thanks to Rogier PA1ZZ for sending me this YouTube link.  It is a truly wonderful channel from Spain. Not only the Collins Gold Dust Twins, but also lots of great (and not-so-great!) older receivers.  SP-600s, S-38s,  Rhode and Schwartz rigs, lots of great stuff.  Go to the "Videos" link and enjoy the Thermatron goodness.   Thanks Rogier!  And thanks Fernando! 

 https://www.youtube.com/@jonglei

SolderSmoke Artificial Intelligence -- Where the AI Podcasts Came From

 

The aticle and the podcast (don't worry, it is NOT an AI podcast) explain how we were able to generate the AI podcasts we presented during the last two days. 

https://www.theverge.com/24249388/notebooklm-google-steven-johnson-vergecast

The audio podcast feature was introduced only ONE WEEK AGO!  Rarely have we been so close to the cutting edge!  

The product itself first launched in 2023 as Project Tailwind, and has since been rebranded and expanded in big ways. Just last week, the team launched Audio Overviews, which generates a podcast — with two chatty hosts, plenty of back and forth, and a truly remarkable penchant for the phrases “deep dive” and “buckle up” — based on the information you provide. It’s fascinating, it’s complicated, and it’s getting better really fast.

Thanks to Bob for alerting me to all this! 

AI Podcast #2: Here is Another Short Podcast ABOUT SolderSmoke.

Click here for the second "About SolderSmoke" podcast. 

 http://www.soldersmoke.com/About SolderSmoke 2.mp3

This one looks not at the SolderSmoke Daily News blog, but instead at the SolderSmoke podcast itself.

I was delighted to see the inclusion of Pete, Dean, Farhan and Mike Rainey!   This was really great.  

Look, it is not perfect.  There are errors.  But probably about the same number of errors that you would get from real, human hosts, right?    Voltaire told us not to let the perfect be the enemy of the good.  And I find this to be amazingly good. Look, it is so good that it is kind of scary, right?

Before you get too critical realize how this has been done:  I did nothing more than load the SolderSmoke Podcast Archive website into GPT-like model. Then I asked it to produce a deep dive podcast.  That's it.  About 5 clicks.  It developed the podcast in about 3 minutes.  I did the same thing yesterday but with the SolderSmoke blog.  And this is only the beginning.  

AI Podcast #1 -- A new (experimental) Podcast About SolderSmoke Daily News

GET THOSE SOLDERING IRONS HEATED UP!  WE'RE GOING DEEP TODAY, DEEP INTO THE WORLD OF HAM RADIO! 

Click here for the new experimental podcast: 

http://www.soldersmoke.com/About SolderSmoke 1.mp3

I am looking for comments on this.  What do you think?  

Please post comments below or send me an e-mail. 

Thanks and 73 

A Clean Vintage Ham Radio Transmitter: The Collins 32S-3

In an article on IMD and splatter,  tech guru Rob Sherwood noted that the cleanest tranmitter he had ever owened was the Colling 32S-3.   Here is the article.  https://soldersmoke.blogspot.com/2024/09/sherwood-its-time-to-clean-up-our.html

In it, you will see thar Rob has the spectrum anayser two tone test to prove his point.  

This got me wondering:  Why was the Collins transmitter so clean.   Today I looked at some ot the tech info on this rig.  I think I have found the answer. The Collins Collectors Association has a great page on the 32S-3: https://collinsradio.org/cca-collins-historical-archives/the-equipment-of-collins-radio/the-grey-boxes/32s-3/

The key lines are these:  

Click on the paragraphs or go to the link for a clearer view 

I think the explanation of Collins'32S-3 cleanliness is due to 1) Thermatrons in the final stages and 2) Negative feedback to take down any IMD products that might appear due to non-linearities in the finals.   

There is nothing magical in that technique.  Heck, we could homebrew that today.  We could build HDR stations (perhaps transistor-tube hybrids) that would be cleaner than their commercial SDR cousins. 

Ham Radio -- How To Build Stable Oscillators

Spasibo Vasily!  

Wow, thanks a lot Todd.   There is some great wisdom in your video.  You clearly demonstrate that it is possible to build your own stable LC VFOs.  Sure, for many the arrival of the synthesizer chip put an end to this kind of project.  But some of us still want to fully homebrew all the stages in our rigs, and not be dependent on mysterious chips and software written by others.  

I really liked the way Todd acknowedged the tremendous contributions of Wes, and Roy, and Rick and others. 

Of course, all of Todd's recommendations are right on the mark.  I have been following most of them (but I do fall short and occassionally use a Manhattan pad or two).  Todd even gets into the mysterious and arcane practice of boiling (three times!) toroidal transformers.  I do have a preference for air-core coils, but that boiling sounds like fun. 

One thing that Todd and Brad might also want to consider:   tuning linearity.  Too often LC VFOs end up having the frequency spacing very close at one end of the dial and very broad at the other end.  "Bob's Electron Bunker" provides some great tools for alleviating this problem:

https://soldersmoke.blogspot.com/2022/09/the-cure-for-frequency-bunching-up-in.html

Thanks again Todd! 

AG5VG's Homebrew 20 meter Superhet (with a CW rig Coming) (Video)

 Michael AG5VG finished this receiver last weekend.  He hopes to build a CW transmitter using an output of the Si5351.  Obviously I defer to Pete on that one.  Good going Michael.  I think it sounds great and looks even better.  

Vulnerable MOSFETS in NASA's Europa Clipper

 

Oh man, this is terrible.  Just months before launch of the Europa Clipper mission to Jupiter's satellite, they discovered that some of the MOSFETS in the spacecraft might get fried by the Jovian radiation.  1500 MOSFETS.  Ouch.  Details here: 

https://futurism.com/nasa-disastrous-flaw-spacecraft

"QRP Classics" The Book that Got Me Started in Homebrew

https://soldersmoke.blogspot.com/2022/09/fixing-up-old-homebrew-rig-barebones.html

A question this morning from Scott KQ4AOP caused me to Google this old book    On page 59 I found the article about my first transmitter.  Someone has put a copy of the entire book on the interenet.  Here it is: 

https://ham.v4.si/books/QRP%20Classics%20-%20The%20Best%20QRP%20Projects%20from%20QST%20and%20the%20ARRL%20Handbook.pdf

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. 

IMD in Transmitters -- Splatter? Or Signal Strength?

https://www.newsvhf.com/conf2024/PresPapers/WA1MBA-IMD_in_Transmitters.pdf

Here is a good (and very recent) article on IMD ("splatter") produced in transmitters. The focus is on VHF, but much of this is relevant to HF operators.  I found the footnotes on the ARRL "Clean Signal Initiative" to be worrisome.  They seem to just be assuming that all ham operators will be using commercial gear, and the "OEM" needs to be made to meet certain standards. This seems to leave the homebrewer out in the cold.  I can see where someday soon, the "standards" will exceed the capability of analog homebrewers.  That would be bad.  

The role that signal strength plays in the perception of "splatter" is often misunderstood by the "waterfall police."  We often we hear some irate waterfall policeman screaming that,  "You are 40 over and far too wide."   Here is a good quote from the article on this point: 

"If you have a calibrated spectrum display (as many SDR’s are these days), you can directly measure the level difference in dB. If it is 30 dB or more, then it could be an acceptably “clean signal”, even if it is bothersome. Most ham voice communication is conducted with less than 30 dB signal/noise, and in that case the unwanted IMD is buried in the noise."

And even in a low noise environment,  if the signal is 40 db over S9. that would mean the signal PEP is at -33dbm.  If the IMD products are 46 db down from the signal peak, that means your IMD products are -79 dbm.  That is S-8!   That signal will look quite wide in the waterfall, but it would be within FCC specs, right? The problem here is not so much distortion, as signal strength.  And let's remember that "legal limit" is usually a misnomer:  FCC regs require hams to use the minimum power necessary, not 1.5 kW on every single QSO.