Pil Joo's Homebrew Superheterodyne Ham-Radio Receiver

It is just very cool to see someone build a superhet and get it to work.  For so many years amateurs were told that "homebrew receivers are too hard."  Even simple regens or direct conversion rigs were sometimes seen as beyond the abilities of amateurs.  But here we see another reminder of this not being true.  Even a superhet -- which is a lot more difficult than a direct conversion receiver -- can be homebrewed by an amateur builder.  Three cheers for Pil Joo! 

He wrote on the SolderSmoke Facebook page: 

I finished my first super het receiver. It's for the 40m band. It consists of: bandpass filter, tuned amp, diode ring mixer, wide band amp, crystal ladder filter, wide band amp, then SA602 + LM386 combo. I learned tons as i put all the components. First two amps are my design. The third amp is bga2866. The bandpass filter is what i posted a few days ago. I planned to make another one but with 2.5db insertion loss i thought it was good enough.

The result is actually quite good. I can hear everything a local kiwisdr can hear. Now, I have lots of ideas about how i can improve, but that will be another radio.

Pil Joo

A 40 Meter Direct Conversion Receiver from M0NTV -- With some SolderSmoke Comments

Nick's video appears above. 

First, let me say FB Nick.   It is nice to see you making use of the AGC amp designed by Wes and Bob,  using the board from Todd's Mostly DIY RF, using a mix of homebrew pads and Me-Squares  from Rex, and finally the Franklin Oscillator that we spent so much time talking about on SolderSmoke.  

But here are some comments:  

-- I still don't think you need that RF amplifier in front of the mixer. And I suspect you would be better off without it.  We did not use one in our high school 40 meter project, and never missed it.  In fact, on one version of the high school receiver I even put in a simple 10k pot as an attenuator (no RF amp).  Even up on 20 meters, I do not have an RF amplifier ahead of the diode ring mixer on either of the Mythbuster rigs I have built.  Nick,  maybe experiment a bit more and try the receiver just going from the BP filter into the mixer and see what happens.  

Note that Wes W7ZOI DID NOT have an REF amp ahead of the diode ring mixer in his original 1968 40 meter Direct Conversion receiver (the one that launched the solid-state DC recevier revolution): 

-- The Franklin oscillator is an interesting, but complicated circuit.  The gimmick is, well, gimmicky.  Here is the thing:  You can achieve similar levels of stability using simple conventional, single transistor oscillators.  We dispensed with the variable capacitors, and used PTO--style variable inductors. They worked fine.  This Franklin oscillator still does seem to drift a bit, right?   I would ground the board to the inside of the metal box.    

I would also try putting all the stages on a single ground plane.  This might help.  

Charlie "Red" NJ7V Builds an Oscillator -- Manhattan Style

https://www.youtube.com/shorts/7t_E5N4CQxg

Red did a nice job building, then explaining, this 18 MHz crystal oscillator.   I especially liked his use of Manhattan techniques, and the way he explained his effort to make the new circuit work.  Too often builders expect a circuit to work right away.   This often doesn't happen, and the new circuit requires some troubleshooting.  Red did this with this circuit and got it working.  

Red has a nice YouTube channel: https://www.youtube.com/@RedSummitRF.  It is focused on POTA, but we hope it has more and more homebrew stuff like this.  

Thanks to Rogier PA1ZZ for sending me this. 

The Importance to Bell Labs of Lunch or Breakfast with Harry Nyquist -- "The Communicator" -- Bimonthly Publication of the Surrey (British Columbia) ARC.

This is a good sample (!) of the great content to be found in "The Communicator." This is the bimonthly publication of the Surrey (British Columbia) Amateur Radio Club.  You can find the publication and digital back issues here: https://ve7sar.blogspot.com/ 

There is a lot of great material in this publication. 

Pete N6QW Has Hybrid Rig On-The-Air

 

A thing of beauty on a wooden board.  Pete's post: 

https://n6qw.blogspot.com/2024/11/11252024-1st-dx-with-40m-hybrid-rig.html

"Them that know can make it go!"  Indeed.  

Pete talked about the history of this rig, and especially of the Thermatron portion of it, in the most recent episode of the SolderSmoke podcast: 

https://soldersmoke.blogspot.com/2024/11/soldersmoke-254-audi-and-video-versions.html

Thanks Pete! 

Oscar 7... and Oscar 11 (aka UoSat-2)? Did Oscar 11 do much the same thing as Oscar 7?

Above is a pretty good video by Retro Rockets.  Some will quibble about the technical details presented, especially about early radio, but I think the video does a pretty good job of describing the early production of ham radio satellites.  

As I watched this video however, I started to wonder if OSCAR 7 was in fact unique in coming back from the dead.  Back in 2018, I watched signals from OSCAR 11 (aka UoSat -2) as it tumbled through space with its battery dead, powered by a direct connection to its solar  panels: 

https://soldersmoke.blogspot.com/2018/12/ghost-ship-oscar-11-tumbles-through.html  

This was what Retro Rocket said was Oscar 7's claim to fame, right?  

In both cases, what happened was pretty cool, but did OSCAR 11 sort of repeat the supposedly miraculous rebirth of OSCAR 7?   

Sam WN5C uses ChatGPT as an Emergency Elmer

Sam WN5C has been on the blog before.  Last year we covered his heroic use of a Michigan Mighty Mite at Thunderbird State Park:  https://soldersmoke.blogspot.com/2023/06/sam-wn5c-builds-michigan-mighty-mite.html

This time, Sam writes about a good  ham radio use for ChatGPT: 

Hope you’re doing well. Just a quick note: ChatGPT is turning out to be a great homebrewing tool for me.

My elmer has been swamped with family issues, so my basic questions (“can you explain this circuit for me”) and hard questions (“why doesn’t this circuit I built work?!”) that he usually responds to right away has been a bit delayed. I’m in the process of designing a 5-band QRP CW transceiver with a superhet receiver and SSB receive so I’m learning a bunch of new circuits.

 

I’ve hated the idea of AI as someone who writes a lot (it cheapens what I’ve spent my career trying to perfect!), but man it is smart. I can ask it all kinds of questions. For example, it helped me design a little IF amp last night and ensured I got my impedance matching right (it’s great for mashing up lots of circuits and ensuring they work together). I can ask it for suggestions on part types and values. It helps with Arduino code if you’re into that. You can use plain language but it does well with heavy jargon. And, which I find really cool, it will step you through troubleshooting. It teaches the math, too.

 

Anyway, you or your readers might find this helpful. Especially when one is building at 3 AM and needs an answer immediately.

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

Thanks Sam! 

 

Tezukuri and Chappy Happy -- Amazing Videos on Homebrew Radio (from Japan?) - Another 40 Meter Direct Conversion Receiver

So around the time we were building 40 meter direct conversion receivers, someone else was doing something similar.  His product (above) is a lot nicer than ours.  He has an S-meter and a digital frequency readout.  But like ours, his is built on a wooden board.  FB OM.  

If you want to see what a direct conversion receiver can do, watch his video (above). 

I was really amazed to see him use a modified VFO from a Kenwood TS-820.  Not long ago Pete N6QW spotted one of these on e-bay and recommended that I buy it.  As with the Yaesu FT-101 VFOs, we bought it for the gears and reduction drives but ended up with the entire VFO circuit.  I now have one on my shelf, ready to go.  TRGHS. 

We are not sure who Chappy Happy is, but "Tezukuri" means "hand-made" in Japanese. The writing in the video descriptions are in Japanese, then Chinese. 

Here is the YouTube channel.  Amazing stuff here:  https://www.youtube.com/@chappyhappy3675  He is clearly a ham.  He even works on an old S-38.  Who is this guy? 

Basic Radio Circuitry -- a 1971 film

This 1971 training film is pretty good.  I like how they break the RF circuitry into just four components, then describe the AM receiver stage by stage.  The way they handle diode (envelope) detection is exactly right.  But their description of how mixing moves the incoming signal from the broadcast band to the IF is overly simple, and sort of just repeats the hetrodyne story from music. Real mixing is, of course, more complicated than that, but too complicated for a 15 minute film. 

Bill N2CQR Appears as a Guest on the Ham Radio Workbench Podcast

https://www.hamradioworkbench.com/podcast/hrwb-223-a-conversation-with-bill-meara-n2cqr-from-the-soldersmoke-podcast 

Partly in an effort to make ammends for some overly harsh comments I made about the podcast's approach to the "rejuvenation" of old radios (it turned out to be overly digital for me) I appeared earlier this month on the Ham Radio Workbench podcast.  It was a lot of fun. They are a great  bunch of guys.  And I think we had a great discussion of homebrewing and HDR in the modern era. We talked about Jean Shepherd, Farhan, G-QRP, kits vs. homebrew, homebrew vs. commercial, SDR rigs, the sBITX, the NORCAL 40, the Gilbert Cell Mixer, our experience (bad) trying to get high school kids to build a DC receiver, and many other topics. 

Thanks George!  And thanks to the entire Ham Radio Workbench crew!

Remember, SolderSmoke has issued a challenge to the HRWB team:  We challenge them to build the 40 meter Direct Conversion receiver that we designed for our local high school.  We urged them to build it the way we designed it -- avoid the temptation to substitute stages, or use pre-fab circuit boards.  Build the four stages Manhattan style and get the receiver working on 40.  Here are the details on how we did it.  Here are our building documents:

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

The challenge has been issued.  The gauntlet is on the ground.  Go for it HRWB!  Put those workbenches to use! 

Video -- Mythbuster II Rig Gets a Front Panel -- Circuit Build Almost Done

Yesterday I built a front panel for my Mythbuster II 20 meter SSB transceiver. 

I used 1/8 inch plywood available from Amazon. 

I cut holes for the main tuning knob and dial, for the AF gain control, for the mic plug and for a 6 figure PLJ PIC frequency counter.   This gives me 100 Hz read capability, but I can hit the lower button on the counter to get 10 Hz reolution.  This may help when the other guy complains bitterly that I am 40 Hz off frequency.  The counter added noise to the receiver, but I was able to knock this down completely with a resistor and a cap on the power line to the counter. 

I put copper tape on the inside of the panel. 

I added a reverse polarity protection circuit.  I now sleep more soundly. 

I increased the size of the heat sink on my RD06 final.  This decrease the danger of blowing up this device. 

I added a jack for the connector that will switch the outboard .1 kW linear from R to T.  

Video above. Comments welcome.  

 

FDIM 2024 Interview with Farhan VU2ESE

Thanks to Bob Crane W8SX we have some great interviews with those who made presentations at the Four Days in May event (FDIM 2024).  Sorry for the long delay -- it is all my fault, but I have excuses.  Our thanks to Bob W8SX, our correspondent at the FDIM event.  

Here is the interview with our friend Farhan, VU2ESE, the ham who has brought so much homebrew goodness to the hobby, starting years ago with the BITX 20 schematic. 

http://soldersmoke.com/FarhanVU2ESE.mp3

Thanks Bob!  Thanks Farhan!