Walter KA4KXX's Innovative 20-meter SolderSmoke Direct-Conversion Honorable-Mention Receiver

 

It is a thing of beauty.  We were really pleased to see our old friend Walter KA4KXX take on the SolderSmoke challenge, and we weren't a bit surprised to see him do so using some real twists in the design.  You see, Walter is a very experienced homebrewer.   He has built many, many rigs over the years.  Just check out his QRZ page and you will see what I mean: 

 https://www.qrz.com/db/KA4KXX

Walter supported our original high school effort by offering the students a $500 prize for any student who used our receiver (and a similar transmitter) to check in to the 40 meter Sunrise Net.  Sadly, there were no takers.  But we really appreciated the attempt. 

We have listed Walter's receiver in the Honorable Mention category, only because his build is so innovative:  20 meters instead of 40.  An IC in the audio amplifier.  There were differences, but even a quick look at the above picture above shows that Walter's receiver is very much a SolderSmoke Direct Conversion Receiver.  

Here are some additional photos from Walter. 

Congratulations Walter.  Welcome to the Hall of Fame!  

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From Walter's QRZ page

Dave Richards AA7EE Builds and Documents the SolderSmoke Direct Conversion Receiver

As always with Dave's builds, " 'tis a thing of beauty."  His photographs and documentation make it even better.   Please go directly to Dave's site and enjoy his look at the SolderSmoke HOMEBREW Direct Conversion Receiver:  

https://aa7ee.wordpress.com/2025/12/04/the-soldersmoke-direct-conversion-receiver/

Thanks Dave! 

Jay KI5VIR's FB Homebrew SolderSmoke Direct Conversion Receiver

Jay KI5VIR is a new ham, but you would never know this by looking at his build of the direct conversion receiver: It looks like something built by someone with a lot more time the amateur ranks. (See above.) 

Jay writes: 

I have completed the direct conversion reciever and I can't thank Bill, Dean and those that commented and asked questions on discord enough. This was my first build and I can't believe how much I learned. I have a long ways to go,  but this was just what I needed to get started in homebrewing.  1- (BIGGEST CHALLENGE)  was probably the diode ring mixer and learning to use my scope and setting it up to test the circuit. (this was also the most rewarding stage) 2-(WHAT DID YOU LEARN AND WHAT WAS YOUR BIGGEST CHALLENGE?) I got a basic understanding of how to read a circuit and what different components do in the circuit.(I still want to revisit each stage and make sure I get a little more) 3-(WHAT WOULD YOU LIKE TO HOMEBREW NEXT?) I want to first dissasemble each board and rebuild while it is fresh in my mind and make sure I get a little better understanding. After that, I want to either build a transmitter to go with this reciever, or build a complete transciever. Not sure whether to build ssb or cw, but I definately want to build something I can make at least a few contacts with. 

 Congratulations Jay, and welcome to the Hall of Fame! 

Dave AA7EE's Beautiful (Typically Beautiful) SolderSmoke Direct Conversion Receiver

Dave Richards AA7EE is justifiably famous in homebrew circles for the beautiful photographs of his rigs, and for the superb documentation of his builds.  You will see what I mean when you visit his blog: 

https://aa7ee.wordpress.com/   

We were very pleased when Dave told us he would build the direct conversion receiver that we have been discussing on Discord. 

Dave writes: 

Phew! Well this was a bit of a journey, and a slightly humbling experience. I looked at the schematic and thought, "Hey, I can build this. Shouldn't be too hard!" But the homebrew Gods judged that it was time to remind me of my place in the big scheme of things, by imbuing my receiver with in-band breakthrough from SSB, CW, and digi stations. Strong in-band stations within about 50KHz were breaking through and being heard in the same way that you'd hear SSB, CW, and digi signals on an AM receiver without a BFO. Their pitch wasn't changing as I tuned, because they had no pitch. Bill suggested that RF was getting into places it wasn't supposed to be, and being envelope detected by the AF amp. As it turned out, he was right. If anyone's interested, I can post a video of the issue I was experiencing. In the meantime though, I'll keep this post brief. I have quite a lot of pictures from various stages of the build, but posting them all here might be a bit TMI. I wanted to make this receiver reasonably compact and build all the stages on one board. My near-pathological tendency to try and build things fairly small could have contributed to the breakthrough problem that I experienced. I won't go into all the details of the troubleshooting process here, unless people are really interested, though I'll detail them in a post on my blog, as I think that sharing this stuff can be helpful to other builders - just as I have benefited greatly from others sharing with me. I made a few small changes from the original schematic, to cure the issues I was experiencing. Will detail them in another comment underneath, as the free version of Discord puts a character limit on posts.

I made the following small changes, to cure a couple of issues this little receiver was experiencing - 1) The AF amp was motorboating at anything above about medium volume, so I swapped out the 47µF capacitor in the +ve supply line to the AF amp (C10) for a 470µF part. This killed the motorboating dead in it's tracks. 2) To solve the in-band breakthrough issue, I did two things - a) At the suggestion of Peter VK3TPM, I placed a 1K resistor in the +ve supply line to the first AF amp stage, Q5, between C15 and R8. In conjunction with C15, this forms a lowpass filter with a 3dB cutoff point at about 3Hz. With a 12V supply, ~3.5V is dropped across this resistor and at 9V, the voltage drop is ~2.3V. If this voltage drop is too much for you, you can try a lower value of resistor and perhaps increasing the value of C15. This voltage drop does decrease the gain of the stage a little. In my case, it was welcome, as the amp was tipping over into feedback at full volume. Adding the resistor eliminated this, so I can now run the AF gain pot at full tilt. b) I added a 0.22µF capacitor from the wiper of the AF gain pot to ground, as an RF bypass. Physical placement of this cap was close to Q5. It also shapes the audio a little, cutting out some of the high-frequency hiss. You can experiment with different values here. I was initially going to use a 0.1µF part, but 0.22µF provided better protection. Greater values cut out too many of the higher frequencies for my liking. For a relatively simple receiver like this, I like the wide open sound.

I removed the spring from the tuning shaft. Tuning is smoother now, and free from backlash.

Dave 

AA7EE 

Here is a video of Dave's receiver inhaling CW during the CW Sweepstakes contest:

Here is one of Dave's iconic photos of the receiver:   

Thanks Dave!  Congratulations and welcome to the Hall of Fame!  

SolderSmoke Homebrew Direct Conversion Receiver Hall of Fame Update: 100 Completed + 7 Honorable Mentions: Total Receivers Built: 107 (As of January 1, 2026, 1400Z)

 Please let us know if you spot any errors, or if we have inadvertently missed anyone.  Don't worry about being late to the game -- the challenge continues.  All of the info is still available (see below). 

As of January 1, 2026 1400Z:

So far 100 completed receivers, and 7 honorable mentions.  Total Count:  107.       Receivers built in 17 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    

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

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

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!) 

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

W2DAB           Dave in NYC

W4JYK            Wes of VWS

KA4CDN          Mike of VWS

M7EFO             Adrian 

VK5RC             Rob

KD8KHP          Dave

VK1CHW         Chris

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

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

AA7EE             Dave Richards

KI5VIR            Jay

CT7AXD       Graham -- Promoted from Honorable Mention!

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

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

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

Candidates for the Hall of Fame: 

SA5RJS              Rasmus

KA9TII               James

AA7FO              Chuck 

VA3ZOT           Tony  Surface Mount -- Honorable Mention? 

AB2XT             John (Done, just need the video)

KO7M              Jeff (Piper Cub)

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

Join the discussion - SolderSmoke Discord Server:

https://discord.gg/Fu6B7yGxx2

 

Documentation on Hackaday:

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

 

SolderSmoke YouTube channel:

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

Puneit Singh VU2TUM's FB Homebrew 40 meter SolderSmoke Direct Conversion Receiver

It was really good to see Puneit Singh finish this receiver project.  He overcame many difficulties, including a lot of travel and an acute shortage of time, but he got it done. Congratulations Puneit Singh and welcome to the Hall of Fame. 

Puneit is also a CW man -- we hope he pairs this receiver up with a simple CW transmitter and makes some "fully homebrew" contacts. 

 

2025 ARRL Technical Service Award

 

Thanks to the ARRL for the award.  It is much appreciated.  Thanks too to all the people who built this receiver.  There are more than 100 of them and they come from all around the world.  We hope that they will go on to become homebrew Elmers, and help others to discover "the magic that emerges in a room full of solder smoke, and that only comes from a receiver that you have built yourself." 

And special thanks to Bruce KC1FSZ for nominating us for this award. 

Karl EI9ITB's FB SolderSmoke Direct Conversion Receiver -- First Receiver Built in Ireland

Congratulations to Karl EI9ITB for the successful completion of his SolderSmoke direct conversion receiver.  Above you can see Karl's receiver inhaling SSB on 40 meters.  We also got a nice CW video.