GQRP Convention 2025 -- SolderSmoke Direct Conversion Receiver Presentation

We were really pleased to have been invited to speak to the GQRP club's 2025 convention.  We talked about the SolderSmoke Direct Conversion Receiver project.  There were some recording glitches, but we managed to re-create the presentation.  Video appears above.  Thanks again to GQRP!  

Here is the audio only (podcast) version:  http://soldersmoke.com/DCRXGQRPAUDIO.mp3

Flying in the U-2

So cool.  This was always one of my favorite planes.  

So hey, BE CAREFUL!

 

The vessel "Tally Ho" sailed into San Francisco bay recently.  They went to a very cool machine shop in Sausalito, where they found this warning sign posted near one of the machines.  Yikes! 

Here is the Tally Ho video:  https://www.youtube.com/watch?v=yHf9K_dOgsY&t=422s

Todd W2TEF's FB SolderSmoke Direct Conversion Receiver

 

Admirably, Todd W2TEF proved that you can build this receiver even if you don't have an oscilloscope. He used a lot of simple tests, including listening for the band noise when he had all four boards finished. He got the kind of help from friends that all of us use while homebrewing.  And he tuned in SSB signals for the first time.  FB.  SSB in the video above, CW below. 

Todd writes: 

1. ... thanks to Dean and Bill for putting this together and guiding me into a great beginning project. And to Chris and others offering guidance here in Discord. I love seeing a project through to completion, and am still amazed that twisted up coils of wire can grab intelligence out of the air!

The People Who Hunt Old TVs (Really, Old CRTs)

These are our people. 

 https://www.bbc.com/future/article/20250911-the-people-who-hunt-down-old-tvs

50 Things to Do with an SDR -- The International Beacon Network

 https://blinry.org/50-things-with-sdr/

Lots of good ideas from blinry's site.  It reminded me of the International Beacon Project:  https://www.ncdxf.org/beacon/  I can receive the 20 meter CW signal on my homebrew rig here in the Dominican Republic.  On 17 September before dawn I could hear the station in Madeira (CS3B) and the one at the UN in New York (4U1UN).  This will be a useful way to monitor the band for openings to the South Pacific. 

Hiding a Solar-Powered Mesh Node in Alaska -- Can you find it?

 Even though it deals with some high-tech, SDR, IC stuff, there is a lot to like in this video. 

Some of the guys in Vienna Wireless have been playing around with Mesh nodes.  This video made me think about building one and leaving it on the roof of our apartment overlooking the Mona passage. I already have the solar panels (from the old Volkswagens)...  

Here is a description of his YouTube channel: 

A collection of DIY boats, devices, and other projects built out of junk. Almost everything on this channel is made from scrounged, hoarded, and salvaged parts. I grew up on an island in Alaska, so I know the value of never throwing anything away! I may not be an expert craftsman, but I know my way around a roll of duct tape! I'm also always on the lookout for crazy free or cheap stuff, whether it be electronic parts, boats, aircraft engines, or even a monorail train! Check out www.saveitforparts.com for even more projects!

Here is the YouTube channel: https://www.youtube.com/@saveitforparts

Thanks to Jenny List of Hack-A-Day for alerting me to this. 

A Flight from Chile to Panama: Aeronautical Mobile Contact with KX4WC/AM, with VK3MO in the Group

WA3O sent me an e-mail alerting me to the fact that Mike KX4WC/Aeronautical Mobile would be flying up from Santiago, Chile to Panama City this morning. So I fired up the 20 meter rig and hoped for the best.

Not only was I able to talk to Mike, I was also able to work WA3O, VY2WW, and VK3MO in Melbourne. It was a very FB morning. VK3MO was really booming in. I have worked Ian before -- his 5 over 5 over 5 over 5 array on 20 meters really helps. https://www.qrz.com/db/VK3MO

I was not hearing Mike KX4WC very well until the sun came up over our north-south path. You can see this in the picture below. Thanks to all for this very cool contact.

Ian VK3MO's 20 meter array

Peter VK3TPM had done a very nice profile of Ian and his station: 

https://www.mrarc.org.au/member-profile-ian-vk3mo/

Do I really NEED Tropo to hear the Puerto Rican FM Broadcast Station? Or are we just close enough to do this line-of-site?

 

WIDI 99.5 FM from western Puerto Rico continues to put a full quieting signal into the eastern Dominican Republic.   The station is so regularly strong that this made me wonder if I am really using tropospheric ducting to hear it.  If I was using tropo ducting, I think there should be some variation in signal strength over the course of 24 hours right?  But it is always strong.  Why?  

I checked the distance:  97 miles.   With its antenna at 2800 feet, its visual horizon will be 64.8 miles away.  I am about 98 feet above the ocean.  This means my horizon is 12.22 miles away.  There appears to be a gap, right?  I mean 64.8 + 12.22 = 77.02 miles.   So it looks like there is a gap of about 20 miles.  

But wait!  Mike WN2A reminded me that there is a difference between radio line of sight and visual line of sight.   Radio line of sight = 4/3 of visual line of sight. 

AI explains where the 4/3 factor comes from: 

The radio horizon appears longer than the visual horizon by a factor of about 4/3 due to atmospheric refraction, which bends radio waves slightly downward. To simplify calculations, this effect is modeled by treating radio waves as if they travel in a straight line over a larger, "effective" Earth with a radius 4/3 times the actual radius. This increased effective radius allows radio waves to "see" further over the Earth's curvature, extending the line-of-sight range compared to what is seen by the human eye, which is not affected by atmospheric bending to the same degree. 

So that puts WIDI's radio horizon at 86.4 miles.  My radio horizon is 16.16 miles.   86.4 + 16.16 =  102.56 miles No gap.  We should be able to hear WIDI, even without tropospheric ducting.   

Philippe F1GMA's Fantastic SolderSmoke Direct Conversion Receiver

SSB

Wow, congratulations to Philippe F1GMA for his wonderful build of the SolderSmoke Direct Conversion Receiver. Phillipe deserves extra credit for achieving this goal while working in a foreign language, and with parts acquisition even more of a challenge for him.  That AF transformer was hard to get in France.  And I see that a companion CW transmitter may be in the works.  FB.

The SSB signal that Philippe provides includes a clip from special event station TM120ESP.  That station commemorates the 120th anniversary of the first Esperanto congress.  FB.  TRGHS! 

Congratulations Philippe and welcome to the Hall of Fame.  I think you are our very first French builder.  

Click here for a CW clip

Puerto Rico -- Dominican Republic Tropo on 99.5 FM? Yes, probably

 

Our friend Todd K7TFC in Portland found this in the 1950 ARRL Handbook at an, uh, opportune moment.  TRGHS.  This seems to describe what a I am hearing, especially that "airmass boundary" in the lower left of the diagram above.  

I'm not a VHF guy, and I am a bit surprised at the persistence of this propagation path.  It is 4:30 am here and the adult contemporary rock from Puerto Rico (Kokomo by the Beach Boys!) is full quieting here in the Dominican Republic.  And it is of the same strength during daylight hours. I don't remember this from the winter months, but I may have just missed it. 

Here is what AI (Gemini) says about this: 

https://share.google/aimode/M1HvC7Y893eE5gAcn\

One other factor to consider:   The island of Mona is about halfway across the path.  There are few people there, and there is almost certainly not a repeater of any kind.  But there may be a metal tower or two... 

Gianfranco IU1DZZ and Mike WN2A  both support the tropo hypothesis.  Mike mentions the Hepburn Index.  I will have to read up on that.  Hamilton is also looking at this propagation path.  Thanks guys.  

Puerto Rico FM Broadcast Station Heard in the Dominican Republic -- But How? WIDI 99.5 FM

WIDI 99.5 FM. Booming in during daylight here on the eastern tip of the Dominican Republic. Their antenna is about 2100 feet above average surrounding terrain. That would put the horizon at about 56 miles. But the path is about 100 miles. What do you folks think is the likely propagation mode?

https://en.wikipedia.org/wiki/WIDI

Chris KN4GAH's 100th! SolderSmoke Direct Conversion Receiver

This was the 100th SolderSmoke receiver!     It was really cool to see Chris KN4GAH's  receiver inhaling CW (sbove)  and SSB (below).  I especially like the ink pen markings on the pine board.  FB.  Maybe make note of memorable QSOs heard, or -- later -- contacts made with this receiver.  

Chris is an electrical engineer, so it was particularly useful for us to get his perspective on this project.  We started this at the High School knowing full well that most of the students would spend their careers in the high tech, digital world, and might never again touch a soldering iron.  But we thought it would be good for them to build something like this at least once.  Chris comments on this idea below.  

Chris writes: 

Thank you for putting this all together for all of us and creating such a great community full of knowledgeable and helpful people. I work as an RF engineer and mentor a few junior RF engineers and will be proposing this challenge to them as a learning opportunity. As this challenge provides a lot of insight into how common blocks used in RF designs operate. It is just too easy to go on mini-circuits and find a filter, amp or mixer that meets ones needs. Actually building these components provides valuable knowledge that all us RF engineers should have.

Thanks Chris, Congratulations and welcome to the Hall of Fame!

Chris KD4PBJ's FB SolderSmoke Direct Conversion Receiver

Chris KD4PBJ is one of SolderSmoke's most loyal fans.  Over the years Chris has supplied many of the parts and ideas used in SolderSmoke projects.  We were really delighted when Chris took on the Direct Conversion challenge.  As you can see,  his build was superb. 

Chris had promissed to have the receiver completed by September 2, 2025.  As it happens, that was the day of some very powerful solar activity and very poor band conditions.  So the video above doesn't really do justice to Chris's receiver.   We hope he will send us some more video, perhaps under better conditions, and perhaps with some more SSB. 

As you can see from this message from Chris in mid-July, he is a busy guy.  We were pleased that he found time to build this receiver.  Chris wrote

Good Morning guys!
I spent my July 4 weekend and 1200 round trip miles heading up to Richmond to pick up two 50 watt decommissioned airport non directional beacons that I hope to get working on either the 630m or 2200m bands. I'll most likely just use the amplifier, power supply and matching sections as they are modulated CW which isn't permitted. 
At least I have a nice high current power supply, outdoor enclosure and inner workings. I was told one worked and one doesn't.
I got them off eBay and the seller is a television engineer in Richmond named Greg. He listens to Soldersmoke too and is a builder like I am.
He said these are government surplus from a place called Camp Peary in VA.

The DC receiver is still coming along, I've just been overwhelmed with things on my to do list as well as a new job (learning lots about  high power lasers) so I promise it will get done soon. 

Chris 

Here are a couple of pictures of Chris's receiver.  Thanks Chris, and Welcome to the Hall of Fame.     

 

Dave K5YFO's FB Texas SolderSmoke Direct Conversion Receiver

The pine board is key.  Frank Jones (W6AJF) would approve. FB Dave.    CW video above and SSB below. 

Dave writes:  

Bill,

After many diversions from the work bench I finally got the Solder Smoke Challenge Receiver to operate.  There were the usual problems with the audio amp but my main problem was a faulty trimmer in the BP filter.

 

I hope I’m in the first 100 to complete the project. 

 

Hopefully the attached videos make it.  One is a CW and the other is SSB. 

 

73 de Dave K5YFO

Robert Sutton's Amazing SolderSmoke Direct Conversion Receiver

It is amazing that Robert (who is not yet licensed) got this receiver to work.  Check out his homebew coil form.  Excellent work Robert.  Congratulations and welcome to the Hall of Fame.  

Here is a Dicord exchange with Robert.  I think we see the true homebrew spirit here: 

Hall of Fame Update: 96 Completed SolderSmoke Direct Conversion Receivers, and 7 Honorable Mentions. Total: 103 receivers as of October 19, 2025 1649Z. More receivers are being built.

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 October 19, 2025 1649Z:

So far 96 completed receivers, and 7 honorable mentions.  Total Count:  103.       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

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

Honorable Mentions: 

*AA7U            Steve No PTO

*VK7IAN        Ian -- No Manhattan boards -- Tasmania

*KC1FSZ        Bruce's build on a PC board

*CT7AXD       Graham -- different AF amp -- Portugal

* DL1AJG      Andreas -- Germany

* Matthew      Student of DL1AJG

* Arash           Student of DL1AJG 

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

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)

VU2TUM         Puneit Singh

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

Bob K2BVR's FB SolderSmoke Direct Conversion Receiver

Bob K2BVR homebrewed a really nice SolderSmoke Direct Conversion receiver.  On his "Proof of Life" video we hear some nice SSB signals, some great CW signals (including N7DZ/6 POTA) and even the well-known tones of FT8.  FB Bob.  Congratulations OM!  Welcome to the Hall of Fame. 

Bob writes: 

Hi Bill,

I wanted to send you a quick note of thanks. I’m very grateful to the SolderSmoke Discord users for their help, and to you and KK4DAS for all of the work you’ve both done in developing this project and sharing it through your videos.

I’ve been making progress on my build and thought I’d share a little update. I ran into some challenges with the bandpass filter – it turns out that reducing the trifilar winds per inch helped improve the performance. I also fought with a shorted test fixture along the way, which made things more confusing than they should have been.

On the audio side, my first amplifier module is still giving me trouble. I hated not getting it fixed right away, but I’ll be coming back to it. I did have to add a 470uF cap to the power rail to control oscillation but I haven't added the 220 ohm resistor. I’m thinking about putting the different modules into their own boxes so that I can experiment with them more easily in the future.

Thanks again for all of the inspiration and guidance — I really appreciate it.

73s

K2BVR

 

Tobias KK7BCO's FB SolderSmoke Direct Conversion Receiver

Sounds great Tobias!   Congratulations -- Welcome to the Hall of Fame! 

Tobias writes: 

Bill, I have joined the few. 

You guys created a project that even I could build. Thank you for the journey!

Now I plan to make duplicates of some elements, and create some kind of a terrifying musical instrument. 

Perhaps a Theremin Tobias?  AKA Etherphone!  This was reportedly one of Neil Armstrong's favorites! 

https://en.wikipedia.org/wiki/Theremin

Shane G0JNR's FB SolderSmoke Direct Conversion Receiver -- With a Glow-In-The-Dark PTO Coil Form

I was really pleased to see Shane G0JNR finish this receiver. He has been an active member of the SolderSmoke community for many years.  For example, back in 2018 we see him commenting on KU4NO's FB rig: 

https://soldersmoke.blogspot.com/2018/07/a-rig-with-maximum-soul-5-band.html

Shane writes: 

Shane G0JNR here. I've just got my Soldersmoke DC rx up and running! The thing that put me off earlier in the year was the 3d printed coil former. But my son has now got one and printer and printed one for me - as an added bonus, it glows in the dark! It didn't work straight away but perseverance has paid off. 73

Thanks Shane! Congratulations and Welcome to the Hall of Fame.

Glow-In-The-Dark PTO Coil Form