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!  

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. 

 

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

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!

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: 

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

Brian KI7LKB's FB Modifications to the SolderSmoke Direct Conversion Receiver

 

Although we had strongly suggested that builders FIRST build the receiver in accorandance with Dean KK4DAS's excellent videos, we also told builders that once they got those receivers working, there was, of course, no limit on the modifications and circuit changes they could make. We are very pleased that Brian KI7KLB has followed this advice.

Brian writes:

The KI7LKB DCR has been modified to include the KK4DAS 3rd stage of the audio amp, a QRP guys frequency counter, and an enclosure made from scrap aircraft aluminum and hardware. My favorite mod, however, is the WB6AMT (SK and former Elmer) voltage regulator circuit. It allows me to power the DCR from the shack 13.8 volt power supply while simultaneously providing 9.5 volts for the radio and 12 volts for the frequency counter. While I ordered components from Digi-Key, it was fun to include a coat hangar, spare aircraft hardware, scrap wood, and repurpose the frequency counter from another project.

Grant K0GDB's FB SolderSmoke Direct Conversion Receiver

Congratulations to Grant K0GDB on his FB SolderSmoke Direct Conversion receiver.  Welcome to the Hall of Fame Grant! That PTO former is especially FB!  Grant is a relatively new ham, making his smooth construction of this receiver even more admirable. 

Grant writes: 

Proof of life video! Many thanks for the helpful YouTube tutorials, everything went together pretty smoothly.

The windings are actually as close to the specification as I could get them on the nanoVNA. It's been a bit since I built that part, but if memory serves I had one fewer turn and had to do some bunching to get it to read correctly. The main difference in the PTO is that I made the former on a laser cutter from slices of quarter-inch plywood since I don't have a 3d printer. The center cyllinder is actually just rolled up paper.

Bill WA5DSS's FB SolderSmoke Direct Conversion Receiver

 

Bill WA5DSS built this beautiful receiver back in December 2024.  Somehow I failed to include him in our Hall of Fame.  Well, better late than never, right?   Please let me know if we have missed anyone else. 

I think it looks and sounds great, on both CW and SSB.   Note the Costa Rica station in there in the SSB portion of the recording.  

Back in December 2024, Bill wrote: 

Bill, Dean,
I forgot to send you a recording. This is what I recorded last night. I did not let it “warm up” so the stability is a little better after awhile. Also, I have a knob for tuning…just haven’t hacked off the head of the bolt yet.

I have put the receiver up for now. I am trying to get a Heathkit DX-60 on the air for New Years Eve Straight Key night. It’s the only time I attempt a straight key. Also I am amazed at how difficult it was to operate these old cw radios. No wonder I didn’t get many contacts back in the early sixties...

...This has been an interesting project for me. I have built many kits since becoming interested in electronics during the 1960s but this is the first time I have started with unetched boards. I think I prefer the “dead bug” style over Manhattan. I don’t have the patience to plan out where all those islands go! 

Bill WA5DSS

Joe N90K's FB SolderSmoke Direct Conversion Receiver

Congratulations to Joe N9OK on his homebrew build of the SolderSmoke direct conversion receiver. Welcome to the Hall of Fame Joe.  

Joe makes some very nice comments on the benefits of doing this in a homebrew way:  

I've build many dozens kits over the years, esp Knight, Heath, K2, K3, and others. This was my first receiver built from scratch. It works surprisingly well and has decent sensitivity. Thanks @Bill N2CQR and Dean @Soldersmoke for creating this challenge. It was fun and non-trivial. The only stage I had issues with was the amplifier, which was too compact on v1. v2 works well.

I think Joe should hold onto that smaller version of the AF amp. I think he could get that stablized and it could become the heart of yet another FB DC RX.

Joe went the extra mile and measured the minimum discernible signal of the receiver:

 

I see no problem with Joe's measurment technique.  I think the key word here is "discernible."  Often people will focus on the RF signal that will produce a 3 db or 10 db increase in audio signal.  But Joe has just looked at the RF signal level that will create a discernible audio signal.  That is fine.  As Joe demonstrates, this simple DC receiver is remarkably sensitive.  

The Red-Shifted Neutral Hydrogen Signal from the Cosmic Dark Ages is in the Range of our Direct Conversion Receiver

On the flight to the Dominican Republic I was listening to Fraser Cain's interview with Dr. Christiaan Brinkerink.   I was kind of blown away when they started talking about where the neutral Hydrogen signal would be NOW, after the all of the cosmological red shift.  Asked this question, Christiaan kind of casually responds that it would be "just above 7 MHz."  He talks about this at 41 minutes and 41 seconds in the video above.  He points out that this represents a redshift of about 200.   Wow, that is just where our SolderSmoke Direct Conversion receivers tune, and where their PTO/VFOs operate.  And we thought Radio Marti was a factor to consider!   No wonder Christiaan and his colleagues want to go to the far-side of the moon.  They want to get above the ionosphere, but they also want to get the shielding provided by the moon to protect them, I suppose, from signals like those being produced by the 40 meter ham band, and, (to a lesser extent) by devices like our little oscillator. 

You can watch Fraser's interview with Christiaan above.  It is really interesting and inspirational.  Christiaan talks about dipole arrays, RFI, interferometers, sensitivity, signals of "several kHz" in width, dynamic range, and other topics known to us.  Christiaan is an "Instrument Systems Engineer" at Radboud University.  I think he deserves a ham radio license.  Maybe he should build a SolderSmoke Direct Conversion receiver.  Fraser should build one too.  

Here are a couple of links to articles about this: 

https://www.universetoday.com/articles/observing-the-dark-ages-of-the-universe-from-the-far-side-of-the-moon

https://pmc.ncbi.nlm.nih.gov/articles/PMC10961189/

Thank you Fraser and Christiaan. 

Fritz's FB SolderSmoke Direct Conversion Receiver

Fritz did an excellent job on his build of the SolderSmoke Direct Conversion receiver.  Fritz writes: 

Hi folks!  First-time radio builder here, and I've just completed my DCR build! (Pic and video below...)

I have a background in electronics, but mostly audio, digital, video games, tube guitar amps, etc.  My only previous experience with radio was a restoration of a small AA5-style radio for a friend.  I first saw this project featured on w2aew's site and it seemed too fun not to try.  First go with Manhattan construction, too, and I really enjoyed it!

Though I built everything on one board, I did test the modules one by one as I went.  I did build and test the audio amp "left to right" instead of the other way around, because I have enough bench gear that I could check as I went without relying on the speaker. 

My audio amp build did tend to motorboat turned about half-way up, particularly with no RF input.  It was easy to see on the 'scope that the DC power bus was the feedback path.  Threw a couple 470uF on there and that pretty well quenched it.  In addition to the coil former, I also 3d printed a battery clip and and bracket for the volume pot.

Tuning turned out to be pretty delicate/twitchy, but I am getting better at it.  I opted to start with the 28 TPI steel screw after reading some things on the blog.  I will probably end up moving some of the windings off the tuning former to try and improve this, and/or investigate a fine tuning option.

I am running right now with a 33' wire out my basement window, up the side of the house, and partway across my flat roof, plus a 16' counterpoise on the basement floor.  Will probably get more ambitious with a feedline to a vertical wire in a tall tree in the backyard away from the house this upcoming week.

No license or callsign yet, but I've definitely got the bug with this project, so am reading the materials and hope to take the exam(s) soon!

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

Congratulations Frtiz -- Welcome to the Hall of Fame! 

Dan KF5DAN's FB SolderSmoke Direct Conversion Receiver

It is a happy occassion whenever we get to announce a new member of the SolderSmoke Direct Conversion Receiver Hall of Fame.  And Dan KF5DAN has entered the hallowed halls.   Congratulations Dan.  We are really glad you are doing the happy dance.   Above you can see Dan's receiver inhaling SSB, in the video below you see it receiving CW. 

Dan writes: 

I would like to present proof of life! I found the motorboating issue in my amplifier. R18, 1K resistor was connected from the power rail to the base of Q5, instead of the collector. I moved it, and had already added a 470uF cap from earlier troubleshooting. There is a lot of noise, probably due to some stormy weather in Arkansas this evening. I'm doing the happy dance over here.

Thank you very much! I am very appreciative of all the guidance and suggestions everyone has provided. I am very happy to be in this group of hams and homebrewers.

Alan W2AEW Measures the Minimum Discernible Signal (MDS) of the SolderSmoke Direct Conversion Receiver

So cool that Alan did this.  Here we see a rigrourous measurement of the MDS of our receiver, with a correction for the bandwidth.  Very nice. 

It can discern signals down to -125 dbm.  I think that is pretty good for simple receiver like this.  

Alan agrees that another way to do the sensitivity test is to just listen for the band noise when you connect and disconnect the antenna.  Especially on the low HF bands,  if you can hear it, you have sort of maxed out on receiver sensitivity.  

Thanks Alan!