Doug AA0MS's FB SolderSmoke Direct Conversion Receiver: "This project has been a hoot!"

Doug built a really beautiful receiver, but reception was marred by a bad hum.  It was quickly determined that this was caused by a noisy "wall wart" located close by.  A re-location of the power supply remedied that,  and allowed Doug to pull in some really nice signals. 

Doug writes: 

Had a lot of fun doing this over the past couple of weeks. Not my first DC receiver build--I built a Neophyte Receiver from QST years ago--but this one was the most fun. Thanks Bill, Dean, and the whole DCR challenge community--I'm learning a lot in my old age!

I'm a retired pastor who's been fiddling with radio stuff since about 1991, and though I've been inactive for long periods of time, I've always enjoyed QRP and homebrewing (and I've built a bunch of kits, too, including my main rig, an Elecraft K2). It's been a while since I had a halfway decent antenna up, but that's in the works. As a boy I was at my dad's side in his modest shack whenever he was building or operating (he was K8LZO back in the day), and one day while listening to shortwave broadcasts during the first Gulf war, I tuned around and heard some CW signals and decided it was time to learn the code and get my license. Anyway, this project has been a hoot, and I so appreciate all of you and your generosity with your experiences and experiments and successes and failures. Thanks! 73, Doug, AA0MS

Congratulations Doug and welcome to the Hall of Fame.

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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

 

Ramakrishnan VU2JXN's FB SolderSmoke Direct Conversion Receiver: "Extremely thrilled! Hooked!"

This is a really important Hall of Fame entry for us.  This is our first completed SolderSmoke Direct Conversion Receiver from India (more will come).  

Most importantly, this receiver was built by our good friend Ramakrishnan VU2JXN (ex VU3RDD).  Ramakrishnan goes way back in SolderSmoke history.  He was the one who first suggested (in 2006!) that our podcast needed a blog to go with it.  This was the origin of the SolderSmoke Daily News.  A short time later we announced the birth of Ramakrishnan's daughter.  That same daughter now has her ham license and will build a second receiver with her dad.  

Ramakrishnan VU2JXN

The roots of this receiver are deep in India. When Dean and I first went to the local high school to talk about ham radio support, I carried with me a Direct Conversion Receiver inspired by Farhan VU2ESE.  In fact, that receiver had a picture of Farhan and quotes from him taped to the wooden base.  When Dean and I designed the receiver that we tried to build with the High School kids, we used an oscillator based on the DC receiver that Farhan was building with youngsters at Indian girl's schools.  That is the receiver design that we are using in this SolderSmoke Challenge. 

Ramakrishnan is in Bangalore now, which is where he built this receiver.  Ashish N6ASD is also there now, and is building a receiver. 

Ramakrishnan writes:  

This morning before I got ready to come to work, I got a few minutes 

to turn on the radio and catch the morning nets. Extremely thrilled to

 get this working. The PTO is very stable.

Needless to say, you folks convinced me to get back into homebrew
and you have hooked me into it with this project.

I am off to my ailing mother's place tonight. I don't have a station 

there, but I am carrying a copyof EMRFD with me (I have two!).

I want to listen with this receiver as you all always say 

and make simple modification to this receiver and improve it.

 
Again, couldn't turn off from it even though I am at work! The bug has
caught me.

Here is some more video of Ramakrishnan's receiver: 

Congratulations Ramakrishnan. Welcome to the Hall of Fame! 

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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

Wow! DOVAD and Doppler at White Sands Missile Range

EI7GL has a really interesting blog post about a VHF system used at White Sands to accurately track early rocket tests:  https://ei7gl.blogspot.com/2025/05/369-mhz-doppler-radar-antenna-at-white.html 

He has nice picture of the antenna.  The plaque has the interesting info: 

The plaque on display reads as follows...

"36.9 Megahertz Helix Antenna Doppler Velocity and Position (DOVAP)

Reference Transmitter Antenna

Developed during World War II by the Germans as part of a V-2 guidance and control system, DOVAP traced the course of a rocket using the Doppler Effect caused by a target moving relative to a ground transmitter and receiving stations.

Unlike radar, Dovap did not allow scientists to "see" the rocket on a screen. Instead, it sent up radio waves, which were received and rebroadcast back to earth by the rocket. The returned waves combined with the original ground broadcast and produced a musical tone which varied with the rocket's speed - the faster the rocket, the higher the pitch.

DOVAP data was extremely accurate: it could place a rocket's position at 100 miles up within 50 feet. It could collect data at the extreme altitudes of 100 to 300 miles. Dovap's disadvantage was that it took 3 to 4 weeks to reduce the data.

The antenna is a helix because of its physical and electronic characteristics. A helix is simple to construct and operate, provides necessary signal gain and directivity, and can be operated in several modes or polarizations.

The DOVAP system provided trajectory data and ground guidance for most of the early rocket systems: Corporal, Sergeant, Honest John, Little John, Redstone, and Aerobee Upper Atmosphere programs.

This particular antenna was built in the mid-1960s near C Station. Like much of the early instrumentation used here, it was designed and built at White Sands Missile Range.

Erected by White Sands Missile Range Museum. (Marker Number 06.099.)"

Building "Newt" for "The Lightning Code"

This is part of our "Other Kinds of Workshops" series.  Newt was a little Arduino-R/C robot built for a movie called "The Lightning Code," which apparently has something to do with Nikola Tesla.  

Thanks to Hack-A-Day for the heads up. 

I admit it. I am not 100% homebrew. I hang my head in shame.

Walter KA4KXX and Mike WN2A and I were recently talking about the degree to which we are 100% homebrew. Both these guys come a lot closer to this goal than I do.  Here is my assessment of my gear: 

I fall far from a state of 100% homebrew grace:  

-- I use commercial power supplies.  I justify this by saying that I could use batteries, and I wouldn't build them. 

-- I use a D-104 with a Tug-8 amp in the base.  I justify this by saying that I COULD homebrew a mic, but I'd just be using a commercial electret element. 

-- My .1 kW amplifier is from a CCI kit.  I find it hard to homebrew 100 watt amplifiers that do not oscillate. Kits make this a bit easier.  

-- I use a K4KIO Hex beam.  I had a homebrew MOXON, but that got destroyed by a Northeaster.  And I have to limit trips up to the roof. Like to zero. (I ask the gutter guy to do this.) 

-- I have a DX-100 and an HQ-100 that I use to check into the Old Military Radio Net on Saturday morning.  I had a DX-100 as a kid, and John Zaruba K2ZA later gave me his dad's DX-100.  That is the one I use. I picked up the Hammarlund HQ-100 in the Dominican Republic in 1993 and have been repairing it ever since.  It is not a great receiver, but it looks good atop the DX-100 and I have a sentimental attachment. 

-- I have an HT-37 and a Drake 2-B that I have had since I was 14 years old. I have a strong sentimental attachment to this gear.  I have worked on most of this old stuff.  

The three SSB dual banders that I am running are mostly homebrew.  The Mythbuster uses a VFO out of the Yaesu FT-101. The 17/12 rig has an LM386 AF Amp. The 15/10 rig has an SBL-1. 

I will try to increase my HB percentage. 

"Unlocking the secrets of the heavens with a tool fashioned by one's own hand."

 

Click on the image for a clearer view. 

https://stellafane.org/tm/atm/

This quote is obviously about telescopes, but I think in many ways it applies to homebrew radio.   We sometimes use the term "first light"  to describe the first signals heard through a new homebrew receiver.  That term comes from astronomy, and is used to describe the first light seen through a new telescope.  I think there are strong parallels with homebrew radio.  

John KN6FVK's FB Homebrew SolderSmoke Direct Conversion Receiver -- Crickets Killed with Barkhausen-Be-Gone Spray!

I went to bed worrying about this one. John KN6FVK had been having a lot of problems.  He had repeatedly reported hearing nothing (crickets!) when he fired up the receiver. Members of the Discord group had provided a lot of coaching, but still, CRICKETS!  John had a good sense of humor.  When I pointed out that oscillations in the AF amp are caused by a feedback path that meets "the Barkhausen criteria" John said he went to Lowes and bought a spray can of Barkhausen-Be-Gone.  It seems to have worked.  Actually I think John put some additional capacitance on the DC rail of the AF amp.  In any case, he was going to wait for the evening for test out the fixed receiver.  The time difference with California meant that I went to bed with fingers crossed.  Happily the BBG spray and (more likely) the extra capacitance worked.  John sent us some really nice videos of his receiver in action.  I really like the inscriptions on his pine board.  This should become "a thing."   

John writes:

I'm very ok now.... --- sigh / smile --- THANK YOU ALL for your help and patience. As painful as this was, it was a lot of fun and I learned a lot. After I build an actual work bench, I might try this again (looks are important). But I'm definitely going to start playing with it and learning from it. On to Mods and Upgrades! Need to learn-up on this "Barkhausen" silliness too. -73

Here is John's receiver pulling in CW (WB6CGJ):

Congratulations John,  Welcome to the Hall of Fame.  

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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

Alan Wolke W2AEW's FB Homebrew SolderSmoke Direct Conversion Receiver

It is really and honor to have Alan Wolke W2AEW build one of our receivers.  Alan is a true wizard. Armed with an amazingly popular YouTube channel, he has taught electronics and ham radio to thousands of grateful viewers worldwide.  A Field RF Application Engineer for Tektronix, Alan has a special knack for showing us how to get the most out of our test gear.  

So many times have I gone back to videos that Alan made years ago, just in an effort to refresh my memory on the insights that he shared.  For example, it was from him that we learned how the diode ring mixer really works -- what it really means to say that this mixer multiplies signals by 1 and -1.  Alan even showed us how to get our 'scopes to display the multiplication.  This was all very cool and very typical of Alan's work.  His videos have been an important reference for this direct conversion receiver effort.  

On this project, Alan dug into his junk box, only to discover to his dismay that he didn't have the AF transformer that we recommended.  I am sure that Alan could have whipped up several alternative circuits that did not require the transformer, but he wanted to build the receiver the way we recommended, so a slight delay took place while Mouser filled his order. 

Alan did build the circut modularly, stage-by-stage, using the Manhattan method, but he admits to giving in to his temptation to use a very  small board.  This may be the most compact of our 60+ DC  receivers.  In an encouraging reminder that even the great ones worry about unwanted feedback,   Alan writes:

Why am I always compelled to build as compactly as possible?  I hope feedback doesn’t bite me in the butt!

Thank you Alan!  And welcome to the Hall of Fame! 

(This picture was created by displaying NTSC video from my digital camera on Alan's old Tektronix 485 oscilloscope using a simple converter circuit that is described in a video on my YouTube page)

QR code for his YouTube site

X Y Screen

On the SolderSmoke Blog there are 41 posts tagged with "Wolke--Alan": 

https://soldersmoke.blogspot.com/search/label/wolke%20--%20Alan

Alan's QRZ page: 

https://www.qrz.com/db/W2AEW

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

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

Phil W1PJE's Amazing MIT SolderSmoke Direct Conversion Receiver

 We are really pleased to see that Phil W1PJE has completed his direct conversion receiver and has thus joined the Hall of Fame.  Congratulations Phil. 

We are shamelessly calling this the "MIT receiver."  But the truth is that Phil's job at MIT was not part of this project, and in fact distracted him from his radio building efforts.  There was, however, one moment in which Phil had sent us a video of his receiver in progress.  There was some audible fan noise in the background.  Phil apologized, noting that the noise came from a nearby receiver that monitors upper atmosphere winds using meteors.  Now that, my friends, is some cool MIT stuff.  

Phil writes: 

Hi Bill and Dean,

  After a long hiatus (and a restrung antenna), I'm happy to report the Soldersmoke DC receiver is finally done and working well.  The relatively long video above shows a tour from CW to SSB to AM to digital telemetry to time signal (CHU at 7.850 MHz).  A bonus frequency counter was included to show the viewers where I was in the band.  It's not pretty but it works.  I need to slow down the tuning but that is a future job.   Sorry for the serious wobbly attempts to zero beat the AM carriers but I can fix that later...  hmm.

  Thanks for the fun and reminding me of a time when I was an undergrad at the EE bench.  Modifications are next when I can find a few minutes.

73

Phil W1PJE

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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

The Hall of Fame: 71 Direct Conversion Receivers Completed (so far) with 7 Honorable Mentions. More coming. Update.

Dean KK4DAS's Receiver

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 May 19, 2025  1717Z:

So far 71 completed receivers, with 7 honorable mentions:  

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

W8UC             Never before homebrewed. 

VK4PG           Phil -- Nice case, "really pleased"

G7LQX           Working well, video of CW and SSB. 

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.    

KF8BOG          Jim:  A long struggle, but success.  

Chris Wales    Fantastic video.  

YD9BAX        Wayan! Homebrew transformer! 

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

K1OA               Scott "Most fun in 50 years"

KC9DLM         Ben -- Had EFHW problems

PH2LB             Lex  Yellow, Glue Stick

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

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

AA0MS            Doug 

9V1/KM7ABZ   Paul in Singapore

VK2BLQ          Stephen

N3FJZ              Rick

Daniel               VE5DLD

Student 1          Student of VE5DLD

Student 2          Student of VE5DLD

Student 3         Student of VE5DLD

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

Honorable Mentions: 

*AA7U            Steve No PTO

*VK7IAN        Ian -- No Manhattan boards 

*KC1FSZ        Bruce's build on a PC board

*CT7AXD       Graham -- different AF amp

* DL1AJG      Andreas 

* Student 1     Student of DL1AJG

* Student 2     Student of DL1AJG 

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

Candidates for the Hall of Fame: 

SA5RJS              Rasmus

KA9TII               James

AA7FO              Chuck 

K7WXW            Bill 

VA3ZOT           Tony  Surface Mount -- Honorable Mention? 

KM5Z              Mike Yancey

AB2XT             John (Done, just need the video)

KO7M              Jeff (Piper Cub)

KD4PBJ           Chris

VU2TUM         Puneit Singh

N6ASD             Ashish in Bangalore

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

Louis W0IT Completes a Very Long-Term Goal and Finishes His Direct Conversion Receiver

Louis W0IT did what true homebrewers often have to do:  he persevered in an effort to make his machine work.  And he succeeded.  Congratulations Louis. Welcome to the Hall of Fame. 

Louis writes: 

I rebuilt all the boards, new components except the band pass filter and the mica caps, all which looked to be working up to spec. I bought the squares as they are smaller than the ones I made and while harder in someways they kept the mess down. I bought some J310's from Mouser and either the ones I had were less than optimal or I fixed something in the resolder. I ended up with 4 batches of those. They all tested different and the Mouser sourced ones had the lowest Vg (turn on voltage?) according to my 12$ tester at 1.65 V rather than 2.35 or 2.65 for the Amazon ones. The noise on it sounds almost identical to the noise on my Kenwood on the same antenna. Thanks Everyone. It's part of a very long term goal.

A very nice post about ham radio in Thailand by Louis: 

https://louiskatz.net/wpt/

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

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

Curiosity Rover on Mars as Seen from Orbit

The image was captured on February 28, 2025 by the orbiter’s HiRISE (High-Resolution Imaging Science Experiment) camera, and shows Curiosity’s movement over 11 drives starting at the beginning of that month. While a few weeks might seem like a long time for tire tracks to stick around in the dirt, this is normal for Mars. The tracks are “[l]ikely to last for months before being erased by wind,” NASA says. Curiosity is expected to reach its next science destination, which is home to formations thought to have been created long ago by groundwater, in the coming weeks.