SolderSmoke Podcast #260 FDIM, Hollow State Design, Pete's Bench and the Shelf of Shame, Direct Conversion Project News, How Best to Preserve this Blog?, Dean's Bench and the Desk of Despair, Bill's Bench and the Garage of Grief, MAILBAG

SolderSmoke Podcast #260 is available: 

Audio version:  http://soldersmoke.com/soldersmoke260.mp3

Video version: https://www.youtube.com/watch?v=bZzHSjOTbSY

Quote from the Old Miltary Radio Net:  "Being on the leading edge is great, but sometimes being on the trailing edge is more fun."  Indeed. 

Heard from an Australian on the Southern Cross Net:  "My antenna needs a lot of Viagra!" 

News from Dayton/Xenia/FDIM: Dayton Xenia.   Again, we didn't go.  But Bob Crane W8SX was there and got a nice interview with Grayson,  Hans, and Farhan.  We are presenting these and more.  Michigan Mighty Mite Revival at FDIM!  Jeff W9TH. 

Farhan's review of Hollow State Design: I am compelled to set aside the future of my family and to orphan my cats to resume work on the 250v power supply that I built last year. Inshallah, Allah favors those who favor thermatrons!   Grayson's book is  imbued with deep experimental insights and littered with gems. You have to read it over and over to find new things each time.   It goes into my reference shelf in the lab."  Buy it here: https://www.ermag.com/product-category/books/ 

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PETE'S BENCH:

Pete working on JF3HZB dial.  Send Pete a Heath mono-bander! 

MHST on shelf of shame? Even the great ones have to take a break every so often. On the importance of taking a break. Ernest Rutherford 1917 and all that:  https://soldersmoke.blogspot.com/2025/05/on-importance-of-taking-break.html 

Channelized 40 meter rig. Heard in Arizona by Andy KB7ZUT on a HOMEBREW SSB Reciever.  Very rare.   SWL HB2HB. 

Pete:  Thumb broken as a Novice?  Early episode of Fat Finger Syndrome? 

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DC RX NEWS:  

Quote from N6QW:  "The radios do not build themselves!"  

Alan W2AEW finishes Direct Conversion Receiver. And even he worries about feedback! 

Phil W1PJE MIT receiver  (with cool MIT stuff).  Coming to see us! 

KN6FVK's Barkausen-Be-Gone Spray :https://soldersmoke.blogspot.com/2025/05/john-kn6fvks-fb-homebrew-soldersmoke.html

Indian hams working DC RX. VU2JXN Ramakrishnan, VU2TUM  Puneit Singh, Ashish N5ASD, building one in Bangalore with 3D printed form from Scott, KQ4AOP.  Ramakrishnan is planning on building a second receiver with his daughter. On June 22, 2008 in SolderSmoke #86 we reported on the birth of Ramakrishnan's daughter.  This is that same daughter! See: https://soldersmoke.blogspot.com/2024/01/long-time-soldersmoke-supporter.html    How to get a PTO form in India.  A tip from Ramakrishnan: "I got the 3d printing done via https://robu.in with 1:1 size. After uploading the stl, I received it by post in 5 days or so."

German students of Andreas DL1AJG.  and Canadian students of Daniel VE5DLD. 

Receiver built in Singapore!  9V1/KM7ABZ

John M0XJA reports 8 members of his club are building this receiver. 

Chuck N4AVC got his PTO coil form 3D printed at the local library. For free!  FB! 

Few admit to being fooled by April Fool story.  But still, inspirational. VK3HN was going for a few seconds -- SOTA AI chatbots? John West liked the 85th harmonic threat. 

What next after DC RX?  Choose carefully! Don't bite off more than you can chew. 

Do some mods!  Build something else!  And remember to be a homebrew Elmer.  Help someone else build the receiver. 

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SHAMELESS COMMERCE DIVISION: 

Check out the SolderSmoke blog on the WayBack Machine.  The blog, not the podcast.  www.soldersmoke.blogspot.com   Would this be a useful backup if Google were to pull the plug on blogspot?  Is the format OK?   Is the template recoverable?  How best should  we backup the SolderSmoke blog?  

Be a Patreon SolderSmoke Sponsor!   Please subscribe to the YouTube channel!  Buy your Amazon stuff through our link.  Buy stuff from Mostly DIY RF.  

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DEAN'S BENCH:

Dean has completed his Mythbuster: https://kk4das.blogspot.com/2025/05/kk4das-mb-20-transceiver-complete.html   Plexiglass top! 

Diode switching. 

Dean:  Build of the SDR receiver.  Microscope required? 

____________________

BILL'S BENCH:

VK6JDW and HCJB in the Kimberly. 

The stages of separation:  Shack, Garage, Car trunk:  HP-8640B and HAMEG scope saved from garage. HP-8640B repair.  HAMEG Modulation Monitor. 

=================

MAILBAG

-- Wouter ZS1KE.  Thinks Soviet spies COULD homebrew.  Hamilton KD0FNR concurs. Agent Sonya and Soviet Spy homebrew. Copacetic Flow. I dunno....I dunno... 

-- Hamilton KD0FNR grew up in New Mexico, supports my idea of Starlink deorbit. See : https://www.kallmorris.com/columns/goodness-gracious-green-balls-of-fire

-- Adam N0ZIB Heard my 10 meter beacon from the DR.  28,233.5 MHz  On now. 

-- Rick N3FJZ  Great memory Direct Conversion messages. 

-- John KN6FVK had fun with DC RX. Tattoos on Board. We need a high sign! Like the Little Rascals. 

-- Adrian M7EFO DC RX builder in GQRP.  FB.

-- Steve KW4H Kits not the same as homebrew, but old Boatanchor kits have value. 

-- Mike WU2D -- Old buddy Charles Kitchen SK. 

-- Craig -- Some really nice feedback on Hack-A-Day re DC RX and Dean's videos. 

-- Peter VK3TPM proposes a certificate for SolderSmoke DC RX Honor Roll. 

-- Michael WN2A used a 3 inch reflector from Northern New Jersey. Edmunds Scientific "Space Conqueror"  

-- Phil W1PJE and Mike WN2A lament that our eyes don't pick up radio frequencies.  This would be a great troubleshooting tool! I can SEE the IMD!  Perhaps some tin foil hats? 

-- John WPE9IRS SW listener! Heard my beacon.  Many SWLs switching to tuning in ham stations. 

-- Peter VK3YE found a homebrew 160 meter double-sideband transciever at a hamfest.  He also found "Solid State Basics for the Radio Amateur -- A QST Anthology"  NOT SSDRA.  But good!

-- Peter VK2EMU  From the Southern Cross (I took a picture of it in the DR!)  Building the DC RX!

 

Ramakrishnan VU2JXN

Homebrew vs. Kits -- The influence of Russian Homebrewers

 

Click on the image for a better read. 

Like Kirk, I too was influenced by the Russian and Eastern European homebrewers.  As a kid, every issue of QST seemed to contain (especially in the "How's DX?" column) pictures of intrepid Russian homebrewers seated next to their HOMEBREW stations.  I wanted to be like them. 

When I first launched the Direct Conversion Receiver Challenge, someone decided that it would be better to make the receiver into a kit. He criticized me for deciding to keep this project homebrew. There seemed to be a lack of understanding of the difference. This morning I got an e-mail from Kirk NT0Z. He attached his column from the February 2013 issue of Monitoring Times. I think he captures very well the difference between kits and homebrew. An excerpt from the column appears above. I need to get a portrait of UW3DI to hang above my workbench. Thanks Kirk.

Here is more info on the UW3DI transceiver:

https://www.cqdx.ru/ham/ham-radio-news/the-legendary-diy-russian-uw3di-transceiver/

Use Google Translate on this site: https://uarl.com.ua/bylsluchay/autor/ux0un_vivat_uw3di.html

The Hall of Fame -- Completed SolderSmoke Direct Conversion Receivers (So far --- more to come!)

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 April 29, 2025  0942Z:

So far 59 completed receivers, with 4 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

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

Honorable Mentions: 

*AA7U            Steve No PTO

*VK7IAN        Ian -- No Manhattan boards 

*KC1FSZ        Bruce's build on a PC board

*CT7AXD       Graham -- different AF amp

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

Candidates for the Hall of Fame: 

SA5RJS              Rasmus

KA9TII               James

W2AEW             Alan

AA7FO              Chuck 

K7WXW            Bill 

W1PJE               Phil  MIT

VA3ZOT           Tony  Surface Mount -- Honorable Mention? 

KM5Z              Mike Yancey

AB2XT             John (Done, just need the video)

KO7M              Jeff (Piper Cub)

KD4PBJ           Chris

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

FCC to Ban Direct Conversion Receivers

From the FCC News Line:  

The Federal Communications Commission announced today that it will soon ban a wide range of communications equipment due to interference that this equipment is causing to Starlink communications satellites in Low Earth Orbit (LEO).  The banned equipment includes a range of legacy analog-type circuitry that, according to the Commission, has "lost relevance" and constitutes "an archaic electromagnetic nuisance."  Under the proposed Commission action, banned equipment will include all regenerative, super-regenerative, and direct conversion receivers.  

The interference potential of regenerative receivers has been known since the 1920s.  Direct Conversion receivers were thought to be less prone to Problematic Spurious Emission (PSE),  but in recent months  LEO satellites have experienced serious interference from terrestrial sources.  

An FCC official was nearly apoplectic when speaking about the devices that are causing this interference:  "They have no shielding.  They are built on wooden boards, and are made with superglue!  Heck, the main tuning device is -- get this -- a screw! A screw!  To think that something like that could threaten an entire LEO satellite system.  This is really unacceptable."  The official said that two persons in Northern Virginia had encouraged the construction of these "terrorist devices."  The FCC is working with the FBI and the Department of Homeland Security to bring these people to justice. 

The vast majority of the interference is believed to come from home-made ("homebrew")  direct conversion receivers.  These devices employ simple oscillators in the 7 MHz range.  The 85th harmonic of these oscillators falls in the middle of the UHF frequencies used by the satellite system.  The interference appears when the satellites are over areas known to be used by ham radio direct conversion enthusiasts.  There have been communications issues near Melbourne  Australia, the North Island of New Zealand,  Bali Indonesia, all across the U.S. (especially in the area of Nashua, NH), Canada, the UK,  Holland,  and Sweden. Recently there have been reports of interference from Argentina. 

A satellite company CEO of has been briefed on the matter, and promised to use his influence in the U.S. government to "squash this problem like a bug."  The spokesperson for a major ham radio organization in the United States reassured members: "Don't worry, commercial SDR transceivers will not be affected by this ban." 

Homebrew Challenges Much Like Ours: The Direct Conversion Receiver of Wes Hayward W7ZOI and Dick Bingham W7WKR -- QST November 1968

 

https://www.worldradiohistory.com/Archive-DX/QST/60s/QST-1968-11.pdf

I was thinking about some of the challenges faced by the builders of the SolderSmoke Direct Conversion Challenge Receiver, and about how similar these challenges are to those described by Wes Hayward W7ZOI and Dick Bingham W7WKR in the November 1968 QST article that launched the direct conversion revolution among radio amateurs. You can read the full article beginning on page 15 in the link above.

Some observations and comparisons:    

--The November 1968 QST article said, "This receiver was designed for simplicity and ease of duplication, rather than ultimate performance."  Ours too! 

-- Wes's receiver has a single tuned circuit in the BP filter.  Ours has two LC circuits. 

-- Wes's mixer is also a diode ring.  He starts out using hot carrier (Shotkey) diodes, but later concludes that ordinary diodes would work just fine.  We reached a similar conclusion.  But I wonder if the ordinary diodes would work well with a low output level from the single FET VFO (see below). 

-- His oscillator uses a single MPF-102 in a Hartley configuration with no voltage regulation, and no buffer.  We have two active devices and a Zener diode.  This article makes me think we could have made our PTO even simpler.  

-- Wes's receiver has a low-pass filter between the mixer and the AF amp.  The cutoff is at around 2 kHz.  This seems quite low in frequency and may reflect a preference for CW.  It features 88 mH coils that are now quite hard to find. The goal of this filter seems to be to prevent signals from beyond the audible frequency range from overloading the AF amp.  We ended up using the diplexer from the W7EL optimized QRP rig.  I think this diplexer takes care of the problem.  

-- The W7ZOI/W7WKR receiver has no AF nor RF gain control.  When encountering a strong SSB signals, the article recommends detuning the BP filter.  I think our AF gain control, and the mod calling for an RF gain control will give the operator, well, more control and will prevent strong SSB signals from overloading the AF amplifiers.  The RF gain pot might also help prevent SW broadcast AM breathrough. 

-- One big difference between our receiver and the November 1968 QST receiver:  isolation of the VFO.  The QST article puts the VFO in an aluminum box above the chassis.  We have the PTO without any shielding right alongside the other circuits.  Builders might want to experiment with the kind of isolation recommended by the QST article.  Would this kind of isolation and shielding improve performance? 

-- Wes also obviously contended with oscillation by the AF amplifier, as did many of our builders.  The QST article contains a number of recommendations: First test the amplifier to see if you can hear noise.  If it oscillates, try increasing the value of the decoupling resistors. (Many of our builders added electolytic caps to the DC power line in the AF amp.)  The article recommends trying a .01uF cap across the output.  It also recommends keeping the output of the amplifier away from the low pass filter at the input.  Wes's design has no transformer as it makes use of high Z headphones. 

-- The QST article says that the product detector performed adequetly with an LO injection level of .6 volts peak-to-peak.  This seems quite low to me,  but perhaps this would work with hot carrier diodes in the diode ring?    This might be one good reason to use diodes that have a lower turn-on voltage -- you could get away with using a super-simple VFO even if it provides lwer voltages to the mixer.  It might be fun to experiment in this area.  

As readers can see, the challenges faced by the builders of the SolderSmoke DC receiver were very similar to those face by the builders of  the November 1968 machine.  I think all of us should find this very encouraging.  

Thanks again Wes and Dick. 

Andy KB7ZUT is a Good Sport -- He Built the Direct Conversion Receiver HIS WAY, then OUR WAY. Great StarTrek Cartoons

 

Early on, Andy sent in a report on a Direct Conversion receiver that he had built.  It looked kind of like ours, but it was clearly NOT ours.  It even had a 20 db RF amplifier ahead of the mixer.  We politely (I hope) pointed out the differences.  Andy quickly came back with the receiver picutred above.  Yes, that is ours!  Thanks Andy! 

Andy writes: 

I'm calling it done (for now)! 1) Biggest challenge for me was "coloring inside the lines". In other words, building the actual DCR challenge to the schematic vs. getting too creative with other circuits in my head.  2)My biggest breakthrough was developing a much better understanding of the diode ring mixer.  And how brass displacing air in the PTO works. 3) What's next? I want to try some transformer-less audio amps to see if I can find a design for the folks that are having trouble finding a cheap source for the 1000/8 transformer.  A super big thanks to both Bill @N2CQR and Dean @Soldersmoke for all the hard work bringing the DCR challenge and the Discord community to life. Bravo! And I would also like to thank Pete (N6QW) our guiding light and spiritual leader too. If it wasn't for the SolderSmoke Podcast and the Blog, I would still be living life as an appliance operator.  73 KB7ZUT ..

Andy posted these to the Discord server: 

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 

Wayde VA3NCA Receives SSB, CW, FT8, and CHU Canada on his SolderSmoke Direct Conversion Receiver

Above you can watch and listen to Wayde's receiver as he tunes across 40 meters. It sounds good, even though Wayde is thinking about some improvements. 

 It was highly appropriate that Wayde's first reception report should be of CHU Canada, the Canadian time signal on 7.850 MHz, a bit above the 40 meter band, but clearly in tuning range for an unmodified SolderSmoke direct conversion receiver.  CHU is probably unique in the world in that it is transmitting the carrier and JUST ONE SIDEBAND.  It transmits only the upper sideband.  This makes it clearly detectable by our receiver.  As Dean pointed out to Wayde, all he had to do was "zero beat" the carrier with the PTO signal (tune to the point where they are on the same frequency and the audio tone disappears).   Because there is only one sideband, the direct conversion receiver can demodulate it very well.  If there had been two sidebands, this would have been a standard AM signal, and our little receiver -- which does very well with SSB and CW -- would have been unable to demodulate the signal without distortion. (For an explanation of why this is, see: https://soldersmoke.blogspot.com/2022/12/but-why-why-cant-i-listen-to-dsb-or-am.html   Warning -- this is kind of in the "advanced course" category.)

Here is an overhead shot of Wayde's receiver: 

This is a really nice build.  The use of what appears to be a kitchen cutting board harkens back to the early days of radio when young hams took the cutting boards from their mothers' kitchens and used them as bases for rigs.  This is origin of the term "bread board."  Frank Jones continued in this tradition by building most of his rigs on wooden boards.  Wade's DC receiver continues in that tradition. 

Wade was able to decode some FT8 picked up by this receiver and recorded on his phone: 

Congratulations Wade!   

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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 

Jim KF8BOG Completes the SolderSmoke Direct Conversion Receiver after a Long, Hard Journey of Discovery

Herodotus once said that "learning is not child's play -- we cannot learn without pain." I think Jim KF8BOG proved that in this build.  I'm sure he burned his fingers at least a few times.  I remember fondly almost seeing the light buld turn on when Jim came to understand how the diode ring mixer really works.  He struggled to tame a rebellious AF amplifier (we've all been there).  Throughout Jim demonstrated the persistance and determination that are needed to turn a bunch of parts into a well-functioning receiver.  He did it. He built it.  Congratulations OM!  

 Jim wrote: 

I am not just an appliance operator now but only half way through. Time to make a transmitter!   

A little about me I became interested in Ham radio about 45 years ago in Boy Scouts I tried really hard with my Radio shack straight key and morse code chart to learn code by myself and just could never get it.  Fast forward to last year and I had a friend who did CERT and he told be about it and said he used 2 meter for communications I was impressed and said “how did you learn morse code?” he replied “ I didn’t you don’t need it anymore”  I promptly signed  up for Ham in a day in June and got my technician license and my then my general in August. I have been studying radio ever since.  This project was perfect for me. I like to make things I have been a mechanic for 40 years plus ASE master.  Fixed all sorts of crazy electrical issues but DC and RF are way different lol. 

Again Thanks Bill and Dean you don’t know what you have started.  73s KF8BOG

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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 

VK4PG's Wonderful Australian Direct Conversion Receiver from Sunny Queensland

It was really great to hear those Australian voices coming from Phil's receiver.  Check out the video above. 

Phil writes:  

Completion!  So pleased, it works really well.  And there were lots of lessons for me along the the way.  Thank you Dean, Bill and Pete, it's been a great way to get me into homebrewing.  73s from sunny Queensland.  Phil VK4PG

I also like Phil's front panel.  Note how he put to use the circular piece that remained after cutting the speaker hole; that became the tuning knob.  FB Phil.  Thanks. 

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 

Derek N9TD's SolderSmoke Direct Conversion Receiver -- With a Double Sideband Transmitter

 

Derek N9TD was another of the early builders of the Direct Conversion receiver; he has done really magnificent work.  He is an Electrical Engineer, and you can see in his work (and in the email below) the tension that exists between the desire for simplicity and the urge to improve.  In the above photo, for example, we see that Derek had already gone ahead with the installation of an RF gain control. We also see his use of a steel screw and an outboard coil in series with the PTO coil.  All of these mods are fine -- I have used all of them. We just advise newcomers to build the basic receiver first, then put in mods from there. 

Derek has gone the extra mile (many miles in fact) by building a Double Sideband transmitter to go along with his receiver.  We know many will want to do this.  Our advise remains:  Build the basic receiver first, get it working, then do the mods, perhaps culminating in the build (as Derek did) of a Double Sideband transmitter and the creation of a DC-DSB transceiver. 

Here is a video of just the receiver in action.  

Note that the DSB transmitter circuitry is on the board:     

And here is Derek demonstrating a phone contact with the resulting DC-DSB transceiver:  

Derek wrote: 

Bill, 

Let me introduce myself, I am a recent electrical engineering graduate from Purdue and a long-time listener of the podcast. I want to thank you and Pete for being one of the reasons I chose to pursue my degree in the first place. I'll admit that in the more difficult stretches of getting my degree, I often pulled out the podcast to be reminded of the fun that can be had with radio and electronics.

Until recently I had to hang my head low along with the majority of the other 'appliance operators' out there having never built anything with my two hands that can be used to pull signals out of the ether.

 I am no stranger to building projects, PCBs, and melting solder but I usually chose to either stick to the dreaded digital domain or focus on antennas, filters, and other ancillary equipment. The logic being that I like to have a "known good" radio for the shack and that I would focus on other equipment to supplement the radio. I still follow this logic when I want to contest and we all know that antennas are well worth the effort, I've just finally had enough of being an appliance operator and have your podcast to thank for the extra push. 

I had been following the original effort of the TJ DCRX with interest from the start and earmarked this project as one I would like to build based on its inherent simplicity and good performance. However, the demands of school and a recent (at the time) abortive attempt to build an AM superhet with an SA602 the year prior made me  (I got as far as feeling the joy of oscillation but regretfully petered out after that) put this one the backburner for about two years until December 2024.

By coincidence, I independently decided to start this project just before your show with the HRWB folks and the gauntlet being thrown down, which has spurred many to build this receiver. It has been great to see the extra coverage on the receiver, and the commentary has been very insightful for someone trying to build this for the first time and with as many of the "improvements" as possible. 

For better or for worse, I'm the type of guy who wants to understand the "why" behind all the design choices and, from there, try to incorporate as many lessons and improvements as possible to make the "best" version possible. I'm not saying I make the best version of anything, but it's just a quirk of the way I think and justify doing a project. It always has to be "this and some additional improvement;" otherwise, I would decide against doing it. 

Rambling aside, I ended up building the DCRX, adding the RF attenuator from N3FJZ's website, and incorporating the lessons you learned after experimenting with improving the tuning on the PTO. I added an external series inductor wound on a dowel rod and used a zinc-coated steel screw as opposed to brass. I found that this gave solid tuning performance across 40m and was easy enough to tune in CW or SSB signals (after 3D printing a large knob for the PTO bolt). Alan W2AEW's video on mixers was a great tutorial to use to verify that my mixer was mixing. With the radio assembled I was treated to the joy of hearing my receiver breathe in the sounds of 40m for the first time last weekend and even managed to copy some Croatian DX during last week's contest. As Farhan said to do, I have spent the last few days enjoying the receiver and figuring out its quirks before moving on to the next step. 

The only "issue" I have noticed is that I still get some AM breakthrough despite tuning in the bandpass filter. The problem is very noticeable if I accidentally put my finger on the wires going to the AF gain pot. If I do that the AM station is the only thing I can hear. This makes me think the problem is after the bandpass filter and more investigation is needed. Maybe using coax on the control lines to shield it will help? Regardless I am impressed with how well the receiver sounds, the stability of the oscillator, and the effectiveness of the simple audio amp....  

Again thank you and Pete for your work on the podcast and for helping inspire countless homebrew radio operators! 

73s,

 Derek N9TD

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

Thanks Derek.  And thanks for helping other hams get the 3D printed PTO coil forms that they needed. 

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 

Scott KQ4AOP Built the SolderSmoke Direct Conversion Receiver, and Listened to his FIRST EVER Ham Signals with it

Scott KQ4AOP's build of this receiver is especially noteworthy, becasue he used the receiver to hear the very first ham radio signals he ever received.  I don't think any of us can make a similar claim.  

Scott wrote:  "Those first sounds were my first time ever hearing any Amateur Radio first hand!" You can see Scott's deep commitment to homebrew: "I want to build my own gear for 40m. I want to learn morse code. I want my first contact to be on my own gear."  Wow Scott, the building of the receiver is the hard part, and you have already done that.  I think you are well on your way.  In the video above you can watch Scott tune the entire 40 meter band and a bit beyond. You hear CW at the low end.  Then FT-8.  Then SSB.  Up just above the top of the band I think you can hear our old nemesis Radio Marti.  And this powerful broadcaster is NOT breaking through on the rest of the band.  FB Scott.  Congratulations.  

Check out this blog post and the comments: 

https://soldersmoke.blogspot.com/2024/02/scott-kq4aop-successfully-builds.html

Scott has also exhibited true ham spirit by 3D printing PTO coil forms for those who need them.  This has helped many other hams build the receiver: https://soldersmoke.blogspot.com/2025/01/scott-kq4aops-pto-coil-forms-for-high.html  

Thanks Scott 

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