Comments on the SolderSmoke Direct Conversion Receiver from Andri in Bandung, West Java, Indonesia

Congratualtions to Andri, of Bandung, West Java, Indonesia.   Andri successfully built the SolderSmoke Direct Conversion receiver.  (See the the Short below for a video of his receiver in operation.)  Like many, he had some trouble getting the AF transformer -- so he took one out of an old Japanese transistor radio.  He needed the FET for the PTO, so he made due with a surface mount part.  All this by someone who does not have a ham license.  I think he deserves a license, solely based on his successful build of this receiver.  He has done something that most hams will never do:  He has homebrewed a receiver.    Thanks Andri!

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

Comments from Andri: 

I am just a newbie and not a ham radio operator, so I don't have a callsign. I do enjoy building electronic things though even though I have no background in electrical engineering.

It was a nice rewarding experience building this receiver. The challenging part was sourcing some parts which are hard to come by here in Indonesia such as the toroid cores, JFET and audio transformer. So I substituted FT50-6 with FT50-2, T50-43 with ferrite core for SMPS, and I use an SMD JFET instead.

Thank you very much for the detailed instructions on how to build this radio. Without them I would be lost. Ham radio has always been intriguing to me, but I never got into it because it is a prohibitive hobby.

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

Bandung Wiki: https://en.wikipedia.org/wiki/Bandung

137 Direct Conversion Receivers -- Recently Built in Bandung, Indonesia. But none in Japan, None in China, None in Africa, and only 1 in all of Latin America!

RX built in Bandung Indonesia -- Andri used an AF transtormer from an old Japanese receiver. 

Why have NO receivers been built in Japan?   And none in China.  Only one in all of Latin America. Not one in all of Africa.     

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. 

As of July 21,  2026 0930Z:

So far, total receivers built: 137 (129 plus 8 honorable mentions).  Total Count:  137.  Receivers built in 19 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  (Canada)  

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 (Netherlands) 

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 (Australia) 

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!)  (England)  

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  (England) 

W2DAB           Dave in NYC

W4JYK            Wes of VWS

KA4CDN          Mike of VWS

M7EFO             Adrian 

VK5RC             Rob  (Australia) 

KD8KHP          Dave

VK1CHW         Chris (Australia) 

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 (India)

W1DSP             Rick

WD4CFN         Steve

KM5Z             Mike

KF5DAN         Dan

Fritz                 Fritz

N9OK              Joe

WA5DSS         Bill 

K0GDB           Grant

G0JNR            Shane Glow-in-Dark Coil Form

KK7BCO        Tobias

K2BVR            Bob

Robert              Sutton

K5YFO           Dave (Texas) 

KD4PBJ          Chris

KN4GAH        Chris -- EE perspective

F1GMA           Philippe  -- (France)

W2TEF            Todd

EI9ITB            Karl  -- (Ireland)

VU2TUM         Puneit Singh (India) 

AA7EE             Dave Richards

KI5VIR            Jay

CT7AXD       Graham -- Promoted from Honorable Mention! (Portugal)

G3MOT           Josh (England)

KW4H             Steve

NJ7V                Charlie (RedSummit)

N2ETZ            Denny

AB9LM           James

W9XT              Gary

G0PJT             Alex

KF8FZZ         Tyler

N7HPR           Steve (Instructor) (N7HPR Group)

Clark               (N7HPR Group)

KQ4ZHO        Kurt (N7HPR Group)

KQ4OBR        Brian (N7HPR Group)

KR4CUF         Justin (N7HPR Group)

Amanda          (N7HPR Group)

David               (N7HPR Group)

KM4AED       Jamey (N7HPR Group)

KN4MVH      Larry (N7HPR Group)

N5GVW          Dick (N7HPR Group)

W7KAL          Kal

KC9LFP         Joe

SP9DEL         Marian (Poland) 

LB8VA           Ivar (Norway)  

AA7FO          Chuck Adams! 

WE6Z            Doug

N7MN            Jason

VA2GJ           Gerald in Quebec

N6HA             Bill 

Andri             Bandung, West Java, (Indonesia)

Scott               K6AUS  

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

Honorable Mentions: 

*AA7U            Steve No PTO

*VK7IAN        Ian -- No Manhattan boards -- (Tasmania)

*KC1FSZ        Bruce's build on a PC board

* DL1AJG      Andreas -- (Germany)

* Matthew      Student of DL1AJG

* Arash           Student of DL1AJG 

*KA4KXX     Walter -- FB 20 Meter version

*M9KCA-ST2NH  Nader - LM386 in place of AF amp

Canadian Ham to Include SolderSmoke Direct Conversion Receiver in Teaching Materials for Canadian Ham License

Good morning Bill N2CQR.

I currently teach Canadian amateur radio certification courses.

The Advanced certification (akin to the FCC Extra Class license) has topics nicely showcased with the NorCal 40a transceiver.

Happily, the SolderSmoke DCR project will be included in my next editions of teaching materials (books, zoom presentations, monthly newsletters) once the Canadian question bank revisions are published later this year.

I really learned a great deal from the YouTube videos for each module in the DCR. Especially appreciated were the recommendations for trimpots and how to use them in the RF filter and the back-to-front build-test procedure for the cascaded audio amplifier. And these are just 2 of the many precious circuit building strategies learned from the documentation supporting this project.

Kudos to you and Dean and all the people involved at SolderSmoke.

All the best, 73 de VA2GJ, Gérald Julien Lemay.

Nader M9KCA-ST2NH's Beautiful Build of the SolderSmoke Direct Conversion Receiver: NO SMOKE!

 Nader wrote: 

Hello everyone! After more than 30 years, I've rebuilt the DCR again. I wanted to share the fun of the 40m SolderSmoke DCR Challenge with all of you. It was a fantastic project — fully documented, with many people sharing their experiences online. I'm truly delighted to show you my prototype. The best part? It ran from the very first power-up — no smoke, no tuning needed! Yes, all on one board. The audio amp isn't quite ready to challenge the role yet, but it's still a lot of fun.

Nader's Sudanese callsign rang a bell with me.  I had talked about him in SolderSmoke podcast #58 on May 13, 2007.  Here it is:  https://www.soldersmoke.com/soldersmoke58.mp3    And I included a long quote from him in the SolderSmoke -- Global Adventures book.  So Nader is an old friend indeed.  

He clearly built the receiver, with excellent results.  He used the innards of a glue stick to build the support for the PTO inductor.  But he has not yet built the three-transistor AF amplifier.  So, in the interim, I am placing him in the "Honorable Mention" category.  When he completes the AF amplifier, he will be promoted to full membership in the Hall of Fame. 

G-QRP 2025 G2NJ Trophy

Thanks to G-QRP for selecting us for this prestigious award.  This was for our efforts with the SolderSmoke Direct Conversion Receiver.  

The ARRL's 2025 Technical Service Award

 

Audio Amplifier Stage Template and Handout: SolderSmoke Direct Conversion Receiver by N7HPR

 

Above is Steve N7HPR's template for the audio amplifier board, the board that gave a lot of people a lot of trouble.  But it SHOULD have caused a lot of trouble!  It is the only gain stage in the receiver -- it provides at least 80 db of gain.  It deliberately uses no feedback -- we did it this way to keep the circuit simple.  So if you let too much of the output find its way to the input, this amplifier will turn into an oscillator.  Then you will have to tame it. And almost all builders did. This was a valuable lesson:  All amplifiers aspire to be oscillators.  They have to be denied the Barkhausen criteria. 

Above we see the placement of Rex's Me pads, and the transformer. (Note that Steve DOES ground one of the output pads.)  I think that Steve's layout was really good -- it sounds like they did not have a lot of the feedback and motorboating problems that were reported by others.  This is a good reminder of the importance of careful layout. 

Here is Steve's handout: 

Steve's messages have caused me to reflect a bit on this project.  I will try to write about this in the days ahead.  

Thanks Steve. And thanks to all the builders. 

SolderSmoke Direct Conversion Receiver: TOROIDS! Steve N7HPR's Handouts on the BP Filter and the Mixer/Diplexer

 

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

Winding the trifilar toroids was the hardest part of building the mixer board, and with the high school students, I admit to chickening out.   Instead I prepared about 17 of them using a batch from Hyderabad (wound by the seamstresses!) that Farhan left me.  Here is  how we did it: https://soldersmoke.blogspot.com/2023/02/progress-report-high-school-students_25.html Steve's use of wires of different colors is a good idea.  It helps to keep track of the different wires.  

We often hear that winding toroids is a show-stopper for many would-be homebrewers.  This should not be the case.   Winding the coils is not difficult.  

The Diplexer came from Roy Lewellan W7EL's optimized QRP Transceiver.  Dean and I were struggling with the suppression of signal from Radio Marti on 7335 kHz.  When we added Roy's diplexer, it seemed to help knock down Radio Marti.  

We too used the NanoVNA to tune the BP filter.  I remember this as one of the more pleasing moments for the students. 

SolderSmoke Direct Conversion Receiver-- N7HPR Handout #1 -- The VFO

 

I like the way Steve N7HPR did this:  First, that he had a working receiver on display to serve as a prototype.  Second, that he asked the students to come up with their own Manhattan board designs and third, he provided templates that would allow them to properly place their Me Pads. 

We did some of these things with the high school students.  We definitely had a prototype on display, and they looked at it a lot.  We did ask them to deisgn their own Manhattan boards -- as I recall, the response to this was uneven at best.   The templates are a good idea that we did not try with our group build.  

One big advantage of building the VFO first -- the students get something of the Michigan Mighty Mite sensation.  They have successfully built a source of RF, a transmitter!  We had one of the students move around the room with his oscillator (battery powered) turning it on and off as he listened to the tones from a DX-390 receiver.  This is very similar to the demonstration that Marconi did with the very first radios.  

More tomorrow.   

Thanks again Steve.

Steve N7HPR Describes the Group Build of 10 SolderSmoke Direct Conversion Receivers

Group Build of the SolderSmoke Direct Conversion Receiver Challenge

By Steven Bible, N7HPR

Andrew Johnson Amateur Radio Club and Greene County Makers, Greene County Tennessee

The main goal for the group build is hands-on learning. Each of the students are working on their amateur license. Three are working on their Technician, one General, and the remainder on their Extra. The extra exam has a great deal of detailed technical knowledge and the SolderSmoke Direct Conversion Receiver Challenge is a great vehicle for teaching many of these technical details.

Several in the group have experience soldering thru-hole components on a printed circuit board. However, Manhattan style construction was new to them. It would add a valuable skill to their toolbox. The question, from an instructor’s point of view, was how to ease them into this skill before taking on a much larger project? The answer was to first build a smaller project to introduce the students to this unique construction style. I chose Allen Wolke’s W2AEW YouTube video on building a buffered Colpitts crystal oscillator. The added benefit was teaching the oscillator questions on the amateur exams.

#123: Build a crystal oscillator from schematic thru prototype construction and

testing – DIY [https://www.youtube.com/watch?v=blalAktxFoI]

In the video, Allen shows how to identify the nodes on a schematic and use them as the

pads on the PCB. From this I came up with a teaching method where the students study

the schematic and sketch on a handout how they plan to assemble the board. I

designed and 3D printed a template for the student to trace onto the PCB with a pencil.

They would superglue MeSqares onto the squares of the template, and the circles were

suggestions of where to ground components to the PCB. This gave them the mental

exercise to reason how to take a schematic and turn it into a prototype. Building the

oscillator was an excellent introduction and helped lead the students into the larger

DCR Challenge.

PCB Template. Students sketch the template onto the PCB.

Over the course of eight weeks of 2-hour classes, the students built the four blocks of

the Direct Conversion Receiver. I designed and laser cut a baseboard from 1/8-inch (3

mm) Baltic Burch plywood where the students could mount the four blocks of the

receiver. This provided the students some structure in assembling the receiver.

We started with the VFO block first. The most challenging thing was winding the PTO

form. But everyone managed. Other challenges were poor solder joints and missing

connections, which were easy to remedy. They became excellent teaching points.

I also noticed that students would look at the (what I called) the prototype Direct

Conversion Receiver that I built to show everyone what it would look like in the end. As

it turned out, this was a valuable part of the group build. Students would take photos of

the prototype so that they could gain a better understanding of the construction of the

receiver.

As students completed their VFO, I would test it using an oscilloscope demonstrating to

them what and how an oscilloscope works and the signals coming from their VFO.

The second block was the Band Pass Filter. This block had easier transformers to wind

compared to the mixer. This allowed a gentler introduction to toroid winding. To aid in

the identification of the windings, I purchased red and green enameled wire that had a

poly-coat that was easy to remove using a blob of solder on the soldering iron. Overall,

this was a simple block for the students to assemble. As students completed their Band

Pass Filter, I connected it to a nanoVNA and allowed them to tune the filter. Another

great teaching moment introducing them to filters and vector network analyzers (VNA),

all if which are on the General and Extra exams.

The third block to be assembled was the Mixer. This had a little more challenging

transformer with the trifler windings. I purchased enameled wire in three colors: copper,

red, and green. The copper-colored wire was coated with enamel which required

scraping to remove. The red and green was the poly-coating the students were familiar

with from building the Band Pass Filter.

The three colors allowed the students to identify the primary (indicated with a dot on the

schematic) and secondary sides. The schematic showed the location of the colors and

the MeSquares they were to be attached to. This alleviated much of the confusion that

can occur with connecting trifler windings (see DCR Mixer Handout.docx).

The forth block was to assemble the Audio Amplifier. By this time the students have

developed their knowledge and skills to assemble the one block that had the most

components. Assembly went smoothly; however, we would have the occasional

misplaced component, bad solder joint, etc. This was the case throughout the build, but

they were welcomed as excellent teaching moments.

When the entire Direct Conversion Receiver was assembled, we would test them first

using a tinySA in signal generator mode and inject a 7.1 MHz carrier. We would tune the

PTO to tune down to 7.0 MHz and up to 7.3 MHz. We had to add an inductance in

series with the PTO to accomplish this range. This took some trial and error. There was

some troubleshooting to be done to find an error or two. Finally, we connected the

receivers to a loop antenna and listened to on-the-air signals. It was not the best

antenna setup, but it gave the students confidence that their receivers were working.

The amateurs in the group took theirs home and hooked them up to their station

antennas to listen further. Each reported good reception.

The Soldersmoke Direct Conversion Receiver Challenge was an excellent group

project. The students learned a great deal from the hands-on experience. W2AEW’s

buffered Colpitts crystal oscillator video was perfect for introducing Manhattan style

construction. Creating a kit of parts, 3D printed templates, handouts, and laser cut base

gave structure to the group build and minimized construction errors. Having a fully built

receiver (that I called the prototype) for students to refer to proved extremely valuable.

Building as a group provided an encouraging environment where the students would

assist each other and share teaching moments (what to do, what not to do). Finally,

there were many teaching moments that helped solidify knowledge and skills and there

were many direct references to the questions on the Technician, General, and Extra

exams. The goal of the group build was met!

Many thanks to the SolderSmoke team for an excellent project!

73, Steve N7HPR

Thanks Steve!  More to follow -- Steve's handouts on the construction of each stage are really great. 

 Stay tuned!

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

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/ 

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

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? 

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

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. 

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

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.  

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

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.