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!

Why is it that AI-provided electronic circuits often don't work in the real world?

Like many, I have turned to AI for circuit ideas.  And like many, I have been surprised by how many of these ideas just don't work.  I have found relatively simple circuits that don't work when built in the real world, and don't work when built in LTSpice. I have already described how AI failed when I asked it a simple question about how many 330 ohm resistors to put in parallel to get 50 ohms.  Mike WU2D had found that a lot of AI provided circuits just don't work.  (Go to the 10 minute point in his video. )

I was wondering why this is so.  So... I asked AI!  For those who are sure that their AI is smarter than my AI, let me specify:  I just wrote the question into the Google search box and looked at the "AI Overview" in the response.  

Here is what AI said: 

AI-recommended circuits often fail in the real world due to gaps between simulation and reality, such as a lack of real-world data (noise, rare conditions), AI's inability to grasp complex physical nuances like heat dissipation or component aging, and poor integration with physical prototyping, leading to brittle designs that don't account for manufacturing tolerances or environmental stresses, despite being mathematically sound. 

Key Reasons for Failure:

Data Limitations (Garbage-In, Garbage-Out): AI relies heavily on training data; if it's incomplete (missing extreme temperatures, noises, aging effects) or biased, the AI generates designs that work in simulation but not in messy real-world conditions.

• Brittleness & Lack of Context: AI struggles with "edge cases" or novel situations not in its training, leading to fragile designs, much like an AI failing to recognize a rotated bus. It lacks human intuition for subtle physical interactions.
• Physical Nuances Ignored: Simulations often miss crucial real-world physics like heat hotspots from component imperfections, electromagnetic interference, or subtle signal integrity issues, which become critical in physical prototypes.
• Manufacturing & Prototyping Gaps: AI designs might be theoretically optimal but impractical to build (e.g., impossible tolerances, complex layouts). The gap between virtual design and physical assembly (poor connections, wrong components) causes failures.
• Validation Challenges: AI-generated circuits need extensive, real-world testing (SPICE simulations, breadboarding, PCB builds) to catch issues, but AI can't perform physical troubleshooting like soldering a damping resistor or witnessing ground bounce in a lab.
• Probabilistic vs. Deterministic: AI works on probabilities, whereas electronics often need deterministic precision. A small error tolerable in some AI tasks can be catastrophic in sensitive circuits. 

How Engineers Address This:

• Iterative Feedback Loops: Combining AI's speed with human expertise and physical testing to refine designs.
• Hybrid Approaches: Using AI for creative exploration but relying on established physics models (like SPICE) and human judgment for final validation.
• Focus on Integration: Ensuring AI tools work seamlessly with existing engineering workflows and physical constraints. 

Walter KA4KXX's Innovative 20-meter SolderSmoke Direct-Conversion Honorable-Mention Receiver

 

It is a thing of beauty.  We were really pleased to see our old friend Walter KA4KXX take on the SolderSmoke challenge, and we weren't a bit surprised to see him do so using some real twists in the design.  You see, Walter is a very experienced homebrewer.   He has built many, many rigs over the years.  Just check out his QRZ page and you will see what I mean: 

 https://www.qrz.com/db/KA4KXX

Walter supported our original high school effort by offering the students a $500 prize for any student who used our receiver (and a similar transmitter) to check in to the 40 meter Sunrise Net.  Sadly, there were no takers.  But we really appreciated the attempt. 

We have listed Walter's receiver in the Honorable Mention category, only because his build is so innovative:  20 meters instead of 40.  An IC in the audio amplifier.  There were differences, but even a quick look at the above picture above shows that Walter's receiver is very much a SolderSmoke Direct Conversion Receiver.  

Here are some additional photos from Walter. 

Congratulations Walter.  Welcome to the Hall of Fame!  

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

From Walter's QRZ page

Pete N6QW Asks Copilot about Homebrew vs. Store Bought

Copilot is remarkably perceptive.   This AI-generated message really explains very well the differences between homebrew and store bought gear. 

Check out Pete's blog:   https://n6qw.blogspot.com/2025/12/mostly-ai-generated.html 

Homebrew vs Store Bought

There’s a moment every homebrewer knows: you shove aside the archaeological layers of past projects on the bench, uncover a few resistors stuck to a solder blob, and declare, “Yep, this is going to be a radio.” To the untrained eye, it looks like the aftermath of a nuclear explosion. But to the enlightened? It’s the beginning of greatness — or at least something that won’t catch fire too quickly.

Buying a radio is easy. Too easy. You click a button, a box arrives, and suddenly you’re the proud owner of a rig that has more menus than a chain restaurant. You spend the first week scrolling through settings trying to figure out why the audio sounds like a kazoo trapped in a tin can. But building a radio? That’s where the real fun begins. It’s where you learn that “datasheet recommended values” are merely suggestions and that toroids exist solely to test your patience and your vocabulary.

Commercial radios are sleek, polished, and packed with features you’ll never use but will brag about anyway. They’re also sealed tighter than a politician’s tax returns. You can’t poke around inside without voiding the warranty, the warranty’s warranty, and possibly a few federal regulations. Meanwhile, a homebrew rig practically begs you to poke it with a screwdriver. It’s the difference between owning a sports car you’re not allowed to open the hood on and owning a jalopy you can rebuild with duct tape and optimism.

And let’s be honest: building a radio is an act of rebellion. In a world where everything is prepackaged, preprogrammed, and pre‑approved, choosing to melt solder and wind toroids is basically saying, “I reject your consumerist convenience and substitute my own chaos.” It’s a declaration that understanding matters. That learning matters. That the journey — the mis-wired stages, the smoke tests, and the moment you realize you soldered the IC in backwards — is part of the joy.

There’s also something deeply personal about a homebrew rig. When you build it, you know every quirk. You know why the VFO drifts when the cat walks across the table. You know why the audio chain hisses like an angry snake. You know the exact moment when the rig came alive for the first time, pulling a faint signal out of the ether and making you shout, “It works!” loud enough for the neighbors to wonder if you’ve finally snapped.

And that first QSO? Pure magic. When someone hundreds or thousands of miles away responds to your signal, you feel a surge of pride no store‑bought rig can match. You didn’t just operate a radio. You created one. You made electrons dance to your tune. You built a bridge across the airwaves using nothing but determination, caffeine, and parts that probably came from a cardboard box labeled “misc — maybe useful someday.”

Homebrewing also keeps the spirit of amateur radio alive. The hobby wasn’t built on buying the latest rig because the brochure said it had “enhanced DSP algorithms.” It was built on people who asked, “What if?” and then went to the bench to find out. When you build a radio, you’re participating in that legacy. You’re keeping the flame lit — even if the flame occasionally comes from a resistor, you accidentally overheated.

And let’s not forget the best part: when something breaks, you can actually fix it. No shipping it back to the manufacturer. No waiting six weeks for a repair estimate. No customer service rep telling you to “try turning it off and on again.” You grab a meter, poke around, and mutter, “Well, that shouldn’t be glowing,” and you fix it. That’s power.

Frank Jones W6AJF on Homebrew, Thermatrons, and VHF

We are in the Dominican Republic now. I thought SolderSmoke blog readers would like the introduction to Frank Jones W6AJF's VHF handbook. (Click on the pictures for a better view. ) The book was published in 1961.  Lots of good homebrew, VHF, and thermatron thinking in those pages. I will be using this book and the implied blessings of W6AJF in my upcoming 2 meter assault on the Mona Passage between the DR and Puerto Rico.  (Thanks too to W3RTV, the original owner of the book!) 

Click on the pictures for a better view. 

Click on the pictures for a better view. 

Homebrew Radio from Southern India

I came across this channel yesterday -- there is a lot of FB homebrew content here.  And it is partially in the Malayalam language of Kerala state in Southern India.  

About 38 million people speak Malayalam: https://en.wikipedia.org/wiki/Malayalam. 

Check out his channel:  

 https://www.youtube.com/@MrtechElectronics

Another GREAT Book -- L.B. Cebik, W4RNL's "Seven Steps to Designing your Own Ham Equipment" - 1979 - FREE!

Thanks to Walter KA4KXX for alerting us to this gem of a book.  L.B. Cebik is best known as an antenna guru.  I did not know that he also did a book on the homebrewing of rigs.  

Here is the URL: https://archive.org/details/sevenstepstodesi0000cebi/page/n2/mode/1up  Just click on the "borrow" box and you can look at the whole thing.  Thanks too to the Internet Archive for preserving this important piece of ham literature. 

I was a bit apprehensive when I saw "designing" in the title.  We have talked about how, all too often, modern hams seem to challenge the homebrew nature of our rigs by asking if we had "designed" it ourself.  "Well," I answer,  "I did not invent the Colpitts oscillator, nor the common emitter amplifier, nor the superheterodyne receiver... But I did build this rig myself."  I worried that OM Cebik might have been plunging us into this design debate way back in 1979.  

But no need for worry.  His definition of "design" is quite expansive:  

I have not read the whole thing yet.  I hope that others will go through it and highlight for the group the parts that they find to be the best.  Please put your thoughts in the comments section below. 

Thanks again Walter.

"Keep Calm and Solder On"

 

So not everything that comes from AI is bad. This AI generated picture is pretty good.  That actually looks a bit like my rig.  And as someone who has spent four years in the UK, I can really appreciate the "Keep Calm and Solder On" sign.  Indeed.  Words to live by my friends!  

A Wonderful Homebrew Direct Conversion Receiver (and other HB projects) from Italy

This morning I asked YouTube to show me recently posted videos of "ham radio homebrew."  The results were disappointingly meager... except for the content of this site, which were downright inspirational.

Don't let the Italian language bother you.  You can see what he has been doing just by watching the videos, the shorts,  and the posts. 

There is a lot of Manhattan-style construction here.  There is even a Tuna Tin 2 (made in a mushroom can!).  Above all, there is a lot of FB homebrewing in this site.  Va bene!  

Here is the YouTube site:  https://www.youtube.com/@SelectaCs   

Please view and subscribe.  He could use the visits and we definitely want to encourage construction like this.  

Also, who is he?  Who is "Selecta Cs"?  (Listening to his CQ in one of the videos, I think it is Samuele, IU2QBW.)

UPDATE:  It is Samuele IU2QBW.  He writes: Good evening, dear William!! It's a great pleasure to meet you, and I'm so happy to hear this email! Thank you so much! I'm flattered to have been featured on such an important blog as SolderSmoke! I'd be delighted to collaborate with you and all other DIYers!  Thank you so much again for the compliments and encouragement! It means a lot to me! A big 73 from IU2QBW Samuele

 

Hack-A-Day on the Tao of Bespoke Electronics

https://hackaday.com/2025/06/25/the-tao-of-bespoke-electronics/#comment-8142333

My comment:  Good post with good points about the under-appreciated differences between true homebrew and kit building. I have a lot of Heathkits around me, but I never considered them to be homebrew. There is a big difference. We have been promoting and supporting the HOMEBREW construction of 40 meter direct-conversion receivers. No one would confuse these receivers with commercial, or even kit-built gear. But they work very well, and the builder earns the satisfaction that comes with building something from scratch. There are no factory made PC boards to “populate.” All four of our boards are made using Manhattan construction techniques (super glue, isolation pads, copper-clad substrate). Almost 90 receivers have been completed, in more than 15 countries. Check out the receivers. Build one if you dare: 

https://soldersmoke.blogspot.com/search/label/DC%20RX%20Hall%20of%20Fame 

BTW — I own a Dymo machine, and my SSB transceivers are in wooden boxes made from junked packing material. 73 Bill N2CQR

F6GUH: True Homebrew

 

Philippe put it this way:  "Radio is my religion, my shack is my church." 

20 Meter transceiver

40 Meter Transceiver

80 meter transceiver

Today I was on 17 meter SSB, talking to Yannick HB9TWY.  He looked at my QRZ page and said that he had a friend with rigs that look like mine.  "Who is that?" I asked.  Philippe F6GUH is the intrepid homebrewer.  I like the looks of his rigs.  And they are truly "rigs."

Thanks Yannick.  And thank you Philippe. 

A Tale of "Ten Minute Transmitters" and "Tuna Tin Twos": N2CQR Goes Back to CW QRP!

Inspired by K1OA and KA4KXX, I put the SolderSmoke DC receiver to work on the CW portion of 40 meters. At first I used a very (perhaps overly) simple "Ten Minute" transmitter. On June 4, 2025 I worked N2WJW in New Jersey. But the transmitter drifted as it got hot. So I switched to the more robust Tuna Tin 2 (TWO transistors!) and worked W2XS in NY and N9FGC in Indiana on June 5. With both transmitters I was "rock bound" -- crystal controlled. Power out was always less than 200 milliwatts. Antenna was a low to the ground dipole. The receiver was powered by our beloved 9V battery. The transmitter had a second 9V battery. Some observations: First, even if you CAN hear other signals, the different tones allow your brain to seperate them out (this has long been known to CW operators, but might not be readily apparent to newcomers). So even if the DC receiver is broad in frequency response and even though it IS also receiving the other side of zero beat, you can make CW contacts (unless, of course, another station is on a frequency that produces exactly the same tone as the one you are trying to work), even at very low power . Second, you don't always really have to be right on the other station's frequency. Here's why: If he is looking he can see you in his waterfall! So that SDR waterfall is now a friend to crystal-controlled HDR operators. Who would have thought? Above is a picture of the my station with the Ten Minute transmitter. See the notes I wrote on the QSO with N2WJW.

Ten Minute Transmitter (the gray thing is a CW key)

Direct Conversion Receiver

Tuna Tin 2 that replaced the Ten Minute Transmitter

Note battery and crystal

WWII Homebrew In Norway

 

Go to amateurradio

r/amateurradio•14 hr. ago

steeljoo

How My Grandfather Tuned Into London During WWII with a Radio He Built in Secret

General

My grandfather was a lifelong radio enthusiast and ham radio operator. In his early twenties during World War II, he lived in the remote mountain village of Hjerkinn, working at the railroad station high above the treeline when Germany invaded Norway.

He joined the resistance movement and built radios using parts from a downed Luftwaffe aircraft—mainly the radio tube, as seen in the photos I’ve attached. With it, he secretly tuned into broadcasts from London. It was a risky and courageous act, but it kept him and others informed when access to truthful news was critical.

Later, he introduced me to the world of radio. As a kid, I spent hours scanning ham bands, police channels, and even unencrypted cellphone calls. I was probably way too young to be listening to some of it, but in the pre-smartphone era, it felt innocent enough. That early exposure sparked a lifelong passion for electronics and radio—one that still defines me today.

A few weeks ago, I visited my mom and saw one of the wartime radios he built. I thought this group might appreciate it—not just as a relic, but as a story of ingenuity, resistance, and the enduring magic of radio.

Thanks to Jim VE1KM for alerting us to steeljo's story. I told Jim that that Nazi tube is reminder of just how dangerous this all was for his grandfather. 

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.