Farhan Talks LARCSet (CW & SSB) at FDIM (with a Lot of Homebrew Wisdom)

Watch the presentation here: https://www.youtube.com/watch?v=MefojjQ84YY

Farhan made it to FDIM 2026  (he must hold the "distance travelled" record!). We thought he might be talking about the latest version of the digital SDR sBITX, but NO!  Farhan talked about the entirely analog LARCSet, a 30 dollar SSB/CW monobander.  And in the process he shared a lot of good homebrew history and wisdom. I took notes on the video of his presentation: 

-- Farhan recounts his discussion with Steve Hartley, President of GQRP.  Farhan said he started to talk about SDR projects, but Steve steered him away from all that.  Farhan said he realized that the homes of GQRP members are often small, and projects need to fit into took boxes that are pulled out as needed.  There is often not even enough room to mount a screen.  Analog rigs just fit better.  

-- Farhan talked about the beauty of analog.  He also shared some info on the recent timeline of analog rigs, going back to 1976 with the IARU gift kits made available by W1VD.  Farhan very kindly mentioned the DC receiver that Dean and I are promoting.  He talked about the 2003 BITX 20 rig, and the subsequent uBITX.  Farhan talked about the cleanliness of all-analog rigs.  "SDR's are a mess!" he said. "With SDRs it is difficult to avoid hash." 

-- Farhan said he had trouble measuring the phase noise of the VFO in the LARCSet.  He consulted with Wes W7ZOI.  Wes told him this was NOT a measurement problem; VFOs have almost no phase noise.  The level is even lower than that of crystal oscillators.  Of course, crystal oscillators are more stable, but they also have more phase noise.

-- He noted that almost no recent homebrew design does not rely on an Si5351.  This, he said, is "not a healthy situation."  Indeed.   

  --  Farhan talked a bit about how Indian regulations seemingly require a deviation from the completly open source ethos.  Indian regs require companies to have assets.  So the PC board layouts have to remain proprietary.  

-- Farhan talked about the sharpness and shape of the BP filter in the LARCSet.  I remember talking to him about the shape of my BP filters in my dual banders -- I had to rebuild the filters.

-- On the crystal filters that form the heart of SSB rigs, Farhan noted that cheap low Q crystals often introduce a lot of loss in the filters (that may explain my problem with some styles of computer crystals). 

-- A member of the FDIM audience asked about the Sharpie written frequency readout on the LARCset that Farhan showed to the group.  Farhan told them that this was the only frequency readout used in the rig. 

  -- With the LARCSet, Farhan used varactors to vary the frequency.  But the varactors he used were cheap but horrible.  They varied the frequency as the rig hearted up.  The LM386 was the source of heat.  He also noted that the cheap varactors, while cheap, did not provide linear frequency readout. Farhan said the varactor scheme was still not perfect; he offered a PTO solution that could be used instead.  Three cheers for the PTO! 

-- Farhan said the LARCset was really an SSB rig, but when coming to FDIM he said he felt obligated to present a rig that included CW, "or they would throw me out of the room."  Farhan described a scheme to generate CW based on what was done with the Atlas rigs. 

-- Farhan said the LARCset might even work on 2 Meters.  Hmmm.  

-- On tuning, Farhan said he used a very large tuning dial (he said it was like a steering wheel) and then recommended the use of a smaller control that could serve as an SSB "clarifier." 

-- Farhan pointed out that homebrew rigs are never really done; even decades later, they can still be modified.  

Watch the presentation here: https://www.youtube.com/watch?v=MefojjQ84YY

Rick N3FJZ on the Red Summit Podcast with Charlie NJ7V

 

Check it out! 

https://www.youtube.com/watch?v=sUQA2uNskEs

I liked Rick's story about his early days in radio electronics.  Taking old TVs from the street -- been there, done that!  FB Rick, 

Rick points out that he has never used a commercial ham radio rig, so he is unfamiliar with some of the "features" of such rigs.  Sometimes, I think, the lack of experience is a good thing. 

I really like the display that Rick uses, showing the operating frequency, the VFO frequency and the BFO frequency.  This might help with our struggle with those who complain that we are 40 Hz off.  Rick then notes that he used 15,000 lines of code for this display.  Wow, that shows the benefits of being -- like Rick is -- both a real software wizard and a hardware wizard. 

Rick describes how  he uses tin-plated steel boards in lieu of copper clad boards.  

I liked his approach to schematic drawing -- we benefited from this in the SolderSmoke Direct Conversion receiver project. 

When Rick talks about taking pieces of schematics from other rigs and making them work in new rigs, Charlie notes that, "this is the ham radio way."  Exactly. 

There is a lot of really sentimental stuff in this podcast.  SolderSmoke is mentioned frequently.  They mention Pete and Dean.  This starts at around 22 minutes. Rick talks about Farhan at around 26 minutes.  And he talks about Wes W7ZOI.  

Rick talks about some of his early projects.  I have a sentimental attachment to his Lakeside DC receiver: 

  

Then, a few years later, we had our first HB2HB contact.  Homebrew rigs on both sides:  

https://soldersmoke.blogspot.com/2015/10/hb2hb-n3fjz-n2cqr-si5351-and-bitx-tias.html

Finally, I agree with the last sentiment expressed by Rick in his conversation with Charlie:  The Red Summit podcast -- especially with its focus on homebrew -- is exactly what this hobby needs.  Anything that encourages hams to experience the fun of homebrewing is a good thing.  Three cheers for Rick and for Red Summit. 

How VU2RM Got Into the Satellites

 

Readers will remember last week's post about the homebrew rivalry between VU2RM and VU2NR. (Note the bio about VU2RM below).  This morning Farhan sent me this article from a 1970s-era Indian ham radio magazine in which VU2RM describes his early efforts to get onto the satellites. I also tried during the mid 1970s, but I didn't have the kind of magic decoder ring provided (via QSL!)  by OH2RK.  My satellite success had to wait some 20 years, until I was in the Dominican Republic.  More on this below the VU2RM article. 

This morning I replied to Farhan's email:  

Very cool Farhan.  I see that Pete may have an Indian rival for "most SSB transceivers built."  

I got into the satellites during my 1992-1996 stay in the Dominican Republic.   At first, we had no way to get the up-to-date Keplerian elements to predict satellite passes.  Then Compuserve opened up. I had to telephone Miami from the DR to get the Keps.  I ran up a huge phone bill. 

I too built an antenna for these contacts.  Mine was the 2 meter portion of a 144/440 MHz project from 73 magazine called "The Ray-Gun".  I built mine out of scrap lumber and refrigerator tubing.  I still have these elements!  I used them in the beam that I built to listen for YOUR satellite!   In the DR, elevated the thing by 45 degrees and pointed it in the general direction of the satellite.  

RS-11 had a very cool robot aboard.  If you called it just right, it would issue you a serial number.  I have the QSL.

Here are some articles about our satellite adventures.  

https://www.gadgeteer.us/ASTRO.HTM

BTW, Luis Ernesto HI8LEZ visited me during summer 2024 in the DR! 

My hombrew 2 meter beam in the Dominican Republic

Early SSB in India: Espionage, Stolen Secrets, and Kleptomania

 

Earlier this month I had stumbled across a 1964 QST article entitled "A Sideband Transceiver, VU2 Style."  I forwarded the link to Pete N6QW, Grayson KJ7UM, and to Farhan VU2ESE.  Last night Farhan sent me this insider look at early SSB in India.  It is really great.  The battle for preeminence among early SSB homebrewers in India reminds me a bit of Jean Shepherd's descriptions of homebrew radio in Hammond, Indiana.   Farhan's description of the early rigs being "all over the place, in about 3 or 4 boxes... with a whole lot of  wires running all over"  really resonated with me -- yes, even today, that is true homebrew. Thank you Farhan for sharing this with us. 

Farhan writes: 

VU2NR, Raju was a legend! Quirky, brilliant and liked to be by himself. He lived to a very old age of 100 or so. He was the first ham to get on SSB from India. Therein hangs a story of espionage, stolen secrets, cold war, politics and kleptomania. Most of the actors are now dead, so it can be told now.

I never met VU2NR, he rarely travelled. One evening at Paddy's shack, I was shooting the breeze with VU2RM, Ram, about my own SSB efforts. Ram was probably the most knowledgeable ham on SSB in India and his RM96 was widely duplicated. Paddy and Ram were trying to empty out a bottle of the Old Monk and I casually mentioned how we had to scrounge around for SSB lattice filters until Wes showed us how to build them ourselves. At that point, Ram unloaded this story to us:

VU2NR joined the Allies and worked as a radio mechanic with the RAF. After the war, he joined the ICAO (International Civil Aviation Organization) and then finally the United Nations as a comms expert, he was in Aden for a while. He understood the radios well and he became a well known homebrewer. His most brilliant work was the NR60 (it is an SSB radio built around four CA3028 kind of mixers). It was the first SSB radio that I had built (and it worked!) but we are getting ahead of ourselves.

Back in the 50s, ham shacks of India consisted of World War II surplus receivers and a self-built 807 transmitter driven by a VFO. There was a fair amount of buzz on the bands about SSB. The hams could occasionally pick up DX that was on SSB and easily resolved by the BC-348s  and the HROs but there was no way to build one. The QST was difficult to get your hands on but Raju had become a subscriber of the QST during his RAF days.

A QST sailed on a slow boat from the USA and landed up at the port on the east coast of India, Vizag and made its way to Raju's doorstep. Over weeks, he gathered parts and in the summer of 1955 he quietly came on 40 meters on SSB! This blew everyone away. Until now, one had only heard stories of SSB transmitters told by sailors of Sandra Maria Gracia after a few drinks to a bunch of hams clutching onto their 807s. It was as if Jesus had materialized!

VU2RM, Ram was not amused. He was a homebrewer with pride and honour. He could never be bested. He spent the next evening tuning on Raju's SSB up and down to note that the other sideband was missing and the carrier was gone. It sank into him that Raju had indeed beaten him to SSB. Ram worked at the Kakinada port, about 100 miles further down south on the east coast as the port radio engineer. He didn't sleep well. At 5 am, he got up, walked out and took a bus to Vizag where Raju lived. He was at Raju's door at 9 am. Raju was amused at the young guy and invited him in. They knew each other as rival homebrewers. There was tension in the air. Raju showed off his SSB transmitter in the front hall of his home. It was all over the place in about 3 or 4 boxes. There was the power supply, the PA, the ssb generator using a 2Q4 (a passive RC phasing network), a separate VFO box and a whole lot with wires running all over. In a corner was his stack of QSTs.

Raju's XYL called out for coffee and snacks (called 'Tiffin' in south Indian English) and Raju sauntered off to the kitchen to fetch his celebratory feast...

With alacrity and swiftness that only comes once in a lifetime, Ram, VU2RM, sprang to action. He darted to the QST collections, quickly found the one with the SSB transmitter on the cover, turned the pages to discover VU2NR's dog eared pages. He was staring at the circuit trying to memorize it. He realized that 2Q4's internal diagram had really odd values that he could never remember. So he did what James Bond, Bertie Wooster and Louvre thieves would have done. He rolled it up and slipped it into his pocket! (In those days, QST could be rolled and slipped into your trouser pockets, leading to wider dissemination of knowledge). He called out to Raju asking him to forget the refreshments as his bus was due back home. He legged it out and didn't stop until the bus stop. He hid around the bus yard hoping to not be caught by Raju. In the meantime, Raju, cursing the young upstart, drank both the filter coffee cups and left for work. Raju was unaware that the royal jewels were stolen.

VU2RM, Ram, started to work on his SSB radio over the next few days. He stopped going to work. At first, he figured out how to null the carrier using a twin triode modulator. Next, he fabricated the 2Q4 circuit. He sand papered lower value resistors until they read as close to the value as he could manage on his analog volt-ohm meter. He gave up on the exact capacitances and just soldered a bunch of the closest together. He had a crude 2Q4 equivalent. This, he dropped into his rat next circuit and an 'Almost' SSB signal emerged. He was probably having a sideband suppression of less than 15 dB at this point. It was suppressed and the carrier was nulled. He declared victory.

In the morning, Ram was on the band strutting off his SSB transmitter to the local gang. Graciously accepting the accolades from his fan club and extolling virtues of life on SSB to the lesser mortals. The news quickly spread over CW and AM of VU2RM as the second SSB station from India.

In the meantime, the atmosphere at VU2NR was tense. You could cut the air with a toggle switch. Raju had no idea how Ram had gotten the SSB. He carefully tuned around on his signal. He could pick up faint traces of the opposite sideband. Ram's carrier was also leaky. He decided that Ram was probably passing off his AM transmitter as a SSB. He said as much on air to his own devotees. Ram, ever watchful of his own reputation, heard this criticism and broke in, challenging Raju to prove that his was indeed not SSB. Raju's reaction was mixed. Now he wasn't sure. 

It was now Raju's turn to have a sleepless night. After his breakfast, he had had enough of confusion and he hauled his old scope and himself into the 8 am bus to Kakinada and showed up at Ram's doorstep! "Show me your radio" he said crisply.

For Ram it was his moment of crowning glory. He had brought Raju down to his shack! Raju plugged his scope into Ram's transmitter. He sniffed around the transmitter which was laid all over the table. "Where is your 2Q4?" he asked. Ram pointed to bunch of resistors and capacitors and Raju realized Ram's dog headed brilliance. He sat down, traced to the balancing pots (there would be two of them as this was a phasing transmitter). At this time, he decided to show Ram his greater prowess. He reached out to the carrier nulling pots, and tweaked them to minimum carrier (Ram was watching the oscilloscope with his mouth wide open). He told Ram that he had now fixed the carrier and then showed him how to adjust the RF phasing control for minimum by tuning to the opposite sideband on Ram's Bc 348. Having proved to Ram that he was a better homebrewer, he declared that now, Ram's transmitter was indeed SSB and not semi-AM. Raju retrieved his honor by being gracious and "mentoring" Ram.

 

They had coffee and snacks and it was time for Raju to leave, as Ram was showing Raju to the door, Raju's eye caught a QST on the shelf... he pulled it out and stared down at the QST with his own address neatly stickered on the QST's cover. He glared at Ram for a long time and turned away and left in a huff. Ram called after him down the street but Raju was gone.

VU2NR's last radio was built when he turned 90. It was the NR90 and it was built using NE612 chips. His hamming came to an abrupt end when one day his son dropped in unannounced only to find him perched on his tower of 30 feet height, fixing a fallen element of his self-made log periodic. The son was so horrified that he took away all the radios to save him from self-harm (this part of the story is unconfirmed).

 

My friend Sasi, VU2XZ, was close to him and he got the family to donate his callsign to a repeater that has been established in his memory. VU2NR lives on.

- f 

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

Here is the link to the 1964 QST article.   VU2NR's article appears on page 19: 

https://www.worldradiohistory.com/INTERNATIONAL/QST/QST-1964-03.pdf

"Rig Here is Homebrew" -- The Joys and Sorrows of Building your own Rigs

This is kind of a re-run.  I came across it today on YouTube and thought it was pretty good.  So here it is again.  

 -------------------

Dean KK4DAS asked me to speak to our local radio club, the Vienna Wireless Society.   It was a lot of fun.  I talked about my evolution as a homebrewer, some of the rigs I made, the moments of joy, and the tales of woe.   You can watch the presentation in the video above. 

I was really glad to be able to explain in the presentation the importance of people like Pete, Dex, Farhan, Wes, Shep and even Dilbert. 

I was also pleased to get into the presentation the N2CQR sign that Peter VK2EMU made for me.  Thanks Peter! 

Here is the URL to the YouTube video (also above): 
https://www.youtube.com/watch?time_continue=3414&v=VHSr-v4QO7Q&feature=emb_logo

And here are the PowerPoint slides I used: 
https://viennawireless.net/wp/wp-content/uploads/2020/06/VWS-presentation-Rig-here-is-homebrew.pdf

Ashish N6ASD's Beautiful SolderSmoke Direct Conversion Receiver -- Built in Bangalore -- "This was such a fun project. This was my first direct conversion build, and I learned a lot along the way."

Ashish N6ASD is a really good guy.  We started watching his projects when he was in San Francisco.  He does a lot of fundamental radio building.  And he is a friend of Homebrew Hero Frank Harris K0IYE. 

When I spotted a "thumbs up" from an N6ASD on the SolderSmoke Discord channel, I knew that we would soon have yet another Bangalore Direct Conversion Receiver.  Ashish has been in contact with both Farhan and Ramakrishnan.  FB. 

Ashish writes:  I finally finished building the receiver! This was such a fun project. This was my first direct conversion build, and I learned a lot along the way. The biggest challenge was finding stable capacitors for the oscillator. In my first attempt, I used whatever I had in my junk box, but those capacitors drifted all over the place. Mica caps seemed expensive and difficult to get in Bangalore. I ended up buying surface-mount NP0 capacitors instead. Soldering them was a hassle, but they are much cheaper and easier to get here. Next step will be more mods and experimentation! The first improvement will be in the BPF. I will replace the regular ceramic caps with NP0 caps and re-tune it.

Here is Ashish's receiver inhaling CW:   

Congratulations Ashish -- Welcome to the Hall of Fame! 

Ashish N6ASD

The resemblance between Ashih's photo and the famous

1818 painting by Caspar David Friedrich is completely coincidental,  

but quite remarkable. 

https://en.wikipedia.org/wiki/Wanderer_above_the_Sea_of_Fog

 

Ted KN4ZXG's FB SolderSmoke Direct Conversion receiver: "This project is the greatest gift to homebrewing..."

There it is, a thing of beauty.  The best part is that Ted built this receiver himself.  That is something that most hams NEVER do. 

Ted writes: 

This project is the greatest gift to homebrewing since I got interested in radio nearly a decade ago. Lot's of great projects out there but most go into a mysterious black hole of obsolete parts like the NE612 mixer that's hard to get, or even the LM386, which is plentiful but not as cool as this amp. Everything's divided neatly on it's own board and explained. The builder has wiggle room on the layout and ways to test each module whether that's with nice or budget equipment. Not only did I learn a ton about each stage, but also about making RF probes and making use of my modest but super useful equipment like the Nanovna. Although there were no mysteries, it all comes together to make magic. If you know stuff, you can do stuff! Thanks again de KN4ZXG, Ted.

While he has some great plans for modifications and improvements, at this point I think Ted should follow Farhan's advice and spend some time just listening to the receiver that he has built. Direct conversion receivers sound especially good. It is as if they are closer to the ether.

Here are some clips of Ted's receiver in action:

 

Congratulations Ted.  Welcome to the Hall of Fame.  

Honorable Mention: Andreas DL1AJG's THREE SolderSmoke Direct Conversion Receivers for Biologists

 

Andreas DL1AJG was another of those intrepid hams who,  in the dark of winter 2023 took up the SolderSmoke Direct Conversion Receiver Challenge in order to test our receiver (before we pushed high school kids to build it).  Andreas came to the task with a lot of useful teaching experience. At the time he was an academic  biologist and had been teaching a course called "Applied Electronics for Biologists."  See: 

https://soldersmoke.blogspot.com/2022/08/can-biologist-fix-radio.html

Some of Andreas's students

I put these receivers in the "Honorable Mention" category only because they deviated a bit from the basic schematic:  they used an indoor ferrite antenna, had an RF amplifier ahead of the mixer, and did not use a transformer in the AF amp.  But they are very clearly the SolderSmoke DC receiver, they succeeded in inhaling RF, and Andreas and his students built them to help us.  

Here is the schematic they used: 

Click on the image for a better view

Here is an e-mail exchange I had with Andreas when the scholatic dust had settled in June 2023: 

Dear Bill,

Please my apologies for my late update on our DCR project. We started with the course in the semester break and once the semester started only a handful of students were able to finish their receiver. A long shelf of shame .... 

Here is what we've got so far (those were finished at the end of April already). 3 nice DCRs completely sufficient to copy CW indoors without additional antennas starting from late afternoon. Strong stations can be heard all day. I found that coupling some 6m of wire with one or two windings to the ferrite core can boost the signal dramatically but can also increase noise. 

The PTO is based on your design (Bill Meara N26QR &  Dean KK4DAS) which was sparked by Farhan  (VU2ESE) , except that I've swapped the FET for a NPN. The input amplifier and antenna is from the JUMA active ferrite antenna by Matti Hohtola (OH7SV), the band pass filter is from Hans Summers (G0UPL), the mixer and the headphone amplifier is inspired by Pete Juliano (N6QW), you told me that the diplexer (as well as the whole DCR idea) is attributed to Wes Hayward (W7ZOI) and the perfect schematics of Rick Scott (N3FJZ) where crucial to get me started in the first place. I enjoy keeping track of original sources, as I would do in science. This shows that even little achievements are based on the ideas of many other great people -  and this is nothing to be ashamed of. 

This was a lot of fun! Thank You!

Best and yours sincerely,

Andreas

Wow, the direct conversion re-engineering of education continues, this time at graduate-school level with biologists in Munich!  Amazing.  

Andreas points out that his group was also plagued by semester-related problems that caused many additions to the German shelf of shame.  Let's hope that someday soon these builders will come to their senses and join the ranks of those who have finished their homebrew projects.  

Looking at the schematic (above) of Andreas's project, there are a couple of significant differences from ours:   

-- Their AF amp used a transformer-less push-pull design.  We had considered this but abandoned it thinking that it would be too complicated to explain the workings of this circuit to our students.

-- Most significant, is Andreas's use of a ferrite rod antenna and an RF amplifier.   I think a simple 33 foot quarter wave antenna (with a ground or a counterpoise) might work better.  But hey,  to  each his own!   The important thing is that a number of these receivers were successfully built.  They look beautiful.  

Congratulations to Andreas and the successful Munich homebrewers!  

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

Thanks to Andreas DL1AJG.  Welcome to the Hall of Fame.   

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

Join the discussion - SolderSmoke Discord Server:

https://discord.gg/Fu6B7yGxx2

 

Documentation on Hackaday:

https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver

 

SolderSmoke YouTube channel:

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

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

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

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

Ramakrishnan VU2JXN

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

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

Ramakrishnan writes:  

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

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

 get this working. The PTO is very stable.

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

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

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

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

and make simple modification to this receiver and improve it.

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

Here is some more video of Ramakrishnan's receiver: 

Congratulations Ramakrishnan. Welcome to the Hall of Fame! 

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

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

Juan LU2VJM's Beautiful Argentine SolderSmoke Direct Conversion Receiver

I was really pleased to see Juan LU2VJM's rapid completion of the SolderSmoke direct conversion receiver.  But I wasn't really surprised -- Juan is an experienced homebrewer who has successfully completed Farhan's BITX transceiver.  Juan and I talked about how it is worthwhile for even an experienced homebrewer to go back and build a direct conversion receiver.  Farhan did this.  Farhan said that we do this because we are tool makers.  We have opposing thumbs that allow us to grab a soldering iron.  Indeed.  And you can hear the happiness in Juan's voice when he says in the video, "Today we have reception!"  Excellent. 

I was also pleased to see this receiver enter the Hall of Fame becasue this marks our first receiver from Latin America.  We hope there will be many more.  

Here are some pictures of Juan's receiver during construction: 

Juan's AF Amplifier

Juan's Diplexer with homebrewed coil

Another shot of the AF amplifier

The mixer, getting ready for construction

The completed receiver. FB!

Thanks Juan!  And congrastulations! 

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

Nate KA1MUQ Turns His Frying Pan DC Receiver into a Double Sideband Transceiver and Works Idaho from California

Wow, you can see the look of homebrew satisfaction as Nate works Idaho from California with his homebrew Double Sideband Transceiver.  It is a good thing that Nate got that frying pan into the shack before he was banned from the kitchen. 

Nate writes: 

I finally got my DCR to be a DSB transceiver.  I had a lot of trouble with transmitted RF getting back in to the VFO and causing distortion.   While I imagine I could have tried putting the VFO in metal box, I instead opted to move the VFO to a 4.7-5 MHz range and then mix that with a 12 MHz crystal oscillator.  Now the VFO is at a frequency unaffected by transmit RF.  This mixer and crystal oscillator are on the breadboard and from SSDRA.  The transmit amplifier chain was taken from Fahran's Daylight Again radio.   I just got a 570 mile contact on 5 watts - conditions are good.   If there is interest let me know and I'll share my schematic.

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

I looked this morning and I have 100 DSB posts on the SolderSmoke blog.  There are lots of ideas there on how to homebrew for DSB, many of them from Cuba, many covering DSB rigs that I built in the Azores, and others that I used in the Dominican Republic.  Check it out: 

https://soldersmoke.blogspot.com/search/label/DSB

 

SolderSmoke Podcast #257 -- Wrap up of the SolderSmoke Direct Conversion Receiver Challenge

SolderSmoke Podcast #257 is available. 

Video version: https://www.youtube.com/watch?v=xOoZiHbC4Ag

Audio version: https://soldersmoke.com/soldersmoke257.mp3

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

 

SolderSmoke blog DCR posts:

https://soldersmoke.blogspot.com/search/label/TJ%20DC%20RX

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

Lot of success!   So far 22 completed receivers:   35 others are being built.200 or so people are on the Discord server. 

What a great achievement this is!  Folks are homebrewing receivers. 

Scott KQ4AOP heard his very first amateur radio signals through this receiver. FB!  

Lots of great ham homebrew spirit. NE3U, N9TD and others 3d printing coil forms for others.  FB 

It is not too late.  Dean's videos and the Discord server will remain up, even when we ourselves have moved on.  

Big Picture:   Farhan's Four Stages -- All you need to build a rig:  Oscillator,  Filter,  Mixer, Amplifier. 

Homebrew and Manhattan vs. Kit built with PC board.  We think Homebrew is a better experience. Dean recently assembled some Ikea kit furniture.  Does that make him a carpenter?  No.  

We do update the schematic as we learn.  This is similar to what happens to software.  Github?  Version 2.3?    In the old days, when QST came once a month, we lived a harder life.  We don't have to do that anymore. 

Let's talk about the boards one by one:  

The Oscillator (VFO or PTO): 

-- Started out as an amalgam of Farhan circuits:  We liked the very simple oscillator he used in his Hyderabad DC receiver project for the girls schools.  No need for a hard-to-find variable cap.  But we found we needed a 3.3 k ohm resistor in the emitter to make it go.   We took the buffer/amp from Farhan's "Daylight Again" circuit, but later (much later!) added a .1uF cap across the source of the J-310. 

-- With brass screw, not really a permeability tuned oscillator.  Brass has same permeability as air.  Works via Eddy currents.  But the screw thing is very reminiscent of the old Collins PTOs, so we call it a PTO.  And it IS s PTO if you used a steel screw.   You should study the doc in the mods section about how to modify the PTO.  Metalurgy matters! 

-- We used silver mica caps in the frequency determining circuits.   This is important. 

The Mixer: 

-- We started with a simple two diode, single transformer singly balanced mixer.  Only LO signal would be balanced out.  This would work, but we got a lot of AM breakthrough from Radio Marti, just above the 40 meter band.  So we went with a homebrew diode ring mixer.  

-- Important to unserstand how the diode ring really works:  LO just switches on and off the diodes.  Very cool that several builders sought to understand how diode ring works. 

-- Best way to test the PTO and the Mixer?  Put them together and look at the waveform at the mixer input.   Is it flat topping?  Then both stages are working.  

-- Diplexer: From QRP legend W7EL's Optimized QRP transceiver.  Seemed to help knock down Radio Marti.  But we kind of knowingly disregarded AF amp input impedance.  It would have been too complex to fix. We were going for simplicity.  

BP Filter:  

-- We actually got to do the NanoVNA test with one set of the high school students.  This was very cool.  Proves the worth of the NanoVNA. 

-- Again good to learn the theory. 

AF Amp:  

-- Kind of an amalgam of a Forest Mims amp and the amp from the Herring Aid 5.  

-- Sure, an LM386 would have been simpler. But we did not want to use ICs.  And IC AF amps oscillate too.  You learn more by going discrete. 

-- We used a transformer.  For simplicity.  We know the push-pull circuit, but wanted to avoid it. Some guys are going to other AF amp circuits becasue of the transformer. See this as an interim measure... You can fully meet the challenge later, when you get the transformer.   

-- We also -- in the name of simplicity -- did not use feedback amps.   We have an optional bandaid resistor across the oscillator to lower overall gain.  

-- It can oscillate.  But keeping leads short, keeping inputs away from outputs, putting adequate electolytics on the 12V power rail can prevent this.   This is a good lesson in good construction practices.  And with the real world of amplifiers (they all aspire to be oscillators!) 

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

Some Tales of Woe: 

• Simple mis-wiring – need to learn to  read schematics

• Transistors in backwards – importance of checking the data sheet for your brand – sometimes different brands of same part have different pinouts
• Lying Test Equipment
• Jay W3V3 unreliable measurements from old Fluke auto-ranging multimemter
• Phil, W1PJE – using a 10X probe with scope termination set to 50 ohms
• Peter, VK3TPM – faulty component tester (mixed up collector and emitter on NPN transistor)
• And many, many setup issues with scopes, signal generators, TinySAs, NanoVNAs
• Bad parts

 

Some “lessons learned” taken from the Walk of Fame Channel

• Wayde, VA3NCA – taking care when choosing junque drawer components, solidifying concepts introduce in the licensing material – benefit of hand-son experience “building them made them more real”
• Peter VK3TPM – don’t trust your transistor tester, transistors can pass signals even when wired backwards.  Importance of 10X probles.  NP0/C0G caps for frequency stability
• Ken, W4KAC – learned to better use his test equipment to trouble-shoot, and finally learning to trust his troubleshooting after changing out a faulty transistor.

Parts sourcing:  We were surprised at how much time people spent on this.  Parts sourcing struggle reminds us of the importance of 1) understanding the circuit and 2) having a decent junkbox. 3) scrounging old parts when necessary. 

Looking ahead:  Antennas are important! You probably can use Cat 5 cable instead of real coax.    Noise is natural.  Mods are fun. CW in some ways harder than DSB.  Lot of antenna info on the internet. 

You can modify the PTO for easier tuning.  See the doc. Add a front panel, or a case.  Once your basic receiver is done, you can experiment with better circuits.  See the mods doc for ideas.  

Final Comments:  

-- It is ultimately the builder who has to make the machine work.   Homebrew means that YOU the builder are going to make it work.  

-- Be careful about who you take advice from or give advice to.  Don't be afraid to say "I don't know."  Ask yourself:  Is the guy who is giving me advice really an experienced homebrewer?  Am I? 

-- We learned a lot in this process.  You guys have made this a better receiver. 

-- Be careful about starting over...  Bill and Dean's homebrew nightmare!