How they Make Raspberry Pi 4 Single Board Computers

So, if the Raspberry Pi is a key part of your new "homebrew" rig, how much of the rig did YOU actually build? 

Germany: Direct Conversion Receiver Success!

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 (below) 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!  

 

Canadian Build of the Direct Conversion Receiver -- Do This in Your Town! (Video)

This is so cool.  We have been getting reports from Daniel VE5DLD up in Regina, Saskatchewan, Canada.  Daniel is a teacher and he has been building the receiver with a group of students.  

They have been doing very well.  They may end up having more success than we have had here.  

This morning Daniel fired up his build of the receiver and it was inhaling 40 meter signals.  You can hear the CW and the FT8 and you can also hear shortwave broadcast signals just above the 40 meter frequencies.  Congratulations to Daniel!  He is now one of very few radio amateurs who has homebrewed a receiver.  I think his students will soon do the same.  

Daniel's students have built several of the boards and appear to be on the brink of full success.  

Their PTOs look very nice. 

The AF amps were the most challenging of the boards.  Theirs look great.  Excellent soldering. 

We want the receiver project that we carried out at our local high school to serve has a model for others.  After all, we got our inspiration from Farhan in Hyderabad.  We want to see this kind of homebrewing continue.  All of the information on this receiver is on our Hack-A-Day.io page: 

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

We strongly encourage others around the world to find ways to use this project to teach analog electronics.   We think the circuit strikes the right balance between simplicity and usefulness -- when they are done, the students will have a useful receiver capable of worldwide reception.  

Please let us know if you are building this receiver; we are especially interested in the use of this receiver in student-focused group-build projects.  

"Ham Radio Ireland" June 2023 edition (and Free Propagation Guide)

 

Get the latest edition here: 

 https://www.docdroid.net/VlSXkrD/crnews0623-pdf

Thanks to Steve Wright EI5DD.  I had the great good fortune of running into my friend Michael EI0CL on the 17 meter band recently.  Mike mentioned that he had been talking to Steve.  So Steve is in good company.   

Steve also sent me a useful Solar Indices Data Card, suitable for lamination.  You can download it here: 

http://soldersmoke.com/Solar Indices Data Card.pdf

Can you ID this Receiver? Grayson Finds a Homebrew Receiver in Germany. From the GDR. Circuit? Schematic? Thermatrons?

 

Grayson Evans KJ7UM (the author of  Hollow State Design) was recently in Germany where he spotted this museum display of a homebrew receiver built in the GDR (the old East Germany) around 1983 by a 13 year-old.   Very cool. 

Here is today's task for SolderSmoke:  Can you provide any more info on this receiver? The card indicates 0-V-1 which would be a regen with no RF amplifier, right?  Maybe something like this: 

https://www.qsl.net/pa2ohh/15tuberx.htm

 Look carefully at the pictures and try to gather any additional information on the receiver or its builder.  

Thanks Grayson! 

George Heron N2APB talks about Coherent CW at FDIM: Interview #7 by Bob Crane W8SX

It was great to hear George's voice again.  I was a big fan of his "Chat with the Designers" podcast. And it was great to see that Pete Eaton WB9FLW (an old friend of SolderSmoke) was also involved in this presentation.  

At FDIM George was talking about Coherent CW.  Now, my views on CW have been made quite clear, but I am going to deliberately avoid snide comments about how Coherent CW might be a contradiction in terms.  Thank you.   I think this is something that Pete N6QW and I can agree on. 

Nevertheless, this is all technically interesting.  This reminds me of what happens with WSPR.  But I wasn't quite sure what George was getting at with his discussion of the phase of the incoming signal -- I can see the need to get the receivers' narrow filter exactly on the transmitting station's frequency, but why the phase?  

Here is Bob Crane's interview with George: 

http://soldersmoke.com/N2APB23.mp3

And here are a couple of things with background info on CCW. 

https://www.sigidwiki.com/wiki/Coherent_CW

http://www.arrl.org/files/file/Technology/tis/info/pdf/7509026.pdf

Thanks George, thanks Pete, and thanks Bob. 

Farhan VU2ESE FDIM Interview (#6) by Bob Crane W8SX: VHF Rig, sBITX, and Good News on Raspberry Pi 4

It was great that Bob was able to catch up with Farhan and talk to him about his VHF rig and about the sBITX. 

    

Farhan said that the VHF rig (the BITX23) was presented at the homebrew show-and-tell as a project.  The idea was to encourage others to get into VHF homebrewing.  Farhan points out that many of us are reluctant to go into VHF building, thinking that we need special or exotic test gear. No true says Farhan.   He is trying, with this rig, to bust this myth.  FB.

    

On the sBITX, Farhan points out that he too -- coming as he does from the homebrew tradition -- finds some of the modern rigs quite intimidating.  So he designed the sBITX to be less intimidating.  It is, he says, a tinkerable rig that could be homebrewed. It is all open source.  

    

Farhan points out that the rig is built around the Raspberry Pi 4, a device that has recently been hard to obtain.  This has driven up the price of the sBITX a bit.   But good news:  Farhan says that the word on the street is that the Raspberry Pi 4 will be available in quantity starting at the end of June.  

Here us Bob's interview with Farhan: 

http://soldersmoke.com/VU2ESE23.mp3

BITX23 VHF Rig

And here is a video of Farhan describing the BITX23: 

https://soldersmoke.blogspot.com/2023/05/farhan-describes-his-new-2-meter

Thanks Fathan!  Thanks Bob! 

Rick Campbell KK7B at FDIM: Interview #5 by Bob Crane W8SX

/KH6

Having recently been involved in an effort to teach students about radio electronics, I found Rick's comments especially interesting.  

At FDIM,  he and his daughter were presenting a hidden transmitter hunt using rigs and Yagis at 432 MHz.  This was in part the result of his students having wanted to do something new with ham radio.  It was very impressive that the students had done this all with gear that they had built themselves.  Rick also made sure that they all learned how to solder.   

Rick ended the interview with a nice shout-out to SolderSmoke. 

Here is the interview: 

http://soldersmoke.com/KK7B23.mp3

And here is a paper Rick did on VHF.  It is a bit old, but it is good.  

 http://www.pnwvhfs.org/conference/2009/Introduction-to-VHF-Experiments.pdf

 Thanks Rick!  Thanks Bob! 

Eric Schwartz WA6HHQ of Elecraft -- FDIM Interview #4 by Bob Crane W8SX (audio)

 

It was really cool that our correspondent at FDIM caught up with Eric Schwartz WA6HHQ of Elecraft.  Some highlights from the interview: 

-- Eric met Wayne Burdick through the NORCAL 40 (Wayne had designed it, and Eric was writing articles about it).  That was a very influential rig -- it was the basis for a book and a CALTECH course by David Rutledge. 

-- Elecraft has a strong QRP element in its DNA. 

-- The K2 is "Heathkit style" and offers the builder the opportunity to understand the rig at the component level. 

-- Eric says that using something you built yourself is worth at least 10db. 

Here is Bob's interview with Eric:  

http://soldersmoke.com/WA6HHQ23.mp3

Thanks Eric and thanks Bob.  

Jerry KI4IO (Wizard of Warrenton) Describes His ALL ANALOG Phasing Transceiver -- Bob Crane FDIM interview #3 (audio)

Wow, this one really resonated with me.  Jerry had me won over when, early in the interview, he described his decision to dispense with the Si5351/Arduino combo:  "I said the hell with this digital stuff!"  I hear you Jerry.  I feel your pain OM.  

Jerry then goes on to describe a rig with bits of circuitry from some legendary sources:  The Ugly Weekender transmitter.  SSDRA and EMRFD.  W7ZOI's 1968 Direct Conversion receiver.  

Jerry discusses the "presence" of the direct conversion receiver.  And he decries the pernicious effects of AGC.  (Indeed, real hams MANUALLY control the gain.) 

The Wizard of Warrenton then shares some important tribal wisdom:  After building that new piece of gear, leave it on the bench for a couple of weeks.  Beware of "radio infatuation" (what a great term -- we will have to include this in the lexicon).    Jerry points out that while at first, the new rig will seem just perfect, with time time the need for improvements and modifications will become apparent. 

Jerry also has connections to India and Nepal (where he helped Father Moran).  See: https://www.qrz.com/db/KI4IO

Here is W8SX's interview with Jerry: 

http://soldersmoke.com/KI4IO23.mp3

Thanks Jerry!  Thanks Bob! 

Greg Latta AA8V on Making Aluminum Chassis -- FDIM Interview by Bob Crane W8SX #2 (audio)

Our correspondent Bob Crane W8SX caught up with prolific builder Greg Latta AA8V.  Greg gave an FDIM talk on how to make aluminum chassis without having a machine shop.  I guess I am now going to have to buy a belt sander from Amazon.   

I was really glad that Greg mentioned his real passion: retro building.  FB Greg.  I have talked to Greg several times on the ham bands -- it is always an inspirational experience.  

Here is Bob's interview with Greg: 

http://soldersmoke.com/AA8V23.mp3 

Here is Greg's pdf file on his aluminum chassis construction technique.

https://www.frostburg.edu/personal/latta/ee/chassis/aluminumchassisconstructionnomovies.pdf 

And here is Greg's amazing web site: 

https://www.frostburg.edu/personal/latta/index.html

Thanks Greg!  Thanks Bob! 

Hans Summers G0UPL and his new QMX: The Bob Crane W8SX FDIM Interviews Part 1 (audio)

http://qrp-labs.com/qmx.html

We are very pleased and grateful to present this year's series of Four Days in May interviews by our FDIM correspondent Bob Crane W8SX.   Once again Bob did an outstanding job interviewing the FDIM participants. 

In this interview, the amazing Hans Summers talks about his latest QRP Labs kit, the QMX.  It is a combination of the QCX Mini and the QDX.  

Hans explains the M:  QMX. The M is for Marriage. Magnificent. Merger. Marvelous, many things like that. It’s what you get when you marry the mechanical and conceptual design of QCX-mini, with the SDR, multi-band digital implementation of QDX. Simply: QDX + QCX-mini = QMX. 

It has a very clever switching power supply that automatically adjust to prevent spurs and harmonics from the power supply from appearing in the band of interest. 

I was especially interested in his plans to implement an SSB option in future software updates.  Hans will use the same very complicated SSB generation scheme used in the trueSDX rig, but hopes to achieve higher performance and  improved signal quality due to the much more robust hardware of the QMX. 

Here is the interview: 

http://soldersmoke.com/G0UPL23.mp3

Here is the QRP Labs site about the QMX:  http://qrp-labs.com/qmx.html

Here is the QRP Labs web site: http://qrp-labs.com/

And here is a really wonderful and very current article by Hans on the evolution of QRP Labs and its rigs from 2010 right on up through 2023 and the QMX.  It is really interesting: 

http://qrp-labs.com/images/qmx/docs/fdim2023.pdf

Thanks to Bob Crane W8SX, Hans Summers G0UPL, and all of the FDIM organizers. 

Hans G0UPL-- Homebrew Hero