An Evening Bandscan on 40 Meters using the High-School Direct-Conversion Receiver

This video shows how useful this receiver really is.  Build one of these!

Listening to 40 meters on the DC Receiver -- And I Heard a Distinguished Homebrewer!

I made the video above to show postential builders how useful our Direct Conversion receiver really is.  Late in the video (starting at 11:17), I heard a station calling CQ.  It was N4QR.  A check of QRZ.com shows it was Bob Null.  Here is picture from Bob's QRZ page: 

Check out the old general coverage receiver and -- wait for it -- the homebrew thermatron transmitter.  TRGHS. 

Google led me to this amazing video by Stever N4LQ that describes a book that N4QR put together on how to build thermatron transmitters from Junkbox/Hamfest parts: 

Steve N4LQ is in contact with Bob N4QR and asked him which transmitter he was using when I heard him.  Bob said he thinks it was his 30 watt 807 final transmitter. 

Thanks Bob. and thanks Steve!

"The Build Is the Initiation" -- KQ4AOP Offers Encouragement and a PTO Coil Form for Receiver Builders

Scott KQ4AOP put a comment on a recent SolderSmoke Blog post that I found especially encouraging and apprportiate. He was writing about his experience building the High School Direct Conversion receiver.  

Scott wrote:

"This was my first receiver build and, it was great fun. When you finish the build and prove you are able to tune through the band, you are welcomed into the secret society! The build is the initiation. I am happy to print and ship the PTO if needed." 

The 3d printed form for the tuning inductor is often a show-stopper for prospective builders.  Scott offers to print out a form for you, and send it to you. 

Scott's mailing address is on his QRZ page.  His e-mail address is: streez55@gmail.com

 Thanks Scott! 

Here is a post I did early this year on Scott's receiver: 

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

Here are the SolderSmoke Posts about this project  (keep scrolling -- there are 41 posts!):

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

My Receiver Doesn't Work Right! What Should I Do?

An early version of our DC receiver.  Note the tuning guide under the grey tuning knob. 

We prepared this for use by the high school students who were building direct conversion receivers. Unfortunately none of them got to the point where they would use this little article, but given the fact that a number of people are now engaged in direct conversion receiver projects, I thought it would be a good idea to post this here. Also, much of this applies more generally to receiver problems. 

My receiver doesn’t work right!

What should I do?

First, relax.  You will be able to get it to work.  The design is good, people around the world have built this receiver, and you will be able to get it to work.  But homebrew radio is not plug-and-play radio.  Sometimes a new receiver needs some tweaking, peaking, and coaxing. 

Realize that the 40 meter band has its ups and downs.  The downs usually come at mid-day.  The sun’s position high in the sky causes a build up of the D layer of the ionosphere.  This tends to absorb radio waves. So signals are often weak at mid-day.  Signals will be much stronger in the morning, and in the evening.

Can you hear the “band noise” when you connect your antenna?   This sounds like hiss or static.  Some of this is the result of thunderstorms in Brazil.  Some of it is from events far away in the cosmos. Some of it comes from the weed whacker down the block!  But if you can hear this noise, that is a very good sign that your receiver is working.  The signals you are looking for will be stronger than this band noise.

Where are you tuning?  Your receiver tunes from about 6.8 MHz (with the screw all the way our) to about 7.8 MHz (screw all the way in).  But we are only really interested in the ham frequency band between 7.0 MHz and 7.3 MHz.  Try to tune your receiver near the middle of the tuning range (with the screw about half-way in).  You should hear morse code from about 7.0 to 7.06 MHz.  Then you should hear strong digital signals at 7.074 MHz.  Tuning further up (screw going in) you should start to hear hams speaking to each other using Single Sideband.   At first they will sound like Donald Duck.

 Don’t worry about the Donald Duck speech!  Just carefully tune through the signal until you hit the spot where the speech sounds normal.  You may have to tune up and down a bit until you find the right spot.  Now you can listen. 

 If you tune further up you will hear Shortwave Broadcast band AM signals.  You will be able to tune them in.  Sort of.  But they will sound distorted.  This is unavoidable with this kind of receiver.  But you will be able to hear the hams on Single Sideband with no distortion.

Sometimes you will only hear one side of the conversation.  That is normal.  The other station may be either too far away from you, or too close to you.  You may be outside his or her skip zone.

One very obvious thing to check:  How is your battery?  Is it drained, or is it still at about 9 volts?   You may need to change it.

How is your antenna?   It doesn’t have to be fancy or elaborate.   33 feet of wire will do.  But it does need to be up in the air a bit.  And you need to have the 33 foot counterpoise wire connected to the ground (on the PC board).  With many pieces of consumer electronics antennas are kind of optional – the devices will often work without them.  Not so with ham gear.  Antennas are important.  If you are not receiving signals,  it may be because of your antenna.

Challenge Accepted! Why we Designed the High-School Direct-Conversion Receiver the Way we Did

Dean KK4DAS's Beautiful DC Receiver

The folks over at Ham Radio Workbench have graciously accepted the challenge issued in our last podcast: that they scratch-build homebrew the 40 meter Direct Conversion receiver that Dean KK4DAS and I designed for local high school students.  We want to help our brothers over at HRWB.  For example, we may be able to supply a few of the 3D printed PTO coil forms.  Here is some background information on the project. 

Details on the project can be found here: 

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

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

Design Decisions in the Direct Conversion Receiver

Why did we do it this way?

In thinking about how to design this receiver, we had to make early design decisions on almost every stage.  Here are some of our key considerations.

VARIABLE FREQUENCY OSCILLATOR:

Normally we might have used a variable capacitor to change the frequency of this oscillator.  But variable capacitors are now expensive and hard-to-source.  Our friend Farhan in Hyderabad used a simple variable inductor for this purpose in his “Daylight Again” transceiver. The coil form for this part could be 3D printed.  A metallic screw would vary the inductance as it is screwed in and out of the coil.  

We also decided to use the same simple Colpitts oscillator circuit used by Farhan in his own high school direct conversion receiver.  This circuit is unusual in that the feedback capacitors are also the frequency determining elements (along with the variable inductor).  This simplified the circuit and reduced the parts count, and proved to be remarkably stable.

For the VFO buffer we used the simple JFET buffer from Farhan’s Daylight Again design.  

Based on suggestions from other radio amateurs, we developed a simple frequency readout based on the position of the end of the tuning screw  (how far in or out?).

We selected the 40 Meter band for this receiver because we thought it would be easier to get the VFO stable on this frequency, and because Farhan had built his receiver for 40 meters.

MIXER:

At first we hoped to use a simple singly-balanced mixer using two diodes and a single trifilar transformer.   But we found unacceptably high levels of AM breakthrough (mostly from Radio Marti on 7335 kHz) when using this circuit.  So we switched to a diode ring.  This required two more diodes and an additional trifilar transformer.   We believed the students would have great difficulty building and installing two trifilar transformers so early in their building experience.  So we used transformers that had been wound in Hyderabad by a women’s collective employed by Farhan, and developed a scheme for fool-proof installation of these transformers.

We also found that the mixer needed a diplexer at its output – this would provide a 50 ohm termination at all frequencies and would result in much cleaner action by the mixer and greatly reduced AM breakthrough from Radio Marti.   We used the same circuit used by Roy Lewellen W7EL in his Optimized Transceiver circuit.

BANDPASS FILTER: 

This was the simplest board in the project but it required the students to wind two coils on toroidal cores.  A simple dual-tuned circuit design would be sufficient.  We used component values from the QRP Labs website.  We showed them how to wind the coils, and made a video about the technique.  Students used a simple Vector Network Analyzer (Nano VNA)  to tune the filter.

 

AUDIO AMPLIFIER: 

We had to make several design decisions here.  First, we rejected the idea of using an IC amplifier like the ubiquitous LM-386. We wanted this to be a completely analog and discrete component experience. Then we rejected the idea of using a push-pull output circuit.  While this would have eliminated the need for an audio output transformer, it would have resulted in a more complicated circuit.  In the end we opted for three simple RC-coupled common-emitter amplifiers with an audio output transformer.  There was no feedback in these circuits.  We found there is a lot of gain (hFe) variation in the 2N3904 transistors that we used.  Care needs to be exercised in making sure that transistors of moderate (but not too high) gain are used.  

This AF amplifier chain probably presented a 1500 ohm impedance to the mixer (instead of the desired 50 ohms), but we think this problem may have largely been taken care of by the diplexer.  

We found some very small (one square inch) speakers that could be easily used in this circuit.

ANTENNA:

While the students could use a wide variety of antennas, we recommended a simple ¼ wave antenna with a ¼ wave counterpoise.  We thought that this antenna – of only 33 feet in length would provide good performance with low complexity, and would be well suited to the “upper floor bedrooms” from  which many of the students would be listening.  Also, this antenna would not require the use of coaxial cable or an impedance matching transformer. We made a video on how to build and use this antenna. 

POWER SUPPLY:

We opted for the use of 9 volt batteries.  This proved to be a safer and wiser choice that limited the kind of mayhem that could occur should a variable voltage supply be used.

Details on the receiver can be found here: 

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

May 29, 2023

A 40 Meter Direct Conversion Receiver from M0NTV -- With some SolderSmoke Comments

Nick's video appears above. 

First, let me say FB Nick.   It is nice to see you making use of the AGC amp designed by Wes and Bob,  using the board from Todd's Mostly DIY RF, using a mix of homebrew pads and Me-Squares  from Rex, and finally the Franklin Oscillator that we spent so much time talking about on SolderSmoke.  

But here are some comments:  

-- I still don't think you need that RF amplifier in front of the mixer. And I suspect you would be better off without it.  We did not use one in our high school 40 meter project, and never missed it.  In fact, on one version of the high school receiver I even put in a simple 10k pot as an attenuator (no RF amp).  Even up on 20 meters, I do not have an RF amplifier ahead of the diode ring mixer on either of the Mythbuster rigs I have built.  Nick,  maybe experiment a bit more and try the receiver just going from the BP filter into the mixer and see what happens.  

Note that Wes W7ZOI DID NOT have an REF amp ahead of the diode ring mixer in his original 1968 40 meter Direct Conversion receiver (the one that launched the solid-state DC recevier revolution): 

-- The Franklin oscillator is an interesting, but complicated circuit.  The gimmick is, well, gimmicky.  Here is the thing:  You can achieve similar levels of stability using simple conventional, single transistor oscillators.  We dispensed with the variable capacitors, and used PTO--style variable inductors. They worked fine.  This Franklin oscillator still does seem to drift a bit, right?   I would ground the board to the inside of the metal box.    

I would also try putting all the stages on a single ground plane.  This might help.  

Tezukuri and Chappy Happy -- Amazing Videos on Homebrew Radio (from Japan?) - Another 40 Meter Direct Conversion Receiver

So around the time we were building 40 meter direct conversion receivers, someone else was doing something similar.  His product (above) is a lot nicer than ours.  He has an S-meter and a digital frequency readout.  But like ours, his is built on a wooden board.  FB OM.  

If you want to see what a direct conversion receiver can do, watch his video (above). 

I was really amazed to see him use a modified VFO from a Kenwood TS-820.  Not long ago Pete N6QW spotted one of these on e-bay and recommended that I buy it.  As with the Yaesu FT-101 VFOs, we bought it for the gears and reduction drives but ended up with the entire VFO circuit.  I now have one on my shelf, ready to go.  TRGHS. 

We are not sure who Chappy Happy is, but "Tezukuri" means "hand-made" in Japanese. The writing in the video descriptions are in Japanese, then Chinese. 

Here is the YouTube channel.  Amazing stuff here:  https://www.youtube.com/@chappyhappy3675  He is clearly a ham.  He even works on an old S-38.  Who is this guy? 

The Rad Receiver from N6GWB

Geoff N6GWB and his eldest have produced a really wonderful receiver, and have joined the elite ranks of those who have built their own receivers.   Congratulations to both!  ( Be sure to watch the video below.)

Geoff writes:

Though I built it, my eldest has retained naming rights.  Behold the Rad Radio Receiver, an Soldersmoke inspired build.  It’s a 40m DC reciever.  I had planned on making this a truly 50-50 N6QW N2CQR build, but I needed to get it done for a show and tell this Wednesday.  I have N6QW dual JFET RF amp and mixer modules.  I have the N2CQR ceramic ocillator circuit from the 2017 DC receiver project.  I had planned on including the all analog audio amp from the more recent N2CQR DC project, but alas, time got the best of me.  I was hoping to make the whole thing all-analog.  (I thought the all analog would get me more “hard work” kudos at the show and tell.) I ended up including a LM386 audio amp making this a bit of a cyborg.

I have included pictures of the receiver open and closed.  The closed pic includes bespoke decals.  I have also include a brief movie demonstrating the audio.

Many, many thanks for the inspiration and knowledge!

Geoff

N6GWB

Scott KQ4AOP Successfully BUILDS a Receiver (Video) -- This is the Homebrew Spirit at its Maximum

This is just so cool.  Scott KQ4AOP has successfully homebrewed a ham radio receiver.  He used the circuit Dean and I developed (with a lot of input from Farhan and others) for the High School receiver project.  But Scott has had more success than any of our students.  And I think he has had -- in a certain sense -- more success than any of us.  After all, how many of us can say -- as Scott can -- that he used a homebrew receiver that he made to listen -- for the very first time -- to amateur radio signals?  Scott writes:  "Those first sounds were my first time ever hearing any Amateur Radio first hand!" 

In the email below, you can see Scott's deep commitment to homebrew: "I want to build my own gear for 40m. I want to learn morse code. I want my first contact to be on my own gear."  Wow Scott, the building of the receiver is the hard part, and you have already done that.  I think you are well on your way.  

In the video above you can watch Scott tune the entire 40 meter band and a bit beyond. You hear CW at the low end.  Then FT-8.  Then SSB.  Up just above the top of the band I think you can hear our old nemesis Radio Marti.  And this powerful broadcaster is NOT breaking through on the rest of the band.  FB Scott.  Congratulations.  

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

 Bill,

Thank you for the quick response, direction, and pointers. I won't give up, and I am not in a rush. 

I have wanted my amateur radio license since the early-to-mid-80s. I got my Technician and General in May of 2022 and completed my Extra in May 2023. I always wanted to understand how to design circuits, and I wanted to build them. I share that background to say that I have this impractical goal that I am stubborn enough to stick to (all due respect to you and Pete's advice on the topic of getting on the air). I want to build my own gear for 40m. I want to learn morse code. I want my first contact to be on my own gear. So, your blog and podcast really resonates with me. 

I am only teaching myself at this point. It was the perfect project for my goals. I thought that if all these high school kids in Virginia, Canada, and Germany can do it, it was the sweet spot I was looking for. 

The only transceiver I have was recently gifted to me. It is a Sommerkamp TS-788DX CB radio that allegedly works on 10m in addition to CB. I haven't connected it up because I wanted to stay focused on the HSR. I have a mentor who has gear that I can use to test the oscillator. I am not involved with the nearby ham club, but I know they would help if needed. 

Thanks again and I will keep you posted,

73 Scott KQ4AOP

KQ4AOPFebruary 2, 2024 at 10:49 PM

Bill and Dean - Thank you for sharing and documenting this receiver. I greatly appreciate you publishing the circuit, class notes, and build videos. That got me 75% to completion.
I feel blessed that both of you chipped in and encouraged me through the troubleshooting to finally getting the receiver to start “breathing RF”.
Those first sounds were my first time ever hearing any Amateur Radio first hand!

First Light! First Signals received on Version II of Homebrew 15-10 Transceiver

Ianis S51DX in Slovenia was the first call sign heard. Some peaking and tweaking remains to be done, but the receiver is working.

Congratulations to Scott KQ4AOP who got his Direct Conversion receiver working yesterday, And congratulations to Armand WA1UQO who got his regen receiver working. I think all of us are following Farhan's advice and are taking some time to just listen to the receivers we have built ourselves.

Mattia Zamana's Amazing Direct Conversion Receiver

Thanks to Ed KC8SBV for sending me this awesome video.  It looks like Mattia built this receiver way back in 1995.  The tuning indicator is very cool, and I had not seen a similar indicator before (could this be a way for us to escape the clutches of the San Jian counters or the Arduinos?)  The Italian ham magazine articles are great, and you can follow the rig description even if you can't read the Italian.  The pictures in in the attached drive are also very good.  

WB9ZKY used Google Translate to get English versions of the articles.  Thanks Chuck! 

https://www.dropbox.com/scl/fi/kil3osilchqlyk8afim2r/part1.pdf?rlkey=9ubgaqb8t4k91d1a10su9mw1p&dl=0

https://www.dropbox.com/scl/fi/t2790qatf5riepyqh5oj1/part2.pdf?rlkey=bhs77gkcchziakh7ngjbpuaz7&dl=0

I have been in touch with Mattia via YouTube:  He reports that he has done other electronic projects, but he considers this to be the most interesting.  He does not have a ham license -- he has a Shortwave Listener license.  His father was a ham:  I3ZQG. 

This is one of the rare cases in which the builder should -- I think -- be issued his ham licence purely on the basis of this build.  

Mattia writes:  

Jul 25, 2023 ITALIA

Self-built Direct Conversion Radio Receiver for the Amateur Bands 80 - 40 - 20 - 15 meters. This direct conversion receiver for the hf radio amateur bands was designed and built by me way back in 1995. Later, in 1996, it was published in two parts on RadioKit Elettronica magazine. What you hear in the video was received with a simple antenna made from 4m long wire inside the house. By connecting the receiver to a suitable antenna tuned to the various bands, the reception is truly excellent and no different from commercial professional receivers. This is undoubtedly the project that has given me the most satisfaction in my activity as an electronic hobbyist. For those interested in making it, here is the pdf of the project (italian language): https://drive.google.com/drive/folder... Here, instead, there are some photos: https://drive.google.com/drive/folder...

Mattia Zamana

Bringing a Faulty Herring Aid 5 Receiver Into the Light -- Fixing the AF Amp Schematic Error (video)

I picked up this old homebrew receiver in March 2023 at the Vienna Wireless Society's Winterfest Hamfest.  It is a Herring Aid 5.   I was surprised to see that the builder (who was he?) got the windings on the VFO transformer right.  Later, I learned that he had also substituted MPF-102s for the original Radio Shack FETs called for in the QST article. This allowed him to overcome the PC board layout problem at Q5 (VFO).  With an MPF-102, he was able to get Q1 working by kind of shoe-horning the leads into the proper holes.  FB OM.  Whoever he was, he seemed like a really competent builder.

The Hamfest Herring Aid 5

But then I started wondering:  Did he also overcome the big problem in the audio amplifier?  You see, there is an egregious error in the QST schematic.  Between the collector of Q3 and the base of Q4 (the two AF amplifiers) they have a 10uF capacitor to ground.  That would send most of the audio to ground. This is clearly a mistake.  Not only does it not make any sense, but this cap to ground does not appear in the PC board drawing, nor in the photograph that went with the QST article.  I included this cap in my 2014 built of the Herring Aid 5, but with it, I found the receiver to be exceedingly deaf.  When I clipped that capacitor out of the circuit, my 2014 Herring Aid 5 sprang to life.  Did this hamfest Herring Aid 5 have the error capacitor?  Would it too be brought into the light by clipping one lead?  

Sadly, the erroneous third capacitor was there, and it was wired into the circuit.  The receiver worked,  but just barely.  It was very deaf.  You could not hear 40 meter band noise, and you could barely hear strong CW signals.  Builders may have thought that this was normal with such a simple receiver. 

3 10uF caps. The center one is an error.  I have clipped it out

In the video above you can see what happens when I cut the lead to the mistake capacitor.  Suddenly, you can hear band noise, and CW signals.  The receiver comes to life -- for the very first time!  

This was an error that echoed through the decades.  As far as I know there was never a published errata.  The erroneous capacitor is there in the 1977 ARRL book entitled Understanding Amateur Radio.  In 1998,  NORCAL QRP redid the Herring Aid 5.  Incredibly, THEY INCLUDED THE OFFENDING CAPACITOR in their new and improved schematic.  

NORCAL's 1998 Schematic included C14

I'm fixing up this old receiver a bit.  It was nice to have it playing 40 meter CW yesterday.  Better late than never.  

This morning I was feeling kind of guilty about paying so much attention to a receiver from 1976.  But then I opened the paper and read about the recent find of a DeLorean car.  Heck if a DeLorean from the early 80's is worthy of attention, so is a homebrew receiver from the late 1970s. 

A Big Error Discovered in the 1976 QST "Herring Aid 5" Article (After 47 Years)

Click on image for a better view.  See arrows for Q1, Q5 and the parts list.

I tried as a teenager to build the Herring Aid 5 direct conversion receiver from the July 1976 issue of QST.  I could not get it to work. Important points: 1) I was attracted to the fact that this receiver used only parts available from local Radio Shack stores (I bought them) and 2) The article provided a PC board pattern (I also bought ferric chloride and etched a board). 

Looking back, I concluded that I had failed to get the VFO to oscillate.  I remember hearing signals when I tuned my HT-37 transmitter (on Cal, on 40) near the receiver.  I was very close, but I never got that Herring Aid 5 VFO to oscillate.

Thirty-eight years later I tried again to build the receiver.  Important points:  This time I used mostly junk box parts and Manhattan-style construction (no etching).  Still I could not get the VFO to work.  ZL2DEX spotted a problem -- I had wound the L6 and L7 coils with the wrong "winding sense."  I corrected this, and BOOM! the VFO sprang to life.  I assumed that I had made a similar "winding sense error" way back in 1976.  This, I thought, explained my failure to get the receiver working.  The QST article had warned that proper phasing of L6 and L7 was necessary.  I figured that I just hadn't fully understood what "proper phasing" meant.  So it was, I thought, all my fault.    

 

Here is the PC board pattern from QST.  Arrows show Q1 (DGS) and Q5 (DSG).  

But it is the same kind of FET!  Click on the image for a better view.

But then on October 17, 2023 a comment appeared on the SolderSmoke YouTube channel.  Rick WD5L had also -- back in the late 70's -- tried to build this receiver.  He recently looked closely at the recommended parts list (that we used!) and at the QST PC board pattern (that we also used). AND HE SPOTTED AN IMPORTANT ERROR IN THE QST PC BOARD PATTERN.   

Take a look at the pattern for Q5 above (see arrow).  That is the VFO FET.  A Radio Shack 2035 FET has a DGS pinout (see below).   The Gate is the center pin.  If you put this transistor into the PC board pattern above you would definitely be grounding the Gate.  There is no way the VFO would work under these circumstances.  Note too that the only other RS 2035 FET in the receiver is Q1 (the RF amplifier).  In the PC board pattern above Q1 is marked correctly as DGS.  This confirms the error in the Q5 PC board pattern.  There is no way an RS 2035 transistor can simultaneously have two different pinouts! 

Wow.  So this failure to get the VFO working may not have been my fault after all.  I may have actually gotten the transformer winding correct, but even if I did, there is no way this VFO would have worked using the part called for by QST and the PC board pattern shown above.  As a teenager I just did not know enough to spot the error or the inconsistency.  I kind put blind trust in QST.  I just couldn't get the thing to work.  

Rick searched the QST archives to see if they ever put out an errata on this.  So far, nothing. Worse yet, the scan of the PC board pattern on the QST site is very unclear and may have the pin designations on Q5 scratched out. This would make it more difficult to spot the problem.  (The image above is not from ARRL.  It is from a high quality scan of the original QST article done this week by a fellow Vienna Wireless Society member.)  Please let us know if you find any kind of errata or any acknowledgment of error.  

This is really pretty bad.  This was a project aimed at novices.  Far from encouraging homebrewing, this type of mistake is the kind of thing that would push people away from the soldering iron.  

Ironically, I may have been doomed by opting to use the QST PC board.  If I had used Manhattan-style construction (as I did in my more recent build) I would not have fallen victim to this PC board pattern error.  Also, if I had built this thing stage-by-stage (as we always now recommend) I would have more clearly realized (back in 1976) that the problem was in the VFO stage.  But I was 17 and didn't know.  I put blind faith in the QST article.  It never occurred to me that something in print could be wrong.  This realization came much later. 

There is more to talk about on this ill-fated project. In future posts I will discuss another error, this one in the AF amplifier.  And possible additional errors...  And I'll write about the 1998 resurrection of this project by NORCAL QRP and the New Jersey QRP clubs.  

Thanks to Rick WD5L for spotting the PC board error. 

The Super Islander Mark IV -- A Cuban DSB Transceiver Made From CFL Lightbulb Parts

Trevor Woods also sent us this report from Arnie Coro.  It is not clear to me what difference (if any) there is between the Super Islander Mark IV and the Jaguey Five (described yesterday).  But the bit about using parts from old CFL bulbs is interesting.  This was something championed by Michael Rainey AA1TJ several years ago.  See: https://soldersmoke.blogspot.com/2009/01/soldersmoke-98.html  

and:

https://www.qsotoday.com/transcripts/aa1tj

April 2010:

Today, I will be answering a question sent by listener Bruno from Croatia... Bruno picks up our English language programs via Internet, but he is now also listening on short wave too. He sent a nice e-mail message asking me about the latest version of the Super Islander amateur radio transceiver, because he wants to build one.

Well amigo Bruno, the Super Islander Mark IV is now on the air, and results are very encouraging considering that it is a 40 meters band transceiver built using recycled electronic components.

The Mark IV uses a totally different approach to the receiver design, and it adds two solid state audio filters.

Amazing as this may sound, some of the electronic components used to make the Super Islander Mark IV transceiver came from the circuit boards of broken or damaged Compact Fluorescent Light Bulbs... and that means that there is virtually an endless supply of those parts.

Here is now amigo Bruno, and amigos listening to the program at this moment, a brief description of the Super Islander's Mark IV receiver module.

It starts with a simple resistive signal attenuator that feeds a dual tuned bandpass input filter.

The filter has a limited bandwidth , chosen so as to limit response to out of band signals... The filter is followed by a cascode transistor radio frequency amplifier stage, that feeds a broadband four diodes product detector.

Low level audio from the product detector goes to the audio filtering and amplifying module, made with discrete transistors, of which several of them are also recycled from the Compact Fluorescent Light Bulbs circuit boards...

This version of the Super Islander, the Mark IV , is radically different from any previous ones, as we have now switched over to a totally low cost solid state design , that can be easily reproduced because it uses very common electronic components and straightforward , easy to adjust circuits.

In our upcoming mid week edition I will describe the VFO, or variable frequency oscillator and the transmitter module of this unique low cost amateur radio transceiver, the Super Islander Mark IV... about the lowest possible cost transceiver that will make possible regular two way ham radio contacts on the 40 meters band using either voice or radiotelegraphy modes.

Sam WN5C Builds a Michigan Mighty Mite and Takes it to Lake Thunderbird

 

Sam WN5C built a Michigan Mighty Mite and then went the extra mile by putting it on the air from a field location.  And what a great name this location has for a QRP operation:  Lake Thunderbird. 

Sam wrote up his experiences for K4SWL's QRPer blog: 

https://qrper.com/2023/05/guest-post-lake-thunderbird-k-2792-with-a-homebrew-transmitter/  

Below is a picture of the rig.  NOTE THE LOW-PASS FILTER.  FB OM. We wouldn't want that rig tearing up the electromagnetic spectrum. 

Looking ahead, Sam writes: 

Next step is a DC receiver (maybe the high school receiver?) and then a more substantial transmitter married together, I think. This is all incredibly fun.

Thanks Sam! 

Nine Homebrew Transceivers by Walter KA4KXX (and some QRP and QRO RC planes)

 

Our friend Walter KA4KXX in Orlando recently sent us this really cool "family photo" of his homebrew rigs.  Be sure to see the key that explains the photo (below) FB Walter.  Thanks too for the model airplane pictures. (Click on the images for better viewing.) 

Walter wrote: 

I recently realized that I am now operating nine homebrew transceivers, which would fit nicely in an “aerial” photograph, so I grabbed my stepladder and everything did fit well in the frame.  Six of them come from the BITX side of the family, with #1 and #7 direct conversion and #9 a single conversion superhet but using the NE602.  More basic information is included in the sketch.

I tried a Si5351 VFO once in the dual-band rig #4, but by the time I built the QRP Labs kit with so much closely-spaced soldering, and then added sufficient filtering and amplification to properly drive a 50 ohm load, I was exhausted!

These nine were created during the past eight years, and were preceded by eight more transceivers that I can document, but those have all been disassembled, with many of the parts being used in these later rigs.  I build my transceivers to be operated often, and since 20 Meters has been hot lately, for example, my POTA Hunter log shows over 300 CW and SSB contacts in 2023 alone, so rig numbers 7 - 9 have been earning their keep lately.

In summary I have created a lifetime total of seventeen transceivers so far, and although I am nowhere near the fifty-plus tally of Pete N6QW, I did spend a lot of years instead homebrewing many radio-controlled model airplanes of my own design.  Two photos show one example that I flew in the 2011 Blue Max Scale R/C Contest at the Fantasy of Flight Museum in Polk City, Florida against some stiff QRO competition.

—Walter KA4KXX

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.  

Farhan Speaks to Students about Satellites and Direct Conversion Homebrew Receivers (audio)

In our talks at the local high school we have frequently mentioned Ashhar Farhan, his Cubesat experience, and his use of a direct conversion receivers teach electronics to students in Hyderabad, India.  So we were really please to have the opportunity to bring Farhan himself in to speak to the students we have been working with.  

Here is the audio of Farhan's talk: 

http://soldersmoke.com/FarhanTJ.mp3

The acoustics in the room are not great, so you may have to listen carefully, but it is worth it.  Farhan dispenses a lot of tribal knowledge and wisdom about satellites and about the value of homebrewing simple radio equipment. 

Farhan and Bill Fire up the sBITX and (at the other end of the tech spectrum) a Direct Conversion Receiver (video)

At the high tech end: the sBITX.  At the low tech end: The high-school direct conversion receiver. 

Check out the frequency readout on the DC receiver!