"The Magic That Only Comes from a Radio you Built Yourself" -- The Many Benefits of True Homebrew

 Receiver on the bottom,built around 1997. 

Transmitter upper right, built in 1993. Power supply upper left, 1998.  

Adventures on the road to HB

Homebrew Radios in the age of the Internet

By Bill Meara, N2CQR

MAGIC

"I listened to the magic that only comes from a radio that you built yourself." In that one sentence (posted to an Internet e-mail group), Mike, VE2GFU, nicely described the feeling that can arise in the midst of a room full of solder smoke... and the reward that awaits those who endeavor to build their own radio receivers. In an age of mass produced, homogenized, high price commercial equipment, there is still magic to be found in the production and use of simple homebrew radios. I recently put together my first superhetrodyne communications receiver - I had so much fun with it that I thought my fellow amateurs might be interested in the project.

I was a frustrated teenage radio builder....

When I put my first homebrew low power transmitter on the air a few years ago, I thought I'd maximized my ham radio satisfaction. I gleefully reported to other stations that "RIG HERE IS HOMEBREW". For a while, I really thought that my fun meter was pegged! But everytime I looked at the commercial receiver that sat alongside my QRP transmitter, I knew in my heart of hearts that I still had some work to do. The truth was that only half my station was homebrew. Until I built my own receiver, I would not be able to enjoy the warm glow of satisfaction that comes from running a completely homebrew station. As a kid, I'd always looked with wonder and envy at the exotic homebrew stations in the DX column of QST magazine. I wanted to do what those intrepid foreigners had done. I decided to finish the job. I decided to build a receiver.

"Receivers are Difficult!!!"

I approached the project with some trepidation. Since my earliest days in the hobby I'd heard that "receivers are difficult." There seemed to be a deeply believed and long-standing bit of conventional wisdom that said that most hams could sucessfully build transmitters, but receivers were somehow beyond our capabilities. During radio club meetings, old timers would share tales of homebrew adventures from days-gone-by. They told of tube transmitters built on chassis fashioned from purloined street signs. There were a lot of great stories, but they were all about transmitters. When I'd ask about receivers, the old timers would look a bit sheepish as they admitted that their receivers were all commercial.

Receivers are difficult. I knew from personal experience that there was some truth in this axiom. As a teenager I had tried to barge into the ranks of the homebrewers with an audacious attempt at reproducing a varactor diode-controlled receiver I'd seen in one of the ham magazines. I never got it to work. As I approached this recent receiver project, I think a desire for vindication - and a desire to finish the job I started in 1974 - was part of my motivation.

Barebones, no frills, one step at a time

The "Barebones Superhet" presented in a July 1982 QST article by Doug DeMaw seemed to be just what I was looking for. As the title imples, it is a very simple, easy-to-understand circuit. Most of the stages were built around discrete solid state components - no mysterious IC black boxes. 

Remembering my bitter defeat in my earlier receiver project, I decided to take a fool-proof approach to this one. I took Doug DeMaw's very simple schematic and made it even simpler by dividing it up into separate stages. I would build each stage one at a time, each on a separate printed circuit (PC) board. For my receiver there would be separate boards for the Radio Frequency Mixer, the Variable Crystal Oscillator (VXO), the intermediate frequency (IF) amplifier, one board for the Product detector/beat frequency oscillator (BFO) and one audio amplifier board. I would test each stage before going on to the next.

Parts acquisition in the age of the Internet

As a teenage wanna-be radio maker, parts acqusition had been a major problem. I'm happy to report that the Internet and Express mail services have largely eliminated the tortuous "waiting for the mailman" vigils that many of us endured back in the dark ages. I kicked off my project with a brief session involving several parts catalogs, my computer and a credit card. A few short days later, the boxes started coming in and actual construction was about to begin.

While the catalog houses provided many of the parts, my junk box, hamfests and fellow hams were the sources for many of the components. I think that this diversity of parts sources adds to the character of the final product. When I look at my receiver, I can see parts that came from my old friend (now SK) Pericle, HI8P. There are components in there that were sent to me by Tom, W1HET and several other ham friends. There is a reduction drive from an old Swan 240 and a grommet from a deceased Heathkit Luchbox. The LM386 audio amplifier chip (a concession to modernity!) came out of a Kanga Kits direct conversion receiver; I didn't have an eight pin socket for it, so I scrounged through my junk box, found a 16 pin socket and cut it in half. Like I said, this approach to parts acquisition gives the radio some character. 

Lunch time PC board design

My "one stage at a time" approach resulted in some special challenges and opportunities. I had to design the PC board patterns myself. For hams accostomed to using ready-made PC boards, or simply reproducing patterns made by others, this might seem like an intimidating task, but since I was dealing with only one stage on each board, it turned out to be easy and rewarding. I was using boards that fit very conveniently in the front pocket of my shirts. I made PC board design a lunch-hour project. I would go to work with my schematic and a couple of index cards in my pocket. I'd cut the cards down to PC board size and used them to plan the layout of the boards. I usually had to do two or three "drafts" before I was satisfied, but I found that I was able to do about one board per lunch hour. Doing the layout myself definitely added to the "I did it myself" feeling at the end of the project.

I set a goal of completing one board per week - most of the design and planning would take place during the lunch hours, most of the construction took place early on Saturday and Sunday mornings.

Testing, testing....

My arsenal of test gear is far from laboratory grade! I have a little (ancient) Eico 435 oscilliscope and an old Heathkit signal generator. I bought the scope for 25 dollars on the Internet. The generator was a 15 dollar hamfest purchase. The 'scope will only read up to about 5 Mhz, but since the IF of my receiver would be 3.579 Mhz, I knew it would be very useful.

Testing the stages was a lot of fun. The VXO and BFO were easy to test - I just listened for the signal on a Radio Shack general coverage receiver. For the IF AMP I used the signal generator to put some 3.579 Mhz energy into board and used the 'scope to make sure it was amplifying.

One of the most difficult parts of HF superhet construction is the IF filter. Doug DeMaw's circuit employed a three crystal ladder filter. Doug described it as simple and easy, but to me it looked a bit intimidating. One of the benefits of homebrewing is that you can really "have it your way". Wishing to avoid a frustrating battle with a complicated filter, I searched through the QRP/Homebrew literature for a simpler approach to IF filtering. I found what I was looking for in another article by DeMaw. In this cicuit he used one crystal with a resistor to ground. I decided to use this simple filter and put off construction of the more sophisticated (and narrow) three crystal circuit until later.

So I redesigned the RF mixer board to accomodate my simplified filter. I wasn't quite sure if this little foray into electrical engineering would be successful (my degree is in economics!) so the testing of this stage was tinged with some anxiety. I set the signal generator for the low end of the 20 meter band. I got the VXO oscillating and put the scope on the output of my simple filter. Slowly I tuned the generator across the 20 meter CW band. All of a sudden, at one very specific point, a big 3.579 Mhz signal popped onto the 'scope screen! Eureka! My mixer was mixing and my filter was filtering!

Holy cow! It really works!

After about a month and a half of this, I had assembled an impressive looking collection of small circuit boards. I couldn't resist putting them all together on the workbench to see if this thing would really receive. Armed with a set of alligator clip test leads I connected inputs to outputs. It was early in the morning and 20 wasn't really open yet, but it was Saturday and I figured there were some folks out there trying to coax the ionosphere into action. As I was checking the test leads, I started to hear - almost imperceptiably at first - CW. At first I thought the sound was coming from my Drake 2-B, but a quick check showed the Drake was completely off. My little creation was actually receiving radio signals!

As late afternoon rolled around I decided to see how my still incomplete device would handle SSB. As luck would have it, my crystal let me tune around 14.200 Mhz. There I found the very melodious tones of EA3OT. Echo Alfa Three Oooold Timer, with his "six over six over six" antenna system filled my shack with beautiful phone signals. My relatively wide, one crystal filter was ideal for reception of Mike's fine signal. There really was something quite magical about looking at my little collection of boards and realizing that they were receiving signals from far-away Barcelona. I was experiencing "the magic that only comes from a receiver that you built yourself..."

Enclosure (sort of)

Now it was time to start putting the radio in a proper enclosure. A few years ago, Paul Carr, N4PC, * (*Described in several editions of the CQ magazine during 1993) built a 40 meter solid state rig on a wooden base. Disliking metal work, I immediately appreciated the wisdom of this approach. Realizing that I'd probably want to add additional circuits later on, I decided to make the chassis about twice the size I really needed. A visit to Home Depot yielded a suitable (16"X11") piece of pine. I also picked up some very light sheet metal that I thought would help with the front panel.

I had three large double sided PC boards in the junk box. The circuit boards were attached to these PC "base" boards with some Radio Shack spacers and 4X40 screws. The Base boards were bolted to the wooden base.

I used the sheet metal to fashon an L shaed front panel. The material was not quite rigid enough, so (in keeping with a very old ham tradition of stealing radio materials frm the kitchen) I put a little "cookie baking sheet" between two layers of the Home Depot sheet metal. The L shaped panel was afixed to the pine base. A smaller L shaped piece of scrap aluminum was attached to the back side of the pine chassis - this would serve as the mounting point for the antenna and power connectors.

My creation was starting to look like a radio. Better yet, it resembled one of those impressive homebuilt rigs that I used to see in the DX column of QST. I felt I was getting close to membership in the that elite group of intrepid hams who had actually "rolled their own." I was starting to feel a kinship with all of those intrepid, creative wackos who build things in their basements or garages. I felt part of the same homebrew tradition that dates from in the early days of ham radio. Just like the guys who build small airplanes in their backyard shops, just like those guys in California's Homebrew Computer Club, I was approaching the point when I could begin sentences with the proud phrase, "I built..."

Debugging

But of course, I was not done yet. Not by a long shot. When you are homebrewing, you have to be patient. You have to start out realizing that you are definitely not involved in "plug and play" radio.  Very few homebrew receivers will work properly the first time you fire them up. The radio needs to be properly aligned. Amplifiers and oscillators need to be tamed. But I think this is one of the most satisfying part of the homebrew experience. It is during this phase that you really get the sensation that you are molding your creation to satisfy your requirements. You are physically molding it by deciding where you want the control knobs and external connectors. And (even better) you are molding it electronically by deciding how you want to to sound. It is during this phase that you really put electronic theory to work.

I had a few very common problems. My audio amplifier would scream like a banshee if I turned the gain up. My variable crystal oscillator was kind of sluggish - it sometimes wouldn't start up right away when I applied power. A preacher from the 22 Meter broadcast band urged me to repent every time fired up my new radio. And worst of all, 80 meter CW signals from the venerable W1AW jumped right over my receiver's front end filters, landing right in my 3.579 Mhz IF frequency. These signals not only appeared to be mocking my technical abilities, but they also seemed to be making fun of my code speed.  Like I said, this was definitely not plug and play.

In my effort to fix these problems, modern technology provided me with resource that was completely unavailable during my earlier (1974) battle with a superhet: the Internet. The 'net puts the radio builder in almost instantaneous contact with a worldwide network of entusiastic solder melters. I found the rec.radio.amateur.homebrew USENET group to be an excellent source of information, advice and moral support.

The internet can turn your homebrew project into a multinational enterprise. Hams from around the world chimed in with helpful hints. It was a lot of fun to encorporate suggestions from distant Australia into my little HB receiver. And it was very reassuring to know that all those far-flung Elmers were available if I got into a real jam.

I was particularly gratified when I got some e-mailed words of encouragement from the guy who had designed the receiver I was building, Doug DeMaw, W1FB. Doug's son had spotted one of my pleas for help in one of the USENET groups and had relayed my message to his father. Doug sent me a very nice and encouraging note. I was saddened to learn that shortly after our exchange he became a silent Key.

Solutions to most of my problems came very quickly - and I learned something with each of them.

The screaming banshee audio amp turned out to be the result of a simple circuit error - I'd failed to ground one of the bypass caps on the LM386 AF amp chip (the only IC in the rig).

The Variable Crystal oscillator was made more obedient by playing a bit with the values of the two capacitors that madeup the feedback network in the Colpitts oscilator.

The preacher and W1AW required a little more effort. I decided that I needed a bit more filtering at the front end of the radio. I could have easily just thrown in one or two more tuned circuits between the antenna and the mixer, but I was concerned that losses in these circuits would adversely affect receiver sensitivity. Roy Lewllan, W7EL, had advised me (via the net) to perform a simple check of receiver sensitivity: I was told to listen to the receiver output while connecting and disconnecting the antenna. If connecting the antenna resulted in a noticeable increase in the noise output of the receiver, there would be no need for additional front end amplification. My receiver was not really doing well on this test, so I was concerned that adding more tuned circuits at the front end would worsen the sensitivity problem. It seemed to me that a stage of RF amplification that included a couple of tuned circuits might help me banish the unwanted preachers and code practice sessions without further degradation of receiver sensitivity.

Doug Demaw's QRP Notebook pointed to a simple, grounded gate FET amplifier with tuned circuits at the input and output. I quickly put this stage together on its own small PC board and put it between my antenna connection and the mixer board. The amp was obviously amplifying, but it seemed to be getting carried away. Whenever I'd tune both the input and output circuits to peak, the amp would begin to oscillate. I turned to the Internet and aske for advice. Help quickly came from afar. A fellow named PK Singh sent me an email with the solution: I had to "tap down" on the toroidal coils in the two tuned circuits. This deliberately introduced impedence mismatches that effectively reduced the stage gain and thus stopped the howling. (A side benefit was a noticeable increase in tuned circuit Q - a big help in my battle with the 22 Meter station). With the tapped down amp in the circuit, my receiver passed Roy Lewellan's noise test with flying colors and I was no longer the subject of harrassment from 22 meters and W1AW. Viva el Internet!

Coffee can frequency readout

My frequency readout scheme needed some work. The tuning capacitor I was using had a little venier reduction drive built into the cap. This made for very smooth tuning, but it made it impossible to work out any kind of frequency readout on the front panel. I had to peer over the panel and look at the variable capacitor to determine where I was in the band. In an age of multidecimal numeric digital readout, I was clearly behind the times.  And my neck was starting to bother me. 

To upgrade, I found a junkbox 365 pf variable cap with no built in reduction drive. This was about twice the capacitance that I needed, so I simply plucked out about half of the rotor plates. I also found a Johnson 6:1 reduction drive in a junker Swan 240 transceiver. With a piece of scrap aluminum, I engineered a little mount for the capacitor. The Johnson drive allows for the attachment of a frequency readout dial. I found that the top of a coffee can (the metal part you always throw away) was ideally sized for my front panel. Soon I had the modified cap, reduction drive and coffee can readout dial mounted on the front panel. A triangular piece of electrical tape provided a sharp looking pointer. A few pieces of masking tape on the coffee can top served as frequency markers. I realize that my "coffee can readout" will seem incredibly crude to those accostomed to glowing numerals, but I get a real kick out of it every time I spin that little homebrew mechanism.

Filter Finale

In a certain sense I was done. I was able to pair my new receiver with my QRP transmitter and was easily able to make QSO's. I was working European stations regularly with 3 watts out. But my simplified crystal filter was a too wide for serious CW work. I could hear several CW signals simultaeously and - worse yet - I could hear the "other sideband" on the stronger signals. So I hadn't really achieved the coveted "single signal reception" status that is - after all - one of the main reasons for going the superhet route.

There are a number of excellent article out there on the design of CW crystal ladder filters. Unfortunately the building of these filters requires the use of some special test gear to determine the electrical charecteristics of the particular crystals that will be used.

Wishing to avoid the construction of test gear that would be more complicated than my radio, I decided to simplify filter construction. I bought a bag of 50 3.579 Mhz TV color burst crystals from Dan's Small parts. I then built a simple Colpitts oscillator circuit on a Radio shack breadboard. I tuned my Drake 2-B receiver to 3.579 Mhz and started plugging crustals into my breadboard oscillator. I screened out those rocks that were signficantly off frequecncy, then I went through the pile again, judging by ear (using the tone from the Drake 2-B) to select three crystals that were very close in frequency. (I know that a frequency counter would have made this easier, but I don't have one so I had to "make do.")

I simply pugged these crystals into the filter circuit described in Doug DeMaw's 1982 article. Essentially I was "hoping for the best", hoping that the characteristics of my rocks would not be significantly different from those employed by Doug DeMaw.

It all worked out very well. The new filter significantly sharpened my receiver's selectivity. I could no longer hear strong signals at two points on the dial. Single signal reception had been acheived!

My filter proved to be far to sharp for confortable SSB reception, so I worked out a little switching arrangment that allowed me to switch between my original (wide) filter and the new, sharp CW filter. MISSION ACCOMPLISHED

I found that my technical skills improved dramatically during the course of this project. I even noticed a marked impovment in manual dexterity. By the time the receiver was finished, I was much more confident about putting together my own circuits. In order to be truly "100 percent homebrew", I needed to whip up a power supply for my station and a sidetone oscillator for my transmitter. These projects were quickly completed and I was soon on the air with a 100 percent HB station.

Homebrew is good for you! It really doesn't matter what band or mode you build for, a homebrew radio will provide a kind of satisfaction unavailable from store-bought units. A project like this will improve your skills, expand your knowledge and will put you in league with all of those intrepid inventors who have turned piles of parts and wires into devices that magically extract signals from the ether.

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

More details on this homebrew rig here: https://soldersmoke.blogspot.com/2022/09/fixing-up-old-homebrew-rig-barebones.html

Mike WU2D's Video on the SimpleX Super Receiver -- Part II

 Another FB video from Mike WU2D.   

But you know,  I too find myself kind of opposed to front panel on-off switches.  I power my rigs with small DC supplies.  I just turn on the supply when I want to use one of the rigs.  I don't have or need a switch on the front panel of the rig.  

I especially liked Mike's use of the gate dip meter and, of course, the Q meter.  FB OM. 

I must say I have a preference for the first version, but only because I dislike the regenerative circuit in the second version.  I do like the newer-style coils -- I have one in the BFO of the Mate for the Mighty Midget receiver.   

Thanks Mike for the sideband inversion factoid in Part 1!   The Hallas Rule -- words to live by. 

One word of caution.  I used 6U8s on my Mate for the Mighty Midget receiver.  I had good results, but WA9WFA had a lot of trouble.  We eventually concluded that the 6U8s didn't age well.  And they were quite long in the tooth.  We found (from the tube guys) that 6EA8s aged better and were a good and easy sub for the venerable (perhaps TOO venerable) 6U8s.  I switched tubes in my rig and it did seem to work better.  BTW, this is the receiver that I use to listen to the Old Military Radio Net on Saturday mornings.  

Here is the story of our switch from 6U8s to 6EA8s: 

https://soldersmoke.blogspot.com/2022/02/6ea8s-in-mate-for-mighty-midget-and.html

SimpleX Super Superhet Receiver -- A Great Video from Mike WU2D

Here is another great video (and project) from Mike WU2D.  I'm a big fan of homebrew superhets.  And wow, Mike presents a band-imaging superhet!  Two bands for (almost) the price of one!  I have FIVE homebrew dual-band band-imaging transceivers around me.  Believe me, once you have the experience needed to build an SSB transceiver, a dual-bander is the way to go.  Five bands seems like a bit too much.  But two seems to be at the sweet spot.  

I wrote to Mike reminding him to talk about the sideband inversion problem.  This rig will invert the 75 meter signals,  but this is easily resolved by just shifting the BFO frequency.  I also pointed out that many of today's builders will be detered by the need to scrounge for parts.  Where oh where is the BOM OM? 

Thanks Mike! 

Pil Joo's Homebrew Superheterodyne Ham-Radio Receiver

It is just very cool to see someone build a superhet and get it to work.  For so many years amateurs were told that "homebrew receivers are too hard."  Even simple regens or direct conversion rigs were sometimes seen as beyond the abilities of amateurs.  But here we see another reminder of this not being true.  Even a superhet -- which is a lot more difficult than a direct conversion receiver -- can be homebrewed by an amateur builder.  Three cheers for Pil Joo! 

He wrote on the SolderSmoke Facebook page: 

I finished my first super het receiver. It's for the 40m band. It consists of: bandpass filter, tuned amp, diode ring mixer, wide band amp, crystal ladder filter, wide band amp, then SA602 + LM386 combo. I learned tons as i put all the components. First two amps are my design. The third amp is bga2866. The bandpass filter is what i posted a few days ago. I planned to make another one but with 2.5db insertion loss i thought it was good enough.

The result is actually quite good. I can hear everything a local kiwisdr can hear. Now, I have lots of ideas about how i can improve, but that will be another radio.

Pil Joo

Basic Radio Circuitry -- a 1971 film

This 1971 training film is pretty good.  I like how they break the RF circuitry into just four components, then describe the AM receiver stage by stage.  The way they handle diode (envelope) detection is exactly right.  But their description of how mixing moves the incoming signal from the broadcast band to the IF is overly simple, and sort of just repeats the hetrodyne story from music. Real mixing is, of course, more complicated than that, but too complicated for a 15 minute film. 

Homebrew Receiver -- AG5VG's 20 Meter "Mythbuster" Receiver

Michael has the receiver done and is wisely heeding Farhan's advice about pausing to enjoy the homebrew sounds.  

I was pleased to see someone else using the FT-101 VFO.  Great piece of gear.  

On to the transmitter!  

AG5VG's Homebrew 20 meter Superhet (with a CW rig Coming) (Video)

 Michael AG5VG finished this receiver last weekend.  He hopes to build a CW transmitter using an output of the Si5351.  Obviously I defer to Pete on that one.  Good going Michael.  I think it sounds great and looks even better.  

CuriousMarc Visits Cape Canaveral -- Lots of Space History (and some ham gear)

I like all the CuriousMarc videos, but I especially liked this one. Marc and company visited some of the very early launch sites and bunkers at Cape Canaveral.  If you thought Apollo tech was crude, take a look back at what they used in Mercury and Gemini.  Wow.  

I spotted two ham radio receivers.   In the first bunker at 10 minutes 28 seconds we see an old National HRO Sixty with the classic HRO dial, much like the one given to me by Armand WA1UQO. (Thanks again Armand!) Note how they attribute one of the early launch disasaters to two diodes in the power supply that shorted due to launch vibration.  I hate it when that happens.  

In the second bunker we see a Hammarlund HQ-140 at 19 minutes 7 seconds.  This was apparently being used as a Frequency Standard (or maybe a time standard?) perhaps receiving WWV at 10 MHz.  I note that the frequency knob shows it set for the AM broadcast band... 

Charlie ZL2CTM's New Receiver

It is truly a thing of beauty.  

I really like that variable capacitor.  (Where did that come from?  How can I get one?)   

Charlie's calculations on each of the stages is -- as always -- really nice.  

I like the J-310 infinite impedance detector,  Charlie's use of solder wick,  the wooden base, and his decision to keep the circuitry visible.   

I also like Charlie's decision NOT to put that VFO in a metal box.  Too often we see projects that try to convince us that the receiver just won't work unless everything is hermetically sealed in submarine-like boxes.  Not true!  And Charlie's receiver demonstates this.   

Charlie is clearly keeping up the Kiwi tradition of fine homebrewing exemplified by the Tucker Tin 2,  ZL2BMI's DSB rig,  and many other FB HB projects from ZL. https://soldersmoke.blogspot.com/search?q=New+Zealand+DSB

Thanks Charlie!  Be sure to check out the rest of his YouTube channel: https://www.youtube.com/@CharlieMorrisZL2CTM

Justin's Receiver -- A 40 meter Superhet from AC8LV

 

FB Justin!  I really like the board that you are using as a base for the project.  And you have some great mentors in Nick and Loren.  

It is wonderful that you have that receiver working.  But I would tweak and peak quite a bit before taking on the transmitter.  Get a decent outside antenna -- even a dipole or a 1/4 wave with counterpoise would be a big improvment.  Like this one:  

https://soldersmoke.blogspot.com/2023/03/an-antenna-for-high-school-direct.html

And try to square away the grounding on the board (maybe some copper tape from Amazon) and the power supply you are using (I hope it is not one of those noisy wall warts).  When  you are experimenting, it can be useful to power varous stages with 9V batteries -- this is a good way to find out where noise is coming from.  If your AF amp is squealing at 12 volts, you need to break the feedback loop that is leading to oscillation.  Often the feedback is through the power supply.  Finally, try to get that homewbrew crystal filter working -- if the bandpass is uneven, you just need some impedance matching at the input and output.  

Great work Justin!   Keep at it.  73  Bill 

Bill,

I am sending video and pictures of my 40m  superhet that I built. I have it on the floor in an extra room in the house. The antenna is a stock vhf dipole that came with my rtl sdr which I use as a spectrum analyzer. In one of the clips I am receiving RW7K. I have been working on the station for the past year with help from Loren Moline, WA7SKT through texts when I have a problem. The LO / VFO is from Nick Woods Videos.

Next, I will build an outdoor antenna and the transmitter section. I first started homebrewing at the beginning of the pandemic, but this is by far my largest accomplishment. I would like to thank you and Pete for the soldersmoke videos which have been a great inspiration.

I will send more updates when the transmitter section is finish along with a much longer description of the projects

Thank you

Justin Elliott
AC8LZ

Bill, Pete, and Dean 

Thank you for the compliment. Pete, I want you to know, I’m a huge fan and I enjoy the one-liner jokes. I enjoy your contributions to the videos when you’re on Dean. 

Here are pics / videos of my superhet. 

The bandpass filter is a homebrew version of qrp labs design for 40m, I had to add an extra capacitor to get the bandpass where I wanted it. It is 6.9mhz to 7.32mhz. 

Mixer / demods are ade-ask.

The rf amps are kits i bought online, assembled, then used the schematics to replicate. They are the W7OI created and which have been mentioned on the channel

The LO/VFO are arduino driven from Nick Woods (M0NTV) YouTube channel. I believe episode 26

The crystal filter was built for 9MHz, but when I swept it I found the bandpass was saw toothed, so I used a commercial filter that Loren Moline WA7SKT sent. 

The audio amplifiers are a Common Emitter Amp I found on YouTube, I can’t recall the channel and a commercial amplifier, which I can now reproduce as I have the schematics. 

The speaker is a 2W 8 ohm speaker. 

...

Justin Elliott

AC8LZ

Nate KA1MUQ's Amazing Thermatron Receiver

https://natesbasement123.blogspot.com/2024/02/thank-you-bill-dean-grayson-pete-and.html

Wow, some really wonderful work is taking place in Nate KA1MUQ's basement in California. 

-- I really like the pill bottle coil forms.  I wonder if Nate faced suspicion (and possible arrest) in the pharmacy when he asked for the pill bottles.  (I got some suspicious looks when I went I asked for empty pill bottles while building my thermatron Mate for the Mighty Midget receiver back in 1998.) 

-- The variable capacitors are also quite cool, as is the big rotary switch.   Is that for band switching? 

-- Oh  man, all on a plywood board.  Frank Jones would approve!  

-- Indeed Nate, that beautiful receiver NEEDS an analog VFO.  And we need to hear it inhaling phone sigs, not that FT8 stuff. 

-- Please keep us posted on your progress.  And of course, one hand behind your back OM.  Lots of high voltage on those thermatrons.  

Thanks Nate!  

Videos from Mike AG5VG -- His Homebrew BITX Rigs

Here are two great videos from Mike AG5VG showing his two homebrew receivers in action.  (The transmitter portions of Farhan's circuit will come later.) See yesterday's post for more details. 

On the video above (40 meters) 

-- I love that speaker.  

--  The enclosure and the reduction drive for the VFO is really great.  FB OM. 

-- Very cool that Mike captures a 40 meter QSO with "Wild Bill" ZS6CCY in South Africa, someone who we've spoken to many times, often on the long path, sometimes from Mozambique. 

-- I like how Mike demonstrates the effect of removing the antenna.  You can definitely see what we mean when we say you should be able to "hear the band noise."   

  

Above you see the 20 meter receiver in action.  You can see one of the physical benefits of using a wooden base:  You can easily mount connectors, switches and tuning controls using just pieces of copper-clad board screwed into the wood.   This is what I am doing with my latest BITX 15-10 rig. 

For the tuning of the VFO, it looks to me as if Mike has a large "main tuning" control in the center, with a smaller "fine tuning" or "bandspread" control off to the left.  Does that smaller control work with a varactor diode or with a smaller variable cap?  Also, to the right of the main tuning control we see a 3 pole switch.  Is that switch putting additional L or C into the VFO circuit to move the frequency around?  These techniques would all be quite valid;  Mike demonstrates that there are many ways to skin a cat (or tune a VFO!) 

Mike:  Please send more info. 

F6CRP's FB Homebrew Receiver

I like F6CRP's homebrew receiver.  I like the way he presents it (block by block) and I like the inclusion of the W7ZOI IF board. The JF3HZB VFO is quite cool (even though it is digital),   We have posted about this VFO several times: 

 https://soldersmoke.blogspot.com/2022/05/who-is-jf3hzb-creator-of-that-nice.html

Denis has a very nice station and workbench: https://www.qrz.com/db/F6CRP

He also has some very nice videos on his YouTube channel: 

https://www.youtube.com/@radiorider8249/featured

Thanks Denis! 

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

The Awesome Homebrew of Will KI4POV

 

Will's homebrew station is really something.  The rig (it truly qualifies for this term of praise) is amazing all by itself  (see below), but a look at Will's QRZ page reveals other ingenious inventions and techniques:  There is the clock made from panel meters.  And the method he uses for making aluminum project boxes.  He even made an N0WVA regen receiver.  That's the one I used in my ET-2.   Fantastic.  

Will really needs to share his homebrew skills with others.   I hope he is soon in a local high school teaching students how to build things.  Thanks Will!  

Bill and Pete,

Just wanted to send a note to update you on the latest projects here. The last time I emailed, I mentioned wanting to build a superhet, which you (rightfully) discouraged, pushing for a DC receiver.

Well, I finished the superhet at the end of last year. I had most of the receiver working long before then, but got bogged down in an AGC system. The final receiver is a 5 band si5351a controlled single conversion superhet loosely based on Todd, VE7BPO's design with several modifications. I used a 9 Mhz IF instead of 4, I used a digitally controlled LO and BFO, and as mentioned, I added an AGC system, which ended up being the most challenging (and most interesting) part. The final AGC system I ended up with used the detector and amplifier side of Wes Hayward's "full hang" AGC from SSDRA, but I didn't have the IC IF amplifiers with variable gain, so instead, it fed a PIN diode attenuator circuit to control the IF gain. The final result worked great, but I nearly pulled my hair out getting it to work. I originally intended to build the receiver for 40 and 20 meters, but it ended up covering 80, 40, 30, 20, and 15 since I used the filter relay board from QRP Labs which had 5 slots.

After I got the receiver running, I decided I needed a matching transmitter, so I  built up a simple CW transmitter to match. It uses an si5351a VFO driving a 74HC04 hex inverter as the buffer amplifier. The trick here is that by driving all the inverter gates in parallel, the output impedance is ~14 ohms broadband, suitable for driving a BJT PA without any need for matching transformers. The PA is 3 2N2222s in parallel with heat syncs putting out about 2 watts from 80 - 15.

The part I'm most proud of is that I have the arduino for the receiver connected to the arduino for the transmitter through a serial line. The receiver sends it's current frequency to the transmitter so that the transmitter can track the receiver's frequency as you tune (like a transceiver). I'll attach a few pictures of my homebrew station below. The transmitter is on the left, receiver is on the right. The box on top of the transmitter is my homebrew keyer. Next up on my build list is a solid state T/R switch.

Bill, I've enjoyed following the updates on the school DC receiver build. My local club is wanting to do some youth outreach, and I'd love to get them involved in building. I'm the only builder in the club though, so I don't know if I personally have the manpower to make it happen. Also, thanks for the recent info and pictures of Cuban homebrew rigs. I grew up listening to Arnie Corro, so I love seeing their resourcefulness and ingenuity. Makes me want to take apart some old electronics.

Pete, I'm enjoying following the 10M SSB project. With the uptick in propagation, I've been bitten by the 10M bug, and I'm thinking a 10M rig may have to be on my project list for this year.

73,

Will - KI4POV

KI4POV's Clock

KI4POV's N0WVA Regen

Fixing Up An Old Homebrew Rig -- Barebones Superhet and VXO 6 Watter

 

I'm not exactly sure why I pulled this old rig off the shelf, but I'll write up what I did -- I often use this blog as a kind of notebook.  I can look back and easily see what I did on my last encounter with the rig. 

The receiver is Doug DeMaw's Barebones (aka Barbados) Superhet.  This was my first superhet receiver. I built in in 1997.   The transmitter was my first real homebrew project -- it is the VXO 6 watter from QRP classics.  I built it in the Dominican Republic, probably in 1993 or 1994.  I built the power supply so that I could say that the entire rig is homebrew. 

This rig is getting a bit long in the tooth:   The receiver is built with 40673 Dual-Gate MOSFETs, an some of the transistor cans have gotten rusty.  The frequency readout on the receiver is the top of a coffee can fitted onto the reduction drive behind the tuning knob from a Drake 2-B (not MY 2B!). 

Here are two 2013 videos that I did on this receiver: 

https://soldersmoke.blogspot.com/2013/03/video-of-my-barebones-superhet.html

-- I put the crystal filter back in CW mode.  I had widened it so that I could listen to 20 meter SSB, but I decided to go back to its original configuration.  When I built the receiver in 1987, I didn't characterize the crystals -- I just used the capacitor values that Doug DeMaw had in his article.  I pretty much did that again this time, just putting caps that are close in value to what Doug had.  DeMaw used color burst crystals at 3.579 MHz.  So I guess this would be a GREAT receiver for the Color Burst Liberation Army!  

-- I used My Antuino (thanks Farhan!) to check the passband.  Here is what it looks like.  I just put the Antuino across the 10k resistors on either side of the input and output transformers.  The coil cores had become very loose -- I just tried put them in the right place.  I may need to put some wax in there to allow them to better stay in place. I think they could have used toroids instead -- that would have been easier. One of the transformer connections was open -- they don't work well that way,  once I fixed that, the passband looks like this: 

-- Each of the horizontal divisions is 500 Hz.  The passband is not pretty, but it is OK, and I  didn't feel like doing too much work on this to get it in better shape. 

-- The filter peak was a bit lower in frequency than expected.  I found that trimmer cap C3 in series with the BFO crystal would not allow me to lower its frequency sufficiently.  So I moved C3 to a position in parallel with the crystal.  With this mod, I could get the BFO frequency to 3578.69.  This produces a 690 Hz tone when the received signal is at the peak of the IF passband.  Opposite sideband rejection is quite good. 

March 2013 Rebuild of the VXO 6 watter

-- I didn't have to do any real work on the transmitter.  The RF amplifier in the transmitter had served for a time as the RF amp in by 17 meter DSB rig (I had added a bias circuit, which I removed when I put the amplifier back in Class C).  Some time ago I rebuilt the oscillator circuit (which had been literally cut off the board when I used the amplifier in the DSB rig). 

-- I did have to reconfigure the muting circuit -- the T/R switch in the transmitter switches the antenna and also -- through a two wire circuit -- cuts off 12 V DC to the transmitter when in receive mode. 

-- For sidetone I just put a small piezo buzzer through a 1k resistor between 12 V DC and the key line. 

It all worked fine -- I talked to three stations on the high end of  the 20 meter CW band. 

Phase Noise and all that

Our friend Dave K8WPE has been listening to old podcasts.  He recently came across those in which Pete and I were talking about phase noise.   He asked for some resources on this topic.  Here is what I sent him: 

 Receiver performance expert Robert Sherwood explains it this way: 

Old radios (Collins, Drake, Hammarlund, National) used a VFO or PTO and crystal oscillators to tune the bands. Any noise in the local oscillator (LO) chain was minimal. When synthesized radios came along in the 70s, the LO had noise on it. It is caused by phase jitter in the circuit, and puts significant noise sidebands on the LO. This can mix with a strong signal outside the passband of the radio and put noise on top of the weak signal you are trying to copy. This is a significant problem in some cases: You have a neighboring ham close by, during Field Day when there are multiple transmitters at the same site, and certainly in a multi-multi contest station. You would like the number to be better that 130 dBc / Hz at 10 kHz. A non-synthesized radio, such as a Drake or Collins, has so little local oscillator noise the measurements were made closer-in between 2 and 5 kHz. 

http://www.sherweng.com/documents/TermsExplainedSherwoodTableofReceiverPerformance-RevF.pdf

Rhode and Schwarz have a good oversight video with great graphs that explain the fundamentals,  See above or here:  https://www.youtube.com/watch?v=hfgaEjf1154 

I think a lot of the fretting about advanced receiver performance measurements are really kind of over-the-top, and mostly of interest to advanced builders who want the very best performance from their receivers.  Most of the rest of us are happy if we can hear the band noise and separate the desired signals from the QRM.  But I must admit that as time goes on, I find myself getting more and more finicky.  I start to worry about gain distribution and dynamic range.  But I don't worry so much about phase noise because I am more of an LC oscillator guy and don't make much use of the PLL devices (like the Si5351) that do produce more phase noise. 

I've had many articles on the blog about about phase noise.  Here they are: 

https://soldersmoke.blogspot.com/search?q=%22phase+noise%22

W1VD's Boatanchor Receiver Tests

I've been trying to get more rigorous in my evaluation of receiver performance.   My HQ-100 is tuned to Radio Marti, and it sounds great.  But how great is it really?  And what about all the receivers and transceivers I have built?  How good are they?  

Our friend Dean KK4DAS is about to start the rehabilitation of his dad's old HQ-170A.   A search for that receiver led me to Jay Rusgrove's very interesting measurement and analysis of old tube type radios.  Jay's results appear in the links below.  More important is his very clear description of how the tests were done and what the results mean (link below). Also included is one link showing a discussion of Jay's work.  

Jay notes: 

The decision of which boat anchor receiver(s) to own is seldom based on performance alone. A combination of favored manufacturer, period of manufacture, features, collectability or even just 'looks' often rank higher on the priority list than receiver performance. Even if one were interested in performance specs much of the available information is subjective as few receivers manufactured prior to the mid 70s have undergone standardized testing. Hard data on minimum discernable signal (MDS), blocking and two-tone IMD dynamic range is interesting to some operators and important in an historical context as it shows the progression of receiver development.

Jay designed the very first real transmitter that I homebrewed (The VXO 6 Watter from QRP Classics). Jay has been mentioned many times in the SolderSmoke podcast and blog:    

Jay's results:   http://www.w1vd.com/BAreceivertest.html

Jay's methods:  http://www.w1vd.com/Receivermeasurementbasics.html

Discussion: https://www.antiqueradios.com/forums/viewtopic.php?t=96872

Mr. Carlson's Grand Receiver Restoration Project -- Your Input Sought (video)

Mr. Carlson (VE7ZWZ) is launching a series of videos on the restoration of some old boatanchor receivers.  I have been working on an old HQ-100, so this all resonates well with me. 

He asked for viewer input on which of these receivers he should work on first.  I voted for the SP-600 because I wanted to see how difficult it really is to change out the infamous Black Beauty capacitors.  My second choice was the R-390, but I warned Mr. Carlson that he might need a chassis crane for that one.  No kidding.  Really.   

I look forward to watching the series.  Thanks in advance Mr. Carlson. 

Level UP EE Lab Builds a Superhet Receiver

I was really glad to have stumbled across Darren's YouTube channel: 

(46) Level UP EE Lab - YouTube

Heck, he has an S-38E on the shelf above his bench.  He is clearly one of us.  What is his callsign?  

This morning I watched the first and last of his 10 videos on his superhet receiver project.  Very cool.  Lots of good info in there.  And there is something for everyone:  Arduinos and Si5351s, along with a lot of standard analog circuitry.  The first episode appears above. 

The variable bandwidth filter looks very interesting. And there was a nice shout-out to Charlie Morris and one to Hans Summers. 

I really like his effort in episode 10 to measure Minimum Discernible Signal using commonly available test gear.  This helped me in my effort to get more rigorous and serious about receiver performance measurement.    

Darren has many other excellent projects on his YouTube channel.  My Hammarlund HQ-100 receiver started giving me trouble this week, and I was debating whether or not to fix the old thing.  Darren's channel provided the inspiration I needed.  It will be fixed!   

Please subscribe to Darren's channel.  And spread the word about his videos.  We definitely want him to make a lot more.  

Thanks Darren!