Month: March 2022

Mike WU2D Looks at the “Dream” SW Receivers of the 1960s and 70s (Video)

Wow, I really liked Mike’s walk down memory lane. I saw several of my own dream receivers:

S-38E. Indeed, this little monster did add some danger to your life. AKA “The Widow Maker,” I gave one to my cousin’s husband so he could listen to what the commies on Radio Moscow were saying. He later told me that the receiver had given him a shock. I now have TWO S-38Es in my shack (two more than I really need). I have installed isolation transformers in both of them, so they have lost the one element (danger!) that made them attractive.

HA-600A. I got this one for Christmas in 1972. The A model is MUCH better than the plain vanilla HA-600. I recently got another HA-600A and found serious deficiencies in the Product Detector. Has anyone else noticed these problems? BACKGROUND INFO AND A PLEA FOR MORE INFO HERE: https://soldersmoke.blogspot.com/search?q=HA-600A+Product+Detector

HQ-100. Got one in the Dominican Republic. Fixed it up, repairing damages caused by radio life in the tropics. Disabled the goofy audio amplifier circuitry. I now wonder if this receiver might benefit from the insertion of a 455 kc ceramic filter.

NC190. Wow “Cosmic Blue” Perhaps this was an early influence that led to “Juliano Blue?”

HQ-180. “18 tubes and almost as many knobs!” FB!

HRO-500. Love the dial.

Transoceanic. Never had one, but built a BFO for the Transoceanic that W8NSA took with him to SE Asia during the war.

R-390A. I don’t have a crane for the workbench.

Thanks Mike — that was a lot of fun.

Vienna Wireless Winterfest Hamfest 2022

After a two-year pandemic hiatus, yesterday the Vienna (Virginia) Wireless Society’s annual “Winterfest” hamfest was back. And the weather was in fact COLD — it definitely felt like Winterfests of years-gone-by.

Club President Dean KK4DAS kindly invited me to participate in a forum on homebrewing. You can watch the presentation STARTING AT 2:04:06 (hours:minute:seconds) here:

https://www.youtube.com/watch?v=s48of3uS9tM

It was especially cool to be able to tell the audience about Pete N6QW and Farhan VU2ESE. We talked about Pete’s Simple SSB transceiver, the Michigan Mighty Mite and the BITX rigs.

Some observations on the hamfest scene:

— There are lots of boatanchor radios out there, and it seems like a buyer’s market. These old rigs do not seem to be selling nearly as fast as they did a few years ago.

— There is a lot of older analog test gear on sale too, and it too seems to no longer be as in demand as it was a few years ago. Perhaps the availability of cheap, small, and very effective digital oscilloscopes is affecting the sale of these once sought-after items.

My purchases:

— A really old beat-up (crashed?) ARC-5 R-23 receiver. I have already extracted the variable capacitor.
— A nice box of smaller variable caps.
— 100 feet of 550 parachute cord.
— Two nice metal chassis/boxes
— A bag of shaft adapters/connectors

With Armand WA1UQO (left) and Steve Boles W4SB (center)

With Charles AI4OT


Thanks to Dean KK4DAS and the entire VWS team for a great event.

Getting More Rigorous About Receiver Design (Video)

As I finished up the receiver on my 17-12 SSB transceiver, I started to wonder — how good is it?
Sure, I could hear stations on both bands, and when I got started as a homebrewer that was enough for me. But now, I find myself wondering about receiver performance. Did I get the gain distribution right? Do I have too much gain ahead of the mixer? Ahead of the crystal filter? Is the receiver generating too much noise? Can I hear the band noise? If not, why not? Do my circuits lose linearity in the presence of strong signals? What is my dynamic range?

This is a big complicated subject that takes time to master.

I am just beginning. I found the video above to be very helpful.

I was jealous of this fellow’s audio spectrum analyzer, but then Tony G4WIF told me that the the analyzer that this fellow was using was really just a sound card and some software. I quickly found a similar piece of free software that lets me do the same thing he did: Look at the audio output of my receiver and watch what happens as I put an RF signal of varying levels into the antenna port.

I am using Visual Analyzer, a free program out of Italy:

https://www.sillanumsoft.org/

The author of the software seems very cool”

My name is Alfredo Accattatis; I love electronics and software, and I have been working for years in commercial companies as software/firmware engineer and software designer. I’ve been writing programs for embedded systems (with DSP and MICROCONTROLLERS), for PC, for Avionic Computers and even for Mainframes, using C, C++, Pascal, Ada, REXX and assembly. I starting write VA during my free time just for fun and using (also) my DSP experience. The program was and is completely FREE.

More info about Alfredo here:

https://www.sillanumsoft.org/about_the_author.htm

Do you folks think I need to buy the kind of True RMS Audio Voltmeter that is being used at the end of the above video?

First Ever Contact on 12 Meters: Homebrew, QRP, SSB, DX (Video)

I’ve recently finished most of the circuitry on the 17-12 meter dual band SSB transceiver. I have had contacts with it on 17 meters, but until yesterday morning (March 22, 2022) I had not had any contacts on 12 meters. This morning I talked to Paul EA5JZ in Valencia, Spain. I was running the 17-12 rig barefoot at about 5 watts with the final being one RD06HHT FET. The antenna was my 75 meter doublet fed with window line — I had to modify the tuner to get it to work on 24.9 MHz. It was very cool to have my first 12 meter contact be QRP, HB and with Spain.

There is a LOT of soul in this new rig. Here is a partial list of contributors:

— Overall BITX design: Farhan VU2ESE

— Termination Insensitive Amplifiers (TIA): Wes Hayward W7ZOI and Bob Kopski K3NHI.

— TIA boards from Todd K7TFC

— ASK-1 Mixer from Armand WA1UQO

— VFO design parameters from Joe Carr K4IPV (SK)

— VFO stability ideas from Frank Harris K0IYE and Mike Murphy WU2D.

— HT-37 Tuning Capacitor bought from e-bay at suggestion of Pete Juliano N6QW.

— Pine board base of the rig: Frank Jones (SK) W6AJF’s preferred building technique.

— DTC Band-Pass filter circuits from Han Summers G0UPL.

— Low pass filter values from G-QRP web site.

— Idea of using RD06HHT instead of IRF-510 in the final: Pete Juliano

— Heat sink from Chris KD4PBJ

— Trifilar Toroids used in many places from Farhan VU2ESE.

Thanks to all. 73 Bill

Receiver Dynamics — How Good is my Receiver?

OK , so I’ve finished building my new 17-12 Dual Band SSB Transceiver. I am now testing it out on both bands. A big question I have is this: how good is my receiver? Did I get the gain distribution right? Is it generating too much noise? Are any of the stages too vulnerable to distortion in the presence of large signals?

These kinds of questions are at the heart of receiver design. Many of us have for years just thrown together amplifiers oscillators and mixers, and have been pleased if we could copy signals on the ham bands. But could we have been doing it better?

This is a very complicated issue, and unfortunately much of the literature is plagued by jargon and unnecessary complexity. Rarely do we find something that goes from the general to the specific and explains what it is we are trying to achieve: We want the receiver to be sensitive, but we don’t want it to be so sensitive that it distorts with strong signals. It will make some noise, but we don’t want the receiver’s internal noise to be stronger than the noise coming in from the antenna. The “front end” stages are very important because any flaws there will be amplified by the follow-on stages and will “cascade” down through the receiver. Bandwidth is very important.

This morning I found (again!) a document that defines terms in a very clear way. Be sure to check out the footnotes mentioning Dave Newkirk and Wes Hayward! FB! Here it is:

https://www.nsa.gov/portals/75/documents/news-features/declassified-documents/cryptologic-quarterly/Receiver_Dynamics.pdf

17 – 12 Dual Band SSB Transceiver On-The-Air

It is still completely al-fresco, with all the guts exposed, but I got it on the air this morning. I was 17, running it through my CCI .1kW 100 watt amp to a tuned doublet. Four QSOs so far: HP3SAM, K5BM, N4ZUL, and II3WRTC.

The structure of the rig is basically BITX.

The blue boards you see are TIA boards developed by Todd K7TFC.

No major problems to report. I will try it out on 12 meters soon. The receiver was working well on that band.

Flick Lives — More from a Great Web Site about “Jean Shepherd”

Jim Clavin has some really great stuff on his FlickLives website:

Much of this stuff I had never seen. Like the picture he has of young Shep in his shack. I wonder how old he was in this picture. He appears perturbed. Perhaps his Heising Modulator was distorting?

Jim dug up all of Shep’s licenses and got the names and callsigns of all the hams who were active from Shepherd’s hometown during the years Shep was living there. I think I can recognized some of the names — Shep talked about some of these guys when talking (on WOR) about ham radio. Boles. Stan. Good times.

The CQ Guest editorials and the various articles are a lot of fun. Some things never seem to change.
Thanks Jim!

EXCELSIOR!

Help! Can You Write the Software to Control the MAX2870 Board?

It is not every day that you get the chance to help a master homebrewer like Pete Juliano N6QW. But today is just such a day. Pete asks for some coding help:


The Radio Gods would be pleased if you help. The Mojo and Juju levels of all your projects would increase. If you can help, please do so.

Colin M1BUU’s Homebrew Manhattan SST

Wow, especially on St. Patrick’s day I think it is appropriate to say ” ’tis a thing of beauty. “

Colin did a great job on his homebrew version of the SST transceiver. It looks like his is on 30 meters. I especially liked his description of the troubleshooting that followed the construction. the assist provided by AA7EE’s blog was especially cool, and demonstrates the long-lasting power of internet-shared tribal knowledge.

Colin wrote (on Facebook):

I was inspired by Bill and his adventure with the SST-20, so I started gathering a few parts last year to build a Manhattan SST. I did a joint SOTA activation with a fellow homebrewer ham at the end of January and we started talking about classic portable CW rigs, it turned out that we both had an SST build on our ‘list’. I was challenged to build the SST for the next joint SOTA activation!
It took a lot of effort and a few late nights but I did manage to produce a rig capable of making QSOs for a joint SOTA activation of Fair Snape Fell, G/SP-007. I’d done a solo activation of Pendle Hill G/SP-005 a few days before with the rig for a trial run and I discovered that the AF was very low. After some troubleshooting I noticed that I’d soldered the LM386 gain set capacitor to an incorrect pad. Doh! I fixed my error and the rig had much more gain.
I found that with the improved AF gain, the rig would squeal if the gain was turned up. I was ready to give up really, but after a cool off period, I began researching the issue and it turns out that it’s very common and indeed I found posts from 1997 about it! It seems as though my recreation was so faithful to the original, I’d included the original flaws too! I added in a 0.1uF cap and resistor connected to pin 5 of the AF amp chip as per the suggestion on Dave AA7EE’s blog and now the squealing has stopped.
I’d made 14 QSOs during the joint SOTA activation, so I considered my challenge to have been met! It’s been a bit of an epic build!
73, Colin, M1BUU

Pete N6QW Looks at Tapped Capacitance Impedance Matching

For some reason we are more accustomed to impedance matching using tapped coils than we are with the use of tapped capacitors. This is too bad because tapped capacitors are a very useful impedance matching tool. Pete recently looked at this technique. Check it out:

VK2BLQ’s Two-Tube Regen with a SolderSmoke Dial

Thanks to Peter Marks VK3TPM (“a bloke with too many hobbies”) for alerting us to this magnificent homebrew receiver with the especially magnificent tuning dial.

We have used old CDs as dials for many years. I have one on my Q-31 Quarantine SW receiver. But never have we seen one with SolderSmoke emblazoned on it. FB OM.

Stephen VK2BLQ should make sure that those 6U8s haven’t gone old on him. I recently replaced the 6U8s in my Mate for the Mighty Midget with 6EA8s. This seemed to rejuvenate the receiver.

Also, it is shame that Stephen doesn’t keep that rig at 12 volts. 250 V? Yikes. As I often say, you CAN hurt yourself with 12 volts, but you really have to work at it. Not so with 250 V. One hand behind your back Stephen!

Thanks to Peter and Stephen.

Video #3 17/12 Transceiver — Receiver is Working on 12 and 17 meters (Listen! Video!)

Here is an update on the 1712 transceiver project. The receiver circuitry is done and I can listen on 17 and 12 meters. In this video I was using my 75 meter doublet tuned to 17 meters (reception on 12 was pretty good using this antenna). As you can see, I found a temporary solution to the VFO dial problem — I am using the cardboard tube from a coat hanger super glued to a knob. The tube fits snuggly over the shaft from the VFO assembly.

Hans Summers’ QRP Labs Bandpass Filters:



Thanks Hans!

Video #2 17/12 SSB Transceiver — Receive RF Amplifier Needed?

Lots of progress to report on the 1712 rig.

With just two TIA amps (one on either side of the 10 pole filter) and the AF amplifiers, I now have it inhaling on 17 meters. But nothing heard so-far on 12. On both bands I can hear the band noise, but just barely. So I may try some RF amplification ahead of the mixer. What do you guys think about this? I think the two TIAs and the crystal filter are providing 30 db of gain.

I want to get the receiver circuitry working well on both bands before I build the T/R and transmit amplifier circuitry.
It is nice to have a project on the bench!

I am trying to find a shaft extender or adapter for that big beautiful HT-37 main tuning cap. The shaft on the capacitor has a width of 1 cm or 0.393701 inches. I need something that will grab onto that and allow for the connection of a tuning knob. Please search your junk boxes!

Dennis WC8C’s FB Homebrew 6 Meter Rig — Any Ideas or Suggestions?

Dennis WC8C is the event coordinator for the radio club in Michigan that I recently spoke with. He mentioned to me that he was working on a homebrew 6 meter rig. FB Dennis. I see lots of tribal wisdom in your approach, especially in your decision to do this in a stage-by-stage modular form.
Dennis’s rig is obviously a work in progress, so if anyone out there has any helpful hints (especially on the carrier suppression and on the testing for spurs and splatter) please share them with him via e-mail or blog post.

The files on Dennis’s rig are on GITHUB: https://github.com/soligen2010/6_Meter_Transceiver

Thanks Dennis!
—————-

This is my 6 Meter homebrew transceiver, currently work in progress. It is a single conversion super –heterodyne design. I constructed each stage independently with SMA connectors. This is so I can re-make sections as needed, and will allow me in the future to swap sections to experiment with alternate designs. The VFO and BFO are controlled using a SI5351 with an Arduino micro controller. I currently have separate SI5351 modules for VFO and BFO because I suspected issues with cross-talk. These issues may not actually be real, so once I am happy with the performance, I will test again with just one module to see if it is OK. The Power Amp is still on the to-do list, so output is well under 0 DBm

The Blue boards were designed by me and ordered on-line. The other boards I etched myself. Construction is mostly surface mount because I find it easier than drilling all the holes. SMD components are mostly 805 and 1206 size. Transistors are SOT23.

The Band Pass filter is a 5 coil design made with air-core inductors.

3 bi-directional termination insensitive (TIA) amps are used (blue boards). Total RX gain is about 44db. Total TX gain is about 16db. Each board has its own independent RX/TX switching circuitry (mosfet based) and is fed with +12.5, GND, and RX/TX logic signal from the Arduino (3V logic and up will work)

The Mixer and modulator are both Diode Ring mixers.

The 12 MHz SSB filter is a crystal ladder filter similar to the one used in the uBitx.

The Mic and audio pre-amp (also a blue board) is made on a modified TIA amp board. I had 10 of these boards made, and the needed circuitry was largely the same, so I modified the board with a rotary tool and jumpers.

The Audio amp is a PAM8403 module and drives a headset. I did make some modifications to the module so it runs in-spec and to eliminate the power on audio pop.

The challenges I have been having are mostly related to spurs, splatter, carrier suppression and TX audio quality. I have been gradually tweaking these things to improve operation before I start on a power amp. My IF is 12 MHZ, and I was using the LSB side of the crystal filter because it is sharper (VFO 62 – 66 MHz) but have recently changed over to the USB side of the filter (VFO 38 – 42 MHz). This eliminated the spurs I was seeing near the pass band. I still need to make some adjustments to the crystal filter as it is too broad.

I still have some splatter and audio quality seems low, but I am starting to doubt my test setup. I see the splatter on the RTL SDR, but I don’t see it on the Tiny SA. The spatter happens at ~160 KHz intervals. I am hoping to find someone local with a better spectrum analyzer to help me verify if it is the rig or my SDR dongle/test setup.

The modules to the side of the picture are my rejects/experiments. The one covered in copper shows how I eventually will shield all the modules. I 3D printed a cover for the board, when wrapped it with copper tape, soldered to the bottom ground plane. The one shown is a diode ring modulator. For some unknown reason the carrier suppression is rather poor. I had previously made a junk-box modulator that had much better carrier suppression. I don’t know why it is better than the one I more carefully made for the radio, but until I figure it out, I am using the junk box version. The junk box modulator uses unmatched schottkey diodes, whereas the “final” one uses a 4 diode SMD package because I wanted them matched – I thought this would be better, but maybe not.