Who is this person? He is in a prominent position in Artie Moore's very early radio shack. Artie was obviously big on labeling things, and there is a label under the picture but I can't make it out. What do you folks think? Who is this?
Friday, April 28, 2023
High-School Students Successfully Avoid THE SHELF OF SHAME -- Update on the Direct Conversion Receiver Project
One of the first finished receivers
Dean KK4DAS, Mike KD4MM, and I had a good day at the local high school yesterday, even after a month of spring break and other absences. We thought this might have been our last session at the school this year, so we strongly encouraged the students to GET THE RECEIVERS DONE. We told them about the Shelf of Shame, and warned them not to half-way finish something that would gather dust at the bottom their parents' closet. They were close to success! It was time to finish the project.
We warned them not to be perturbed if the receiver doesn't work the first time they power it up. This is not "plug and play." The receiver would likely need some trouble shooting, or at least some peaking and tweaking. We noted that we often have to sort of coax a signal out of a newly built receiver.
We soon had the students come forward with two projects that were ready for final testing. Sure enough we found problems with both. The solutions provided a lot of educational fun.
The first group had not yet built the diplexer -- we advised them to skip over the diplexer for the moment -- just connect the output of the mixer to the input of the AF amplifier. We can't let the perfect be the enemy of the good! Build the diplexer later, but for now, get the receiver going. They did, and a few minutes later they were receiving signals from Mike KD4MM's transmitter (on the other side of the lab).
Then a second group came forward. We put a San Jian frequency counter on the PTO output. Uh oh. Trouble. Gibberish! A wonderful troubleshooting session ensued. With the student, we found that the signal was good at the output of the oscillator transistor, but NOT at the output of the buffer. At first we suspected that the buffer was bad, but it was not. Then we lifted the connection to the mixer and suddenly the buffer output was good. So the problem was in the mixer! When we disconnected the input transformer of the mixer from the diode ring, THE PROBLEM WAS STILL THERE. So the problem was clearly in the input transformer. Dean gave us a replacement transformer. Soon all was right with the rig, and this group joined the ranks of the successfully completed receivers.
I think that seeing that two groups had finished helped motivate the others. Our announcement that successful completion would lead to a "Certificate of Completion" also helped. But most of all, I think the natural desire to finish the job and avoid the "Shelf of Shame" was pushing the students forward.
Other news:
-- Our stage-by-stage award program continued. Last time we awarded "The Torry" for the first successful bandpass filter; this time we awarded "The Audy" for the first successful audio transformers.
The Audies
-- We told the students that their work has been entered in a Hack-A-Day contest. Most of the info and files on the project can be found on the Hack-A-Day site. Check it out:
https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver
-- We also told the students about Walter KA4KXX's very generous offer of a reward for the first students to check into the Florida Sunrise net. (We had to make it clear that this offer is completely extracurricular and unconnected in any way from the school .) The students were clearly intrigued. Sunrise Net may get some new check-ins!
-- We provided instructions on how to build a simple 1/4 wave reception antenna. We also did a video.
We had thought that this would be our last session at the school, but at the students' request we will be back with them next week for another session. We think there are at least five more receivers approaching the finish line.
Wednesday, April 26, 2023
Retro QRP Rigs of the 1960's, 70's, and 80's -- Video by Mike WU2D
It is time to put aside (again!) all of the heated ideological arguments about the power level that defines "low power." Just sit back and enjoy this wonderful trip down QRP memory lane.
Mike's description of the simple, single-transistor QRP transmitter was really nice. I recently made something similar: https://soldersmoke.blogspot.com/2023/02/first-qso-with-high-school-receiver-100.html And Mike does a nice plug for our beloved Michigan Mighty Mite. Go CBLA!
The modular idea: words to live by my friends.
40673! TT2! And G3RJV's PW Severn - indeed, bow your heads!
Wow, the Ten Tec Power Mite (or Might!) -- I still want one. Same for the Argonaut -- what a great name (sounds like a "magic carpet), and with SSB to boot! I want to join the Argonaut cult!
I have both the HW-7 and HW-8 (the HW-8 is heading to the Dominican Republic). This video makes me want to fire up the HW-7. Maybe on 40.
My 40 meter homebrew rig (Digi-Tia) has in it the filter from that old Yaesu FT-7 rig. The filter was given to me by Steve "Snort Rosin" Smith. https://soldersmoke.blogspot.com/2015/05/bitx-digi-tia-build-update-2-installing.html
Thanks to Mike for including me in the credit roll at the end. What a great group of people -- it is a real honor to be listed with those folks.
Monday, April 24, 2023
Tim Hunkin on Drilling Holes (Secret Life of Components Video)
I guess that aside from being a great video, this is something of a test of technical nerdy-ism. If you find this hour long video really interesting, well, you know...
Really cool stuff from Tim Hunkin:
-- I liked the angle driller. Need one.
-- The placement of the magnets near the hole to catch the shavings was really cool.
-- Tim's reluctant admission that it is just better to buy new drill bits (as opposed to sharpening old ones) is good advice.
-- WD-40! Yea!
-- Note: No white "Boffin" coat for Tim. Just "overalls." But as I watched I found myself thinking that he could probably have used an armor plate or at least a Kevlar vest amidst all that flying metal. Perhaps a bit more eye protection too...
-- Fiddley. A useful tech term.
--Swarf: Another useful tech term: the metallic remnants (shavings) of drilling.
-- The digi readout on the milling machine looked really useful.
Finally, I loved the sign that Tim has posted in his workshop:
SMALL HADRON COLLIDER
Four Old BBC Shows on Radio: Hams, Physics, and Antique Wireless
The first one, about ham operators in general, is pretty depressing. Then it goes downhill as they shift to those who are listening to baby monitors and cell phones. Yuck.
The second one seems to show some physicist having understandable difficulty explaining particle-wave duality in a short TV segment.
There is a short bit (that I didn't quite get) about the BBC's "Teddy Bear's Picnic."
The final one is about Gerald Wells and his Antique Wireless Museum in South London. Note the white coat -- clearly a boffin. For a while I confused him with Rupert Goodwins G6HVY (similar white coat, but a different bloke).
Sunday, April 23, 2023
Helge LA6NCA's Altoids Tin Receiver
Here's another great video from Helge LA6NCA. This is a follow-up to his Altoids Spy Transmitter project. Really well done. Hack-A-Day called this receiver "regenerative" so naturally I was disappointed, but when I watched I realized that it is NOT a regen but is instead a direct conversion receiver. TRGHS. All is right with the world. Thanks Helge! 73
Thursday, April 20, 2023
Artie Moore and the Titanic
I had never heard of Artie Moore, but his is a very interesting story from the earliest days of radio.
https://www.facebook.com/groups/118053768802799
Tuesday, April 18, 2023
A Request for Digital Help from a Ham in Argentina
Can someone out there help OM Martin LW9DTR?
His e-mail is on his QRZ.com page: https://www.qrz.com/db/LW9DTR
MARTIN LW9DTR has left a new comment on your post " The JF3HZB Digital VFO Dial in the DJ7OO Direct Conversion Receiver (Who is JF3HZB?) ":
Technical supportDear Klaus Kirschelmann
My name is Martin and my call sign is LW9DTR
I am writing to you from my hometown of Buenos Aires, Argentina.
I need your tech support because I'm trying to run the assembly you posted with the AD9850 + Arduino Mini + Oled to apply it in a QRP transceiver project and I've encountered two problems.
The first problem is that I can't find the code to program the Arduino on your website.
The second issue is that the QRP transceiver design I'm using requires an inverted DDS output, ie as the frequency on the display increases, the output frequency should decrease.
I lack programming skills, so I'm coming to you knowing you can guide me on what commands I can change in the program to make this happen.
I will be very grateful to you in advance for your tremendous support.
I say goodbye with all due respect and wish that this April 18th, International Amateur Radio Day, surprises you with joy and new projects.
A big and warm hug.
With respect:
Martin Silva, LW9DTR
CuriousMarc Powers up (and Explains) Old Cathode Ray Tubes
Wow, really cool video from CuriousMarc and the guy who wrote the "Open Circuits" book. But fellows, you really need to be more careful with the high voltage. Remember poor Ross Hull. One hand behind the back would help. Volts jolt, but mills kill.
Sunday, April 16, 2023
Inside "Open Circuits"
Here is a cool video about a very cool book. I wasn't going to buy it, but when I saw it in a book store, I opened it up to a random page and found myself looking at the 2N3904. TRGHS. So I bought it.
Thursday, April 13, 2023
The Franklin Oscillator: A Super-Stable VFO. Why No Attention? Why So Little Use?
My Franklin VFO
Lee KD4RE of the Vienna Wireless Society has been talking about the Franklin oscillator. He has been telling us that it is very stable, and capable of stable operation up through the ten meter band. Lee wants to build an direct conversion receiver for all of the HF bands with one of these circuits.
I was skeptical. First, I'd never heard of this circuit. I'd grown up in ham radio on a steady diet of Hartley and Colpitts and Pierce. Vackar or Clapp were about as exotic as I got. And second, I'd come to accept that it is just not possible to build a good, stable, simple, analog VFO for frequencies above around 10 MHz. For example, in his Design Notebook, Doug DeMaw wrote, "VFOs that operate on fundamental frequencies above, say, 10 MHz are generally impractical for use in communications circuits that have receivers with narrow filters." DeMaw was known for resorting to variable crystal oscillators.
But then this month Mike Murphy WU2D put out two videos about his use of the Franklin oscillator circuit in a direct conversion receiver at 21 MHz. The VFO was shockingly stable. I began to believe Lee. I fired up my soldering iron and built one.
WU2D's Franklin Oscillator
Lee was right, it is in fact remarkably stable, even at higher frequencies. My build (see picture above) was a bit slap-dash and could be improved a bit, but even in these circumstances here is what I got. This was with a stable 6 Volt Supply and with only a cardboard box covering the circuit:
Local time Frequency
0543 19.1114 MHz (cold start)
0636 19.1116
0804 19.1117
1034 19.1118
1144 19.1117
I started digging around for references to the Franklin. There was nothing about it in Solid State Design for the Radio Amateur, nor in Experimental Methods of RF Design. Pat Hawker G3VA (SK) did discuss it in his Technical Topics column in RADCOM, February 1990. Pat gave a great bio on Charles S. Franklin (born in 1879 and a colleague of Guillermo Marconi). But tellingly, Pat writes that, "Despite its many advantages, the Franklin oscillator remains virtually unknown to the bulk of American amateurs."
QST "How's DX" August 1947
It wasn't always unknown. In the 1940s, we see articles about the Franklin oscillator circuit. There is a good one in the January 1940 issue of "Radio." The author W6CEM notes that the circuit "is probably familiar to only a few amateurs." It shows up in the "How's DX" column (above). And the 1958/1959 issue of Don Stoner's New Sideband Handbook we see a lengthy description of the Franklin oscillator. Stoner wrote: "The author's favorite oscillator is the 'old time' Franklin, and it is believed to be the most stable of them all! This rock-solid device can put a quartz crystal to shame! Because it represents the ultimate in stability, it is the ideal VFO for sideband applications." And we see a PTO-tuned Franklin oscillator in the July 1964 QST. And it is in the fifth edition of the RSGB Handbook (1976).
Here is the January 1940 "Radio" with the Franklin oscillator article on page 41 by W6CEM:
Here is the July 1964 QST article:
There was an article about the Franklin oscillator in 73 magazine by W4LJC in February 1999:
The author notes that:
Much more recently (2022), Mike WN2A, modified his Mousefet transmitters (seen in QRP Classics in 1992) to include the use of the Franklin VFO circuit. Mike's documentation is really excellent. Kostas SV3ORA has a Franklin oscillator in his Super VFO circuit. Hans G0UPL has one on his site.
Look, there may be reasons why the Franklin oscillator has been ignored. But the circuit sure seems to present a lot of advantages. Stable operation beyond the 10 MHz barrier is the big one. Simplicity is another. If there are problems and shortcomings, let's hear about them. But it seems as if the Franklin oscillator may provide the opportunity for us to build stable VFOs beyond 10 MHz without resort to complicated PLL stabilization techniques, and without opting to go with an Si5351 or other complex digital devices.
So let me ask: Why hasn't the Franklin oscillator been given more attention, and why haven't we seen more use of this circuit by hams or even by manufacturers?
Wednesday, April 12, 2023
Farhan's sBITX -- Taking Orders! (Video)
It is really looking great. Congratulations to Farhan for bringing yet another amazing rig to the amateur radio community.
Order yours here:
https://www.hfsignals.com/
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