Month: December 2018

HT-37 Choke Failure — Why did this happen? What is your diagnosis?

Look, it has been 60 years, so I’m not looking for my money back or anything, but having just repaired the LV power supply choke on my very venerable Hallicrafters HT-37, I started thinking about how and why it failed.

Clues:

— I found it with four of the windings broken, with the eight broken leads kind of sticking out of the winding wrap.

— The four broken leads were on the outside of the winding (thank God!) an were at the part of the winding closest to the chassis and the back of the cabinet. (See picture below.)

— There was evidence of burning on at least two of the leads.

— The choke is located in the extreme back corner of the chassis, near the back of the cabinet.

— The paper and cellophane wrapping around the windings was a bit deteriorated.

So, what is your diagnosis? What happened to cause the choke to go open?

KC1FSZ’s Peppermint III Homebrew BITX with Mods


Hi Guys:

I had some time over the holiday to finish off my second scratch-built rig. I am very thankful that I got the work done on these projects before I read Pete’s “Don’t Build It” diatribe. That would have been very demoralizing. 🙂

Scratch build #2 (called Peppermint III) is still fundamentally BITX although I’ve made changes this time around. I’ve switched to ADE-1 mixers with LO ports driven by adjustable gain buffers (ala N6QW LBS). I’ve noticed that performance can be improved a lot if you can buffer/tweak the LO levels of the VFO and BFO (particularly carrier suppression on TX). I did W7ZOI TIAs in the IF chain. I’ve also taken the shielding/layout of the finals more seriously and have been able to dial up the power a lot (I did the KB1GMX thing with cutting off the drain pin on the IRF510 and using the tab). The software is also greatly improved and now supports LSB/USB modes as well as software-driven PTT control for RTTY/FT8 and the hooks for my poor man’s panadaptor. I’ve been working lots of stations on QRO.

Total build time was about three months (half the time of #1) and the layout came out much smaller than before. I made a trip over to Williams/Sonoma after Christmas and picked up the 2018 edition of the Peppermint Bark candy tin on discount and I think I can make it all fit. More to follow …

Happy New Year and 73s,


 Bruce KC1FSZ


HT-37 FIXED — Thanks for all the support

Don’t worry– I covered it with tape

This week I found myself with some unexpected free-time, courtesy of the government shutdown. And of course, my thoughts turned to the HT-37. I started thinking about the open choke in the power supply. Four wires were sticking out of one side, four sticking out of the other. Figuring out which went to which would have driven me nuts. But it occurred to me that I could just wrap the four one on both sides together, and then just connect them with a piece of wire (see above). I’d end up sacrificing three windings, but that shouldn’t matter.


It worked. My AADE L/C meter won’t measure up into the full Henry range, but the choke was no longer open and the resistance looked right (about 230 ohms).

I put it into the HT-37. It works. I had a long rag chew with AE2EE — a guy who really knows his boatanchors. He said it sounded great. This contact was like icing on the cake. TRGHS.

Thanks to everyone who wrote in with offers of parts or suggestions on how to acquire a suitable replacement.

Special thanks to Steve Murphy, N8NM who removed the LV choke from a junker HT-37and mailed it to me JUST AS I WAS LEARNING THAT THIS REPAIR WOULD WORK. I feel bad about putting Steve to the trouble. I blame the shut-down. Idle hands are the devil’s workshop. And that broken HT-37 was bothering me.

This was a very satisfying repair. It was great fun to put the old rig back on the air. And I did it without injuring myself. Straight Key Night is right around the corner.

Terminal strip for newer caps. Repaired choke went to the two ends of the strip.


W7RLF Homebrews a Receiver — FB!



Ryan W7RLF has joined the small and elite group of radio amateurs who have homebrewed a receiver. And it is a receiver filled with soul, juju and mojo; the project was inspired by Wes Hayward and Farhan, and used components from Hans Summers. Congratulations Ryan and thanks for all the work you did in documenting your experience.

Who will be the next intrepid ham to join the homebrew receiver club?

Hello Sirs!


This month I read Wes Hayward’s post on the history and heritage of DC receivers in ham radio and it brought a lingering interest to a head. I had to build one. I run the BITX40 and uBITX group on Facebook, and I posted to the other hams there: Which DC receiver should I build? Farhan recommended his DC40. Mind you, I’ve never homebrewed a radio before, so this is all new territory for me.

I did build it, and it does work. It also uses QRP Labs stuff from our friend Hans Summers. This thing has a lot of QRP heritage 🙂 I documented it every step of the way including all of my dumb moves and things I got wrong, and my desire is to inspire others to try homebrewing the way Wes, Farhan, Hans, and you YOU GUYS have inspired me to try it. I am hooked, of course! Here’s a link to my blog to Part 1:


It’s a four part series (unofficially 5 really) with 8000 words to it, and I hope you guys enjoy it and I’d be ticked pink if was worthy of mention on your show. Here’s a video of it too:


73 to you both and I wish you the best!

Ryan Flowers W7RLF

Ghost Ship: Oscar 11 Tumbles Through Space

First — Happy Boxing Day to all our UK and Commonwealth friends.

Oscar 11 is a UK-built amateur satellite launched in 1984. It has been dead (well, almost dead) for many years. But when the sun shines on the solar panels, it wakes up and transmits. I’ve been able to hear it and — more usefully — see it on my RTL-SDR HD-SDR receive system. My antenna is my re-born (from the Dominican Republic) three element homebrew 2 meter cubical quad (see pictures below).

I’m sorry the video is a bit out of focus, but you can clearly see the trace of the signal from the satellite. Realize that my HD-SDR software is about 10 kHz off calibration. You can see the Doppler shift, and you can see the signal fading in and out as the old satellite tumbles through space. Any ideas on what the other signals seen off to the side are? Is anyone else listening for Oscar 11?

https://amsat-uk.org/satellites/telemetry/uosat-2-oscar-11/

https://en.wikipedia.org/wiki/UoSAT-2

http://www.dk3wn.info/p/?cat=47
UOSAT_OSCAR-11

All I want for Christmas is… an HT-37 L25 Choke– 9 Henries at 135 ma


 Following my own advice to prepare for Straight Key Night, I tried to fire up my venerable Hallicrafters HT-37 transmitter. It didn’t work. I quickly determined that none of the oscillators were working, so my troubleshooting focused on the power supply. Sure enough, the choke in the low voltage power supply is open. That’s bad.

I briefly considered giving up on this old rig. I don’t really like working with tubes anymore. And this thing is very heavy — a real beast. DX-100-like in its heaviness. It can be hazardous to your health just moving this thing around. Opening up the case is not easy. And there are nasty voltages in there….

But I have had this transmitter since 1973 or 1974. I have fixed it many times, in several countries. I got it from a member of the Crystal Radio Club when I was a kid. There are parts given to me by Pericles, HI8P in the Dominican Republic. I used it to transmit through Russian satellites. That transmitter is like an old friend. I just can’t give up on it.

So I need to replace or repair the choke. Is there anyone out there who has a junker out in the garage or some other source of L25? Or does anyone know of a business that could rewind the choke. Please let me know. I have decided to leave the rig on the bench until I get this thing fixed (it is too heavy to move multiple times!)

It it Hallicrafters Part Number 056-300259. L25 — 9 Henries at 135 ma. Help!

SolderSmoke Podcast #208

SolderSmoke Podcast #208 is available:

http://soldersmoke.com/soldersmoke208.mp3

 15 December 2018

 Pete and the California fires
Bill goes to Brooklyn
2 meter simplex
A return of the trivial electric motor
Audio from Mars
HF Conditions — a real mixed bag

 Pete looks back at 2018 — The Year of the SSB Transceiver — Lessons Learned

 Hans Summers, the QSX and the virtues of SDR
W7ZOI’s DC Receiver Retrospective
The 1972 Solar Flare and the Vietnam War

 SHAMELESS COMMERCE: Buy your gifts through the Amazon link to the upper right.
Consider SolderSmoke the book as a gift. Visit Pasta Pete’s for cooking ideas.

Don’t Build It! Sage — but unexpected — advice from Pete.

Straight Key Night approaches.

Book Reviews:
–“What is Real?” (Quantum Physics)
— RHdb by K6LHA.

 Movies
“Bohemian Rhapsody”
“First Man” (Not yet!)

 MAILBAG:
Steve G0FUW
Ed KC8SBV




Launch Day! Godspeed Exseed! 1:31 pm Eastern time. Video links here.

Farhan posted this message and the above video to Facebook today (I have the video cued up to around the 5 minute point):

We are all set for the launch of ExseedSat… There are two tiny switches at the bottom of the satellite that keep the satellite switched off while it stays in it’s container. Once the satellite is ejected, the switches are released and the satellite wakes up.
There are 36 satellites on this launch, some belong to close friends in the satellite fraternity. We wait for all the satellites to drift out and after 45 minutes, the antennas are depolyed and we will start beeping signals home.
Here is a test of that process. You can skip to the fifth minute to watch the antenna depoly .

 I really like the tape measure antenna. This recalls the earliest OSCAR satellites. And let’s not forget that OSCAR 1 also launched from Vandenberg. So there a lot of good tradition flying with Farhan’s bird.

Press reports indicate a launch time of 1:31 pm Eastern time today. I think you can watch it live through the video window below. Or try this link:

https://www.youtube.com/watch?v=Wq8kS6UoOrQ

Cubesat Launch Now Scheduled for Sunday Morning (California time)


Here is an update from the San Luis Obispo News:
https://www.sanluisobispo.com/news/local/article222438135.html
It kind of makes you wish you were out there…


https://spacenews.com/dedicated-rideshare-falcon-9-launch-raises-satellite-tracking-concerns/

https://www.theverge.com/2018/12/1/18114894/spacex-falcon-9-reusability-sso-a-mission-rideshare-satellites