One-tube regenerative radio spans the Pacific Ocean

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One-tube regenerative radio spans the Pacific Ocean

Post by dan88king on Fri Oct 18, 2013 11:44 am

About ten years ago I happened to buy the September, 1936 issue of Popular Mechanincs and was fascinated by the plans for a one-tube regenerative radio that didn't need a B-battery, but operated on one 1 1/2 volt D cell and 6 volts from penlight batteries. I built it, using the 49 tube that was called for, and hand-winding four pug-in RF coils, which are wound on the outside of old salvaged large 4-pin tube bases. The base of the radio itself, where the tube and coil sockets are mounted, is a rectangle of pine wood, with an aluminum front panel. Old scrap radio parts made up the rest of the circuit, which is quite simple. Performance was weak to fairly good on the Broadcast band, but poor on shortwave. I decided that the 6 volts DC recommended for the B-plus was inadequate, so I doubled it to 12 volts. Stations then came in all over the vernier-drive dial on Broadcast and shortwave, but fewer over the higher shortwave frequency ranges. I finally settled on the 1 1/2 volts for the tube filament and 14 to 16 volts dc from AA penlight batteries in series for the B-plus. I used my 99 foot outdoor longwire antenna, 27 feet off the ground, to see what stations I could pick up. The headphones used are 1916-patent Baldwin Type C with mica diaphragms, about 3,000 ohms resistance. In a day or two, I was listening, at understandable volume and clarity, to the English Language service of Radio Pongyang in North Korea. This station came in at about 2:30 AM each morning. It was wintertime and that may have had a good effect on shortwave propagation. My location at that time was on the central California coast, about 90 miles south of San Francisco.
This set is easy to build and easy to operate. It uses a potentiometer to control the regeneration level, which is smoother and less tricky to adjust than RF coil feedback or capacitive feedback. Total battery power consumption is only 55 milliwatts!

Dan King

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Re: One-tube regenerative radio spans the Pacific Ocean

Post by Ragwire on Fri Oct 18, 2013 11:58 am

That's awesome! I've always loved the simplicity of the regen sets, and want to build a zinc oxide negative resistance regen receiver one of these days. No filament required...just a battery to make the zinc oxide device oscillate/amplify the signal.
(the sparkbangbuzz website has info on that.)
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Re: One-tube regenerative radio spans the Pacific Ocean

Post by N7ZAL on Fri Oct 18, 2013 11:33 pm

Very interesting. Schematic, pictures???
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One tube radio spans the Pacific Ocean, construction article

Post by dan88king on Sat Oct 19, 2013 11:38 pm

Unfortunately, I have misplaced my original magazine copy. I gave the wrong issue. The one-tube Am broadcast and 4 shortwave bands radio I built is from an article in the April, 1938 issue of Popular Mechanics. (The September, 1936 first article is an AM broadcast band only radio with only one plug-in coil.) I found that the correct magazine article is available at www.junkbox.com/electronics/lowvoltagetubes.shtml (it is under the heading "Print Articles on Low B+ Tube Technology, and the magazine article is entitled: One-Tube DX Short-Wave Set") and good sharp photos of the finished radio are on www.antiqueradios.com...t 64356&highlight=popular+mechanics  

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Re: One-tube regenerative radio spans the Pacific Ocean

Post by N7ZAL on Sun Oct 20, 2013 3:37 pm

Thanks Dan. Looks like a fun set to make and might have to give it a try. Oh, the second link didn't work for me but the article gave me all the info I need.
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One 49 tube homebrew pictures

Post by dan88king on Sun Oct 20, 2013 4:17 pm

Bill,
I also had trouble with that link. It worked at first, but after I sent the post, it wouldn't. I now type it all in on Yahoo Search or whatever you are using, leaving a space after the "t" instead of the equals sign, and it goes right to the website.
I don't think you will be diappointed with this project. The picures are worth seeing. I used a salvaged vernier drive tuning condenser, that as I remember, came from some junk piece of RF test equipment. It has a 0-100 dial and makes tuning in those weak shortwave stations easy. Instead of the 0-30 mmfd screw-type antenna trimmer cap that the original plans called for, I used one of the same or similar capacity, but mounted it at the rear right corner of the wood block and used an extension shaft with one of those round 1/4 inch universal shaft couplers, running through the front panel. Like the article mentions, it needs to be set to close to open. Everything else pretty much was salvaged components and hardware from the 1930's and '40s. I got the 49 tube and the tall coil form for the 110 to 200 meters from A.E.S., as well as the coil wire. Have fun!

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Re: One-tube regenerative radio spans the Pacific Ocean

Post by N7ZAL on Mon Oct 21, 2013 12:06 am

I did do a search of the link and they found the reference I think you referred to: http://www.antiqueradios.com/forums/viewtopic.php?t=64356

He did a very nice job on the unit. Certainly has my interest and I think I should have all the parts.
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