It was the (international!) law, but it would have been a good idea even if it hadn't been required: beginning in 1929, radio amateurs had to build their transmitter to meet nominal requirements for stability and spectral purity.
The rules weren't especially stringent; existing designs could be adapted and a beginner's transmitter wouldn't cost any more, though it might take more time to adjust. The benefit was that sharp, stable signals get through where wobbly, "squeggy" ones would prove too hard to read.
...It happens that for radiotelegraphy, a "1929 type" transmitter still makes signals stable enough and clean enough for amateur use. Even if the other ham is running a software-based radio on a plug-in computer card, he (or she) can tune it in.
And you can build one! Canadian ham VE7SL shows how, complete with original schematic, recent photos, modern schematic and ways to couple it into your coax-fed antenna, and then ends with a photographic round-up of 1929-style breadboard rigs by a dozen-odd builders. (And if you'd rather build Ross Hull's wonderful 1929 Hartley, why, he'll show you that one, too!)
I'm going to have dust mine off. H'mm, I need to find me a type '45 or '10 transmitting tube.*
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* The ' in place of a first digit replaces the manufacture's ID number -- "2" for RCA, for example.
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Good post. Thank you for exposing us to a bit more of our history.
ReplyDeleteGod Bless Ya'll!
Aggie, Class of '70
An Anglican Firearms "Enthusiast" (ie: Gun Nut)
www.ananglicangn.blogspot.com/
Pretty neat stuff, although not *quite* the type of homebrew I do.
ReplyDelete"Electric Radio" magazine is also a good source of articles on old radio things.
Beware, though, that if you order a few back issues and a subscription, you'll be buying the complete set of back issues just because some of the writing is so good!
http://www.ermag.com/
Yes a great post on some of the history.
ReplyDeleteI"e actually heard the people running older radios like the '29s and hartlys during SKN. Some sounded very good.
Allison/kb1gmx
My first tube radio was a 6SL6 circuit built on a planed 2X8 board. It didn't work the first time out, but it won acclaim anyway. It seems the 'breadboard' turned out to be our Principal's erstwhile 'Board of Education'. My pal had stolen it, trimmed off the handle, and gave me the rest of it when I needed a base. I was absolved of any wrongdoing. I had never even SEEN the paddle, and I hardly would have paraded it as a project.
ReplyDeleteBut that board would have been a sweet base for a '29' project.
Hmmmmm, I need to get some 4, and 5 pin sockets.
correction that were a 6L6G tube as in the QRP-40.
ReplyDelete