[Milsurplus] 500 Kc XMTR

Hubert Miller Kargo_cult at msn.com
Sat Sep 16 19:41:53 EDT 2017


Subject: Re: [Milsurplus] 500 Kc XMTR

Yes, that's it. I thought It would be a kick to have something like that on the air.
Years ago, at a PSARA meet in Seattle, this must have been around 1985, someone had a ship LF transmitter for sale. It was TBW-GO9 form-factor,
I mean narrow and tall, and tuned LF only. At the time I thought, wonderful, but what to do with such a thing? I couldn't justify it, and I'm sure it
became parts or just garbage.

I have a schematic for some Federal ( became Mackay, I think ) ship transmitter from the 1930s, and it shows, IIR, two tubes, one LF and one HF,
big tubes at around 1000 volts. I think okay on 600 meters, but what's that power VFO single tube going to sound like on the 12 MHz marine freqs?
-H

>Hue, you might be thinking of the RMCA ET-3650, a so-called "emergency" 
transmitter that ran 4 210s in parallel, in a Colpitts configuration, tunable 600 to 800 meters. I have a book titled "Practical Radio Communications" by Nilson and Hornung, 1935. It's in there, and it is powered by a 12V battery and a small motor-generator set, AC-CW at 700 cycles.

Looking at the main transmitters, the self-excited oscillator/amp circuits were common in the maritime service. A common configuration for non-emergency use would be a 203 (or 2 of them) as the oscillator, driving several more as amps in parallel, both MF and HF.

Interesting stuff, would love to get my hands one one, either HF or MF, just say I had it and used it.....

73, Howie WB2AWQ


On 9/16/2017 1:29 PM, Hubert Miller wrote:
> Remember that (probably) RMCA secondary 500 kHz transmitter that used 
> something like 4 triodes in parallel in self excited oscillator? This 
> was also in one Fair catalog one year. I sure wondered where on earth 
> they had found some of those. I had two close brushes with acquiring 
> one of those things. Once when I was rooting through a shed attic in 
> Seattle, which attice was piled about the knee high in every kind of 
> stuff, some very good stuff, but all interesting, up to your knees. I 
> put off dragging out that transmitter, and then with health problems 
> of the host owner, the invitations kind of faded away. Then there was one on Ebay and I communicated with the owner, but didn't move on it. I do have the matching receiver, it's something like AR-8501, which was also described in an AWA OTB article, so I probably should have acquired this transmitter. I never imagined that the LF band would be opened. The world moves on, and I'm continually surprised.
> -Hue




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