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1935 RCA 100F Ultra-Shortwave AM transmitter




 
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Author Topic: 1935 RCA 100F Ultra-Shortwave AM transmitter  (Read 7906 times)
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W7TFO
WTF-OVER in 7 land Dennis
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« on: October 19, 2012, 09:39:52 PM »

I finally got to get some photos.  It is really nicely made job, copper chassis and all.  

4 ea. 800 finals, modded by a pair of 838's.  Was built to carry out to 17.5 Kc audio, used at KNX in Los Angeles as part of the FCC 'Apex" project.

http://www.theradiohistorian.org/Apex/Apex1.htm

Too bad it was hamboned down to 80m at some time in it's life with a homebrew heterodyne oscillator and a BC-610 tank coil.

I hope to restore it to year one, and if anyone has some lit on it I'd really appreciate a copy!

73DG


* DSC01580.JPG (142.07 KB, 640x480 - viewed 594 times.)

* DSC01578.JPG (149.02 KB, 640x480 - viewed 664 times.)
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W7TFO
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« Reply #1 on: October 19, 2012, 09:40:56 PM »

More pix:


* DSC01585.JPG (153.85 KB, 640x480 - viewed 593 times.)

* DSC01586.JPG (151.84 KB, 640x480 - viewed 555 times.)
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W7TFO
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« Reply #2 on: October 19, 2012, 09:42:53 PM »

And again:


* DSC01581.JPG (150.46 KB, 480x640 - viewed 529 times.)

* DSC01582.JPG (154.08 KB, 480x640 - viewed 555 times.)

* DSC01587.JPG (151.58 KB, 640x480 - viewed 586 times.)
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Opcom
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« Reply #3 on: October 19, 2012, 09:43:34 PM »

wow! That's a real beauty! I love that mercury relay!
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W7TFO
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« Reply #4 on: October 19, 2012, 09:46:57 PM »

Not a mercury relay, rather an oil-damped dashpot time delay.

73DG
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K5WLF
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« Reply #5 on: October 20, 2012, 04:23:40 AM »

That is pretty. Love the pic of the laced wiring in the first post. That's the way rigs should look.
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« Reply #6 on: October 20, 2012, 11:35:39 AM »

Not a mercury relay, rather an oil-damped dashpot time delay.

73DG

more better. What band was it on before the debauchery?
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W7TFO
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« Reply #7 on: October 20, 2012, 12:02:15 PM »

Not a mercury relay, rather an oil-damped dashpot time delay.

73DG

more better. What band was it on before the debauchery?

From 30 to 41 Mc.

73DG
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KM1H
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« Reply #8 on: October 20, 2012, 12:34:20 PM »

Quote
From 30 to 41 Mc.

And it covered it all during a broadcast Grin
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W2PFY
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« Reply #9 on: October 20, 2012, 12:39:17 PM »

Not a mercury relay, rather an oil-damped dashpot time delay.

73DG

Is that some sort of overload relay? My big Westinghouse has one of them thar relays. I have an extra one as well but never looked into their operation.
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Steve - K4HX
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« Reply #10 on: October 20, 2012, 12:43:17 PM »

More less like a shock absorber that produces some sort of time delay for turn-on/turn-off.
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W7TFO
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« Reply #11 on: October 20, 2012, 12:47:27 PM »

They magnetically pull a calibrated plunger through what looks like 30-W oil to effect the delay before letting the contacts operate.  

The cylinder on the bottom is where it happens, and usually you can set the delay by screwing it up or down.  The plunger has a one-way valve to allow quick reset when de-energized.

They always seem to leak a bit of oil.

73DG
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W7TFO
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« Reply #12 on: October 20, 2012, 12:52:06 PM »

Quote
From 30 to 41 Mc.

And it covered it all during a broadcast Grin

Well, it was built for wideband AM Hi-Fi and not just PTT communication.

Oscillator drift up that high was another matter altogether.

It was all about Sarnoff not wanting to go with Armstrong's FM & patents apparently.  The history surrounding the APEX project is slight, but very interesting.

73DG
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« Reply #13 on: October 20, 2012, 01:14:52 PM »

As a matter of fact I recall that my Westinghouse was shipped dry and I had to add the oil  to it. It had a screw on cap on the can and looked like dirty oil but it was probably because the oil was from 1956.

Along the same lines, I have somewhere the output coil & link from a 1941 GE BC transmitter that used two 833A tubes on the early FM band that was driven by two 810's. I still have the book on it and I actually talked with the engineer who worked on it. He said they were constantly replacing the 833A's.
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« Reply #14 on: August 27, 2023, 11:00:32 PM »

Research has indicated my 100F was not part of KNX, rather another operation in LA.

73DG
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« Reply #15 on: August 28, 2023, 12:06:58 PM »

Research has indicated my 100F was not part of KNX, rather another operation in LA.

73DG

a conversion to 20meters would make you the Lighthouse station of 14.330. Grin
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W7TFO
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« Reply #16 on: August 28, 2023, 12:31:09 PM »

Since it is designed to work at high HF, I thought it would be a perfect candidate for 11M.

73DG
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