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Author Topic: Modulation Transformer ID  (Read 5134 times)
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KE6DF
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« on: April 29, 2010, 12:08:45 AM »
Does anyone know anything about the transmitter this modulation transformer comes from:

http://cgi.ebay.com/HIGH-POWER-120-WATT-MODULATION-TRANSFORMER-/370369562983?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item563bbf0967

There have be a few of them for sale on ebay recently.

* modtranny.jpg (75.1 KB, 800x977 - viewed 504 times.)
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KE6DF
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« Reply #1 on: April 29, 2010, 12:28:38 AM »
OK, I tracked it down myself.

It's from a GRT-3 air ground station VHF transmitter.

100W output

811's modulating a 4x150a

1950's ventage.

Turns out bama has a manual.

I would delete this topic, but I can't figure out how to do so.
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The Slab Bacon
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« Reply #2 on: April 29, 2010, 08:27:02 AM »
I picked one of those up at Berryville about 4 years ago for $2. We had a discussion a while back on here about it as W9LBB??, I think had one for sale.
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N4LTA
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« Reply #3 on: April 29, 2010, 08:57:30 AM »
I live about 20 miles from the seller. I sold one about 12 years ago at the Shelby fest that I took out of the SPA airport communication system when they removed the equipment.  Might be the same one.

I wish I had it back.
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WA1GFZ
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« Reply #4 on: April 29, 2010, 09:18:40 AM »
Hey, I have one also. Pretty large for 100 watts. I tried it on a Viking 2 once
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W2PFY
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« Reply #5 on: April 29, 2010, 10:08:29 AM »
Quote
I would delete this topic, but I can't figure out how to do so.

I'm glad you didn't delete it. I have one of those that's on an old DX-100 parts rig. Now I know what it is. I wonder what terminals  6-7-8 were for? Maybe to modulate a screen or to use as a driver for a class ab1 audio amp?
 
Thanks Grin Grin
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KE6DF
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« Reply #6 on: April 29, 2010, 10:54:27 AM »
"I wonder what terminals  6-7-8 were for?"

They are used for a limiter circuit.

See attached pages from the manual.
* GRT-3-Modulator.pdf (429.23 KB - downloaded 296 times.)
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WA1GFZ
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« Reply #7 on: April 29, 2010, 11:12:36 AM »
How much output power did this rig run?
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W2PFY
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« Reply #8 on: April 29, 2010, 11:29:30 AM »
Just downloaded the manual. The output is 100 watts 52 ohm load.  Over
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WA1GFZ
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« Reply #9 on: April 29, 2010, 12:29:25 PM »
I suppose that is MIL CCS watts not chicken band watts.
I bet that transformer would be nice in a Valiant.
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W2PFY
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« Reply #10 on: April 29, 2010, 02:53:57 PM »
It probably would run 24/7. It had an interesting 4 bay antenna the likes of which I never seen.

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