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Collins S line transmitter on AM




 
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Author Topic: Collins S line transmitter on AM  (Read 646 times)
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w4bfs
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« on: March 25, 2017, 12:09:46 PM »

Has anyone satisfactorally done this ?  How cleanly can it be done ?
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Beefus

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W4DNR
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« Reply #1 on: March 26, 2017, 12:29:29 AM »



Without a lot of hacks, you should be able to open the screen circuit ( two rca jacks on back that open the 6146 screen circuit when used with the 62S1 Vhf converter ) and modulate the screen.

A deeper mod without going inside the S-line might be to use a couple of  male and female in-line multi-pins to open the plate voltage between the 516F2 power supply and the transmitter.  Plate modulate the HV in the CW position with an external modulator.

If you want to use the S-line audio chain, it would require bypassing the mechanical filters if you wanted double sideband.     

Don W4DNR
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« Reply #2 on: March 26, 2017, 08:55:52 AM »


Beefus,

   Perhaps try something similar to what fellow member Georgio IN3IEX did to his Drake T4XB:

http://www.ing.unitn.it/~fontana/TrueAMT4XB.pdf

Jim
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« Reply #3 on: March 26, 2017, 03:02:05 PM »

QST April 1962. pages 38 and 39 has an article on adding AM to the S-line and the KWM-2.  Have not done this, but thought it might be helpful to you.
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73,  Mitch

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« Reply #4 on: March 26, 2017, 11:04:39 PM »

Has anyone satisfactorally done this ?  How cleanly can it be done ?

I once worked a guy who had opened the screen supply and placed the high-Z side of an 8 ohm to 10 kilohm audio transformer in series with it. (I think it was a 10-Watt tube audio amp output transformer wired up backwards.) He then connected a small hi-fi amp's speaker output to the 8 ohm side -- and the resulting AM sounded superb. I believe he may have reduced the bypass capacitance on the screens somewhat, but it's been a few years so no numbers come to mind. I am not sure what adjustments had to made as far as drive, loading, and screen voltage were, though.

73,

Kevin, WB4AIO.
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« Reply #5 on: March 27, 2017, 12:01:45 PM »

Quote

I once worked a guy who had opened the screen supply and placed the high-Z side of an 8 ohm to 10 kilohm audio transformer in series with it. (I think it was a 10-Watt tube audio amp output transformer wired up backwards.)
73,

Kevin, WB4AIO.

Easy to do ..... clip one wire between two of the rca jacks on the rear panel.

Don W4DNR
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« Reply #6 on: March 28, 2017, 11:25:59 AM »

thanks to all for some interesting ideas .... found both QST citations (with difficulty) from 1961 ....keep those cards and letters comming ....
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Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
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