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AR88 RCA MOD




 
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Author Topic: AR88 RCA MOD  (Read 350 times)
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KB5MD
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« on: September 25, 2018, 07:22:58 PM »

A simple mod for the AR88 RCA receiver that will greatly improve BFO use for SSB reception is to remove the twisted wire gimmick on the bfo
and replace it with a 100pf cap.  Just thought I would pass this along for anyone using the great old boat anchor.
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Joe Connor
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« Reply #1 on: September 25, 2018, 10:13:53 PM »

There's a good discussion of this issue in Henry Rogers' article on the AR-88 on the Radio Boulevard site. Just scroll down to Insufficient BFO Injection.

https://www.radioblvd.com/ar88.htm
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WD5JKO
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WD5JKO


« Reply #2 on: September 26, 2018, 02:00:05 PM »



As a former AR88 owner I looked into this issue as well. One consequence of increasing the BFO injection is that the BFO oscillator will "pull" in the presence of a strong AM signal. This can be both good and bad. The good part is that on a strong AM signal with QSB, the BFO may "Lock" to the IF frequency of the desired signal carrier. I think this is a form of "exalted carrier" reception. Other situations such as on SSB, the VFO may pull at the syllabic rate of the TX operator. This can sound pretty weird.

A higher injection can be good. Perhaps a BFO buffer stage could be used to minimize "pulling"?

Jim
Wd5JKO
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