> My 2 cents on the '757. I had one for a short time several years
> ago (ex-CB
> pawn shop special)
>
> Although the raw performance was poor, the quality of the received signals
> seemed quite good. A big part of its subjective quality was due to the AGC
> characteristics -- its "delayed AGC" did not pump up the noise
> floor, giving
> the impression of very quiet receiver (as long as the band was
> not crowded).
> Many receivers of that era had too much overall gain and 100+ dB of AGC
> range -- great for ragchewing, lousy for DX and contests!
>
> 73, Gary
> K9AY
When I got my FT757 20 years ago, I was immediately disappointed
by the low gain and lack of AGC action. I added 20 dB of gain to
the 8 MHz IF. This was very helpful on 10 and 15 meters, especially
when using a vertical antenna. On the lower bands, it allowed me
to never use the preamp and often turn on the attenuator.
However, I did encounter what Gary was talking about. If I turned
on the preamp after this mod, it would make signals less intelligible
due to the AGC pumping unless I turned down the RF gain.
More recently, I ran into this problem on my FT-1000D. A beverage
will sound real "quiet" because of its low gain. I can get fooled
into thinking the beverage is better than some reference antenna
that has normal gain due to AGC pumping. The fix for this is to
put a 10 or 20 dB attenuator on the reference antenna so that the
absolute signal power is the same. THEN I can really see if the
beverage has better S/N ratio. Sometimes the beverage is a big
improvement, but sometimes not.
I can easily see how in comparing two radios (such as a stock 757
vs my modified 757) you could think that one was much better
simply because of these AGC effects, which can be mitigated. Most
radios will sound better to the casual listener if the RF gain
is decreased to where the AGC is inactive. Thus one has to be
extremely careful in making comparisons by ear. Letting the radio's
owner adjust the radio might be helpful, but only if the owner
is good at adjusting radios. There is no guarantee of this.
Rick N6RK
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