[ARC5] Receiver Tube Substitution

[WA5CAB at cs.com]

Ken,

In a message dated 12/18/2016 11:47:14 AM Central Standard Time, 
kgordon2006 at frontier.com writes: 
> As another example and one which I have mentioned here or elsewhere a 
> time or two 
> before this,  many years ago, I was given or traded for an essentially new 
> BC-779, with 
> power supply. The BC-779 has two RF amp stages ahead of the 6SA7, which as 
> you state 
> is a very noisy mixer. (As an aside, the only mixer which is MORE noisy is 
> the 6/12K8 which 
> is used in our ARC-5s).

The BC-779 uses a 6L7 Mixer with a 6J7 HF osc.  Despite looking new, it 
must have already been hacked.

> 
> Anyway, my "new" BC-779 had a very serious problem in that the BFO 
> injection was so low 
> that even when receiving fairly weak CW signals, the signal would overcome 
> the BFO which 
> made it very hard to copy CW.

That isn't normally the case.  Whomever modified the mixer stage may have 
also screwed up the detector and BFO circuit.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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