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Old 18th Nov 2017, 6:55 pm   #8
Keith
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Join Date: Jan 2003
Location: Tewkesbury, Gloucestershire, UK.
Posts: 690
Default Re: R209 - BFO injection

Hi Peter/Don,

The BFO does work but requires the gain to be drastically reduced to resolve SSB. I've also measured the BFO level at the IF output. I get almost 2Vpp. I've now paralled C88 with 33pF and this brings it up to ~4Vpp, which improves things somewhat. I've also (reversibly) disconnected the Scott T CW filter which gives a better sounding result on SSB (it didn't actually seem that sharp when it was in circuit so presumably the high value Rs have drifted somewhat).

The IF output is completely one sided due to it being taken from the anode (grid in this case) of the detector. Presumably that was good enough for the FSK detector.

All in all, not a bad RX for AM although the audio from the waterproof speaker is very boxy - much better on phones.
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