Correct. My K3 was the first one to have the stiffener. I discovered the
microphonic synthesizer early on (2008 IIRC) and demonstrated it to an Elecraft
engineer in my shack. His radio had the same problem. It didn't take high
levels, noises in the shack would modulate it; they were more random and harder
to see than single frequencies, but they were there.
Of course the new upgraded boards are free of this.
Considering the lightweight construction, the almost total lack of shielding and
the questionable TMP connectors, the K3(S) is remarkably free of birdies and
spurious garbage. It's there just usually not objectionable.
Wes N7WS
On 1/1/2021 3:36 PM, Mike Harris via Elecraft wrote:
I believe the rather thick "shield" was actually a stiffener to prevent
microphony at high audio levels using the internal speaker.
Regards,
Mike VP8NO
On 01/01/2021 18:22, g4piq--- via Elecraft wrote:
And a small correction to this in case anyone else gets inspired to do
anything. Grounding just one of the crystals improved the performance by
about 8dB - but did not get as good as the KSYN3 with a shield. It clearly
needs the full treatment.
73,
Andy, G4PIQ
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