[Elecraft] K3 Tx Spurious on Specific Frequencies on 160/80/40

[Wes]

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