[Elecraft] [K3][Speaker Out interaction with Line Out?]

[Edward R. Cole]

Sounds like you still have some RF getting in on the speaker cables 
or maybe on the line-out cables.  How much power do you run in 
JT-65HF?  I run JT-65 on 144-MHz at 1400w with no issues like you 
have.  I do not use a powered/amplified speaker, just and old 
National speaker console from the 1950's with plain speaker wire.  My 
line-in and line-out cables are standard shielded audio patch cords 
from RS. But then I only run 1.5mw to my transverter on 28-MHz, so no 
significant RF coming out of the K3.

A quick test would be adding a .001 uF disc. ceramic bypass cap from 
the center wire to ground at the K3 on the speaker.  The toroid 
apparently is helping according to what you write.  Maybe shielded 
speaker wire would help?  I would guess the audio is already 
transformer coupled to the K3 speaker output so an isolation 
transformer probably would not help.  I do think this looks like RFI.


73, Ed - KL7UW, WD2XSH/45
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