[Elecraft] K3 Audio/RFI Feedback

[Joe Subich, W4TV]

Do you have Mic+Line enabled in the K3? 

Sounds like RF on the cable between the K3 Line-Out 
and computer Line-In is being sent back to the K3 
Line In jack.  Improve the grounding of your station, 
including direct grounds on both the K3 and computer 
to the common ground point and add common mode chokes 
to both your feedline and the "Line In" connection to 
your computer. 

73, 

   ... Joe, W4TV 
   



> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net 
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bud 
> Governale, W3LL
> Sent: Tuesday, January 19, 2010 1:34 PM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] K3 Audio/RFI Feedback
> 
> 
> I'm experiencing audio/RFI feedback on 80M between the 
> frequencies of 3650 KHz to 3850 KHz using a full-size 80M 
> vertical 100' from the radio.
> SWR is under 2:1. No difference if I use the built-in ATU.
> 
> If I key the K3 and tap the mic once it goes into 
> motorboating with full output (100W).
> 
> The K3 monitor is set at 0.
> 
> If I mute the PC line-in sound card there is no motorboating 
> feedback. If I reduce the K3 mic setting from 30 toward 0 
> there is no motorboating feedback. If I reduce the PC line-in 
> volume setting toward 0 there is no motorboating feedback. If 
> I pull out the cable to the PC line-In there is no 
> motorboating feedback. If I pull out the cable to the PC 
> line-Out there is no motorboating feedback. At 50W setting 
> the motorboating starts but is not self sustaining. At 90W 
> setting the motorboating is self sustaining.
> 
> Any suggestions on where next to look - or a solution?
> 
> 73,
> 
> Bud W3LL
> w3ll at arrl.net
> 
> 
> 
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html