[Elecraft] K3: 6M SSB audio hash

[Don Wilhelm]

Jamie,

The Heil headset will plug directly into the rear panel jacks - why not 
give that a try as an added piece of evidence that it is not the microphone.

Most likely, something is being picked up on those long microphone 
cables and is not a K3 problem at all.  Are all the mic cables 
shielded?  Are all the cable shields connected to the plug/jack shell?  
They should be.

I have not investigated the W2IHY equipment, but my understanding is 
that it is setup primarily for pro mics which use balanced AF lines for 
the mic audio.  My suspicion is that there is something awry with the 
balanced to unbalanced arrangement when used with unbalanced line 
microphones such as you have there.

As far as why it shows up only when the PA turns on, I can only 
speculate there too, but remember that there is more gain in the 
transmit stages when the PA turns on, and that added gain may make any 
small AF line pickup more pronounced in your transmit signal.  If it 
were from RF coupling into the audio, it would vary smoothly from low 
power to high power and all RF levels in between - you indicated only 
that it was there with the PA on, but did not say that it got worse as 
power was increased.

73,
Don W3FPR

James C. Hall, MD wrote:
> Bob:
>
>  
>
> As a follow up, I doubt it's the Goldline mic/cable itself, as I get the
> same hash with a Heil headset plugged into the switcher. 
>
>  
>
> 73, Jamie
>
> WB4YDL
>
>  
>
>
> From: James C. Hall, MD [mailto:nwtcc at earthlink.net]
> Sent: Friday, June 6, 2008 04:27 PM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] K3: 6M SSB audio hash
>
> Hello: I've noticed some audio hash on my SSB signal on 6M only when the PA
> relay kicks in at 13 watts. My long microphone cable goes to a
> Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil Goldline microphone.
> This completely disappears when I use a Kenwood hand mike direct to the K3.
> Thinking that this was a classic "RF on the line" problem, I clipped on
> multiple ferrite chokes with many turns on the cable coming from the K3, the
> Goldline mike, and in between the switcher on noise gate. This didn't even
> slow it down ! Hmmm. Interestingly when the PA relay is off at 8 watts,
> there is absolutely no hash. For now, I'll just use the hand mike on 6M
> (which requires a bit more mike gain) to keep a clean signal. Has anyone
> else noticed this ? Got a solution ? 73, Jamie WB4YDL
>   
>