[Elecraft] K3: 6M SSB audio hash

[James C. Hall, MD]

Thanks Don:

I still suspect the 10' cable to the NCS Multi-Switcher is acting like an
antenna at that high a frequency - however, nothing changed with multiple
ferrite chokes along this line. Good idea to check the back mic connector,
although direct attachment of the hand mike and the headset to the front
connector did not cause the hash. The cable is a very well constructed cable
made by NCS for the K3 (Kenwood). I can certainly ask NCS (I forgot his
name, but he's very approachable) regarding the shielding characteristics. I
use the same cables for the other radios.

You asked if it gets worse with increase in power - yes, but not very much.
It's nearly an all or nothing deal.

When using my K2/100 with 6M transverter through the W2IHY unit, there is no
problem at all. The only difference is a longer cable to a different port on
the multi-switcher to reach the K3 - which is on the other side of my
monitor/desk.

73, Jamie
WB4YDL

-----Original Message-----
From: Don Wilhelm [mailto:w3fpr at embarqmail.com] 
Sent: Friday, June 06, 2008 5:17 PM
To: James C. Hall, MD
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3: 6M SSB audio hash

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
>   
>
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