[Elecraft] K3 & Beringer HA400

[Steven Pituch]

Don and Dick,
It does not occur with "TX Test"  However, it is not any worse if I use my
ALS600 at 400 Watts, or I totally disconnect the amp and just use 50 Watts
out of the K3.

I think it is RF related, but only run into this problem with the HA400.  I
do run 450 Ohm ladder line into my shack up to my link coupled tuner but
just thought that it shouldn't happen to a proper design.

If I run with the front panel audio volume to zero and use the front phones
jack to the HA400 I get it bad if I plug the phones into the HA400 with the
HA400 volume set to about a 3.

I have the same problem with the line out.

If I disconnect the audio "IN" into the HA400.  I still get the buzz in the
phoes when I talk.  So it is RF getting into the HA400.

I wonder if some bypass caps in the HA400 might help.

Steve, W2MY





Message-----
From: Don Wilhelm [mailto:w3fpr at embarqmail.com] 
Sent: Monday, November 16, 2009 4:33 PM
To: Steven Pituch
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3 & Beringer HA400

Steve,

Just an idea - have you tried it on LINE OUT?  It may be that you are 
overdriving the input of the Beringer.
The other possibility is that you have an RF in the Shack problem and 
the Beringer is reacting to the RF.  Try it when connected to a dummy 
load or in TX TEST.  If that 'fixes' the problem, you have some antenna 
work to do to keep the stray RF out of the shack.

73,
Don W3FPR

Steven Pituch wrote:
> Hi All,
> I tried using these two items together and am getting scratchy audio in
the
> headphones when I speak on USB even though the monitor is set to zero.
When
> I use the rear headphones out to feed the HA400 it is really bad and loud.
> When I use the front headphone jack its medium loud but still not right.
It
> can be heard on my transmitted audio.
>
> I tried using a battery to power the HA400 to isolate the ground but it
has
> no effect.  I did the "Modification Improving the Immunity of the
Rear-Panel
> RS232 and Audio Connectors to RF" mod, and checked to be sure that the
> "Front Panel Microphone Circuit" mod had been done at the factory.  I
tried
> also using RG 174 for the audio feed.  No change.  I also removed the
serial
> cable and had no change.
>
> Any suggestions would be greatly appreciated as I do need to have four
> headsets on the K3 for various ham demos.
>
> 72 and thanks,
> Steve, W2MY
>
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