[Elecraft] K3S Audio buzz on transmit, especially AM

[Nicklas Johnson]

I don't think that "collecting data" and "process of elimination" are
particularly ANTI-methodical either.  But the fact is that most people will
never encounter this kind of problem and don't spend their days practicing
how to troubleshoot it, so they seek advice from people who do have
experience.  Thus this email thread, which began with my thinking I'd
developed an audio fault in the rig and seeking advice, but successive
tests have pointed in other directions.

To answer Jim's earlier question, yes, it does appear that transmitting an
unmodulated AM carrier from the K3S into anything resembling an antenna
yields a buzz on the KX3 receiver (and vice-versa).  The buzz is NOT
audible when listening to the K3S's own TX monitor.

And to answer Frank's question, the PG&E transformer in our front yard for
the underground utilities is approximately 30 horizontal feet over and 6
vertical feet down from the station.  The distance to the utilities that
run through the back of our lot is approximately 60 feet.

I spent the morning reviewing (again) materials on grounding and bonding
over my morning coffee to see if there's something important I missed, and
I also found by repeating it that an earlier test I'd done had given me a
misleading/contradictory result-- transmitting into a dummy load
immediately adjacent the KX3 receiving it produces a nice, clean signal.  I
was misled before by the KX3 picking up a different buzz (probably off a
wall wart) in the shack when performing this test earlier.  (It also helped
in this case to put the KX3 into CW mode to detect the unmodulated AM
carrier.)

FWIW, this morning I also disconnected the bonding between the station's
ground rod and the house's utility power and also disconnected the DTV
antenna run into the house (which shares the same coax grounding/surge
protection bus outside, but of course could find another path to ground
over the coax shield via either one of the TV receivers).  Doing so
eliminated any *direct * connection with the utility power, as I'm still
running purely on battery power.  This had NO effect on the received buzz.

At this point I'm pretty sure this is an environmental issue and not a
problem with either rig, so it's probably not appropriate for me to
continue to pester the list about it.  Thank you again to everyone who
offered suggestions and advice.

But for posterity, and in case anyone comes along searching the list while
debugging a similar problem, here's a list of all the other things that I
tried to isolate the problem, none of which had any effect:

   - Complete disconnection of all other inputs and outputs on the K3S
   other than the antenna.
   - Turning off all nearby power supplies.
   - Setting the input to any other selection (front panel, rear panel,
   line in)
   - Setting the line input level to 0, verifying that front and rear panel
   gains were set to "low"
   - Running solely on battery power without the solar charge controller
   - TX EQ settings- cutting the low end completely
   - Taking the receiver outdoors, away from power supplies
   - Trying a different transmit antenna (ie, making sure I wasn't having
   problems with a damaged dipole having the house neutral wiring as one leg)
   - Temporarily disconnecting the station ground
   - Temporarily disconnecting the utility bonding from the station's
   ground rod
   - Reversing the direction: transmitting with the KX3 into a portable
   antenna and receiving with the K3S also produced a much more significant
   buzz

What DID yield some useful data:

   - Transmitting into a dummy load *while* turning off all nearby power
   supplies and lights with the KX3 immediately adjacent the dummy load: nice,
   pristine signal
   - Checking the TX monitor on the K3S: only white noise with the line
   input and the monitor output turned to maximum while transmitting.

What I have yet to do, and will require some more time and effort to
organize and implement:

   - Going portable or to another QTH to test again
   - Getting a signal report from a distant station to see if this is a
   local reception problem, or something actually getting into the transmitted
   signal.


   Nick


On Sat, 27 Apr 2019 at 01:19, Jim Brown <jim at audiosystemsgroup.com> wrote:

> On 4/26/2019 10:44 PM, donovanf at starpower.net wrote:
> > Y our emails leave the impression that your approach
> > isn't very methodical.
>
> Yes, but that lack of methodical troubleshooting is the result of most
> hams being weak on the fundamentals of fields and passive IM, instead
> seeing problems in the light of RFI and mythical concepts like "ground
> loops."
>
> The two causes I've come around to smelling in this problem are passive
> IM (which Frank reminded me of) and power-related fields. And Frank's
> advice is right on.
>
> 73, Jim K9YC
>
>
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-- 
*N6OL*
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