On 5/28/2011 2:27 PM, Magnus Aronsson wrote:
> I have some HF problems.
Several thoughts.
First, virtually ALL computer sound cards, and virtually ALL powered
speakers are notorious for being RFI DOGS. SERIOUS multi-turn ferrite
chokes on audio cables and serious DC bonding from chassis to chassis of
all of the gear in your shack can help keep RFI and noise out of your
computer.
Second, I would suspect some sort of problem in the AC POWER wiring.
Something as simple (but REALLY BAD) as reversal of black and white (or
white and green) an one or more power outlets. Maybe you didn't re-wire
anything to move your station, but maybe you're plugged in to different
outlets than you were before, and they were bad from the beginning.
Remember that all power wiring is done by human beings, and, as a race,
we screw up. :)
Third, be sure that there is VERY SOLID bonding between your rigs, the
AC power system, and EVERY ground in your home. (A BOND is simply a
very robust, big, short connection between grounded objects). This sort
of thing is REQUIRED by building safety codes in virtually all of the
developed world. Not only does it make things more SAFE, it also greatly
reduces problems with RFI, hum, buzz, and other forms of noise.
Fourth, use robust coax chokes at the feedpoints (that is, up in the
air) of all antennas to keep RF off the coax. This helps with RFI, and
it also minimizes the RF noise that the antenna hears.
For more detailed advice, study the tutorials at
http://audiosystemsgroup.com/publish.htm especially the one on RFI
and ham radio. Study the chapter on Solving Problems in the Shack, and
see the section on coax chokes for details on that. Also study the
beginning stuff to understand how RFI happens.
73, Jim Brown K9YC
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