On Tue,3/22/2016 4:50 AM, george allen wrote:
> RF is getting into your equipment.
While this is not the only possible cause, it's likely. Other possible
causes include a bad piece of coax or bad DC wiring.
> RF split cores on all leads into your 2820 should solve the problem.
If the problem is simple overload of the 2820, what is needed is NOT
simply slipping a split core over the coax from the 2820, but rather
multiple turns of the coax through a #31 or #43 Fair-Rite core. That
could be a split core or a toroid. If it's a split core, five turns is a
good start for 40-10M, one or two more if the problem is from 75M. If
it's a toroid, I would start with 5 turns for 20-10, 7 turns for 40-15,
10 turns for 80-20.
Also, think about antenna locations. Are the HF antennas and 2M antennas
close together? Separating them a bit could help. And the HF antennas
should all have a multi-turn coax choke at their feedpoint (that is, up
in the air).
RF interference is NOT solved by a connection to earth. RF interference
CAN be solved or reduced by bonding together every piece of gear in the
shack with short, fat copper. That combination of chassis DOES need a
bond to all other grounds in the building, both for safety and for
reduction of hum, buzz, and RFI.
And even though John said he had "checked" all the coax, a bad piece of
coax (either the cable or the shield connections) should be suspected as
a possible cause.
Study
http://k9yc.com/GroundingAndAudio.pdf for lots of detail on this.
And study k9yc.com/RFI-Ham.pdf for a tutorial on how RF gets into
equipment, how ferrite chokes work, and how many turns on which ferrite
cores to use for different situations.
73, Jim K9YC
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