At 20:30 15/11/1998 -0700, Milt N5IA wrote:
>
>An amateur friend of mine recently started getting back into HF after a
>number of years of absence. In setting up his station he has encountered a
>severe case of RFI associated with the monitor. It is particularly bad on
>160 meters (snip)
>
Just got back from overseas, hence the delay.
Make sure the monitor uses a power cable which plugs into the PC, not a
separate wall outlet. This will confine the monitor RFI currents to the
loop between the PC and monitor, and prevent them getting onto the mains
wiring from which they will radiate more efficiently.
Connect together the case of the PC, TX/RX, other station equipment, and
local AC power ground. I use a length of 90 degree brass angle running
along the rear of the operating desk, with everything connected to it
through a short length of wire.
Fit a 1:1 toroidal balun at each end of the feedline, to suppress common
mode currents. A few large clip-on ferrites spaced along the coax are also
worthwhile. These will prevent any local RFI currents, which have coupled
onto the feedline inside the shack, from being conducted out to the antenna.
I implemented these measures a couple of years ago as part of a larger
program to get RF out of the PC, and was pleasantly surprised to see a
significant drop in the level of noise received from the computer and
monitor, AC power line, and various domestic appliances.
73,
Peter VK3APN
pnesbit@melbpc.org.au
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