Greetings all:
The location of the transceiver radio, Pegasus, to the computer has nothing
to do with the computer noise received in the radio! The noise in the
radio, Pegasus or what ever, is solely related to the Antenna and the
Computer and the relationship between them.
If you have computer interference with Radio "A" then if nothing else
changes you will have computer interference with Radio "B". If the computer
is effectively decoupled with the Antennas then you will not have
interference.
How does computer noise get to the antenna?
1. A single wire fed antenna brought into the shack to a local antenna
matching system will pick up local computer noise the quickest.
2. A well balanced open wire feed line brought into the shack will help
somewhat in keeping computer noise down. If you tie the open wire ends
together to get on a lower band, all noise reduction due to "balance" is
gone.
3. A coax fed antenna brought into the shack can be a real nasty as the
computer noise has great opportunities to run up the outside of the coax to
get into the antenna. A ferrite decoupler or a coil of coax acting as a
choke will help stop this when done right.
Here at my Island QTH my antennas are all out back on the other side of the
Island, some 400 to 700 feet away. I use hard-line for my feedlines and I
NEVER hear any interference from the five different computers here at the
moment. One trick I use is to run the feedline underwater for as much as I
can, I have found this acts as an excellent choke at RF frequencies that
just might be riding on the outside of the coax. Keeping computer noise out
of the HF radios is solved, so is the effect of High Power HF operation on
the local TV set. The TV has one of those awful super duper high gain and
wideband RF amplifiers which can hear "the grass grow" and voila no
interference at all.
Summary, the radio has nothing to do with hearing local computer noise, the
antenna and its feedline are the issues.
Hope this helps with any confusion in this area
Larry
PS The picture of the DSP Radio on Page 33 of September QST sitting beside
the portable PC was not for listening to 2 Meter FM signals with the rubber
duck antenna. This physical configuration was for listening to the noise
from the portable computer! The picture configuration does little to help
bring understanding and expectation setting for those who have not been
through the microprocessor revolution since the beginning in 1972. Frankly
I would expect better attention to detail in QST myself.
--
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