[RFI] Computer RFI problem

[n5tu@wt.net (Earl Morse)]

Jamie,

I am willing to bet that your RFI problem is a proximity issue.  I have the
same thing.   A tribander 50 feet above the shack and the same tribander on
a second tower located 100 feet away and 100 feet up.  The distant antenna
is quieter and cannot hear any of the local computer rfi that the close
antenna can.  Computer RFI is generally very weak with the standards for
measuring it requiring short antennas distances.  Signal strength is
inversely proportional to distance so the farther you go the weaker it gets.

Earl


From: "James C. Hall, MD" <nwtncc@iswt.com>
To: <rfi@contesting.com>
To: <rfi@contesting.com>
Date: Sat, 3 Aug 2002 17:28:48 -0500
Subject: [RFI] Computer RFI problem

Here is an interesting problem:

I put up an old Cushcraft R-7000 on the roof as a secondary antenna. My
primary antennae are on a tower 150 feet from the shack and perform very
well without RFI difficulties. When receiving with the vertical on 20
meters, I hear S9 computer generated interference. Changing antennas to
either the beam or an inverted V yields no such interference. This only
occurs on 20 meters - at least very audibly - and only with the vertical.  I
used to have trouble with the lower frequency bands ie. 75/80 meters until I
switched out the computer power supply with a better filtered and shielded
one. Now no problem on those bands.

I'm thinking about adding some length to the coax off the vertical to see if
that would help ... but I doubt it.

Any ideas ?

Thanks,

Jamie
WB4YDL