[Elecraft] Monitor noise

[Vic Rosenthal]

pjhend@ameritech.net wrote:
> 
> I'm nearing the end of my rope.......
> I've been trying to "noodle through" the problem of horrible noise to my
> K2(and other HF rigs) from my Compaq Presario MV500 computer monitor.

Instead of worrying about the generation and radiation of RF by the monitor,
let's look at how it's getting into your receivers.  What kind of antennas do
you have?  An end-fed wire coming into your shack will always be prone to pick
up RFI.  The most RFI-resistant antennas are:

1) A balanced antenna fed with balanced line and tuned with a true balanced
tuner.

2) A balanced antenna fed with coax with a balun at the feedpoint (the balun
stops RFI flowing on the feedline from getting into the antenna itself).

3) An unbalanced antenna such as a vertical fed with adequate decoupling at the
feedpoint.

The idea is to get the antenna away from the shack, and -- once the antenna
itself will not pick up the RFI -- prevent RFI that is picked up in common mode
on the feedline (which of course has to be near the interference source) from
getting back into the antenna.

It's a myth that coax is more immune to RFI than balanced line.  Both will work
fine if used properly, and both will pick up RFI if not.  In either case, the
trick is to prevent common-mode currents from flowing up to the antenna and
thence down to your rig.

Vic K2VCO
Fresno CA