In article ,
Irv Finkleman wrote:


I am not as concerned about a case of 'rf lip' as I am
about stray RF causing possible problems with the
neighbours on all sides of me, with all my electronic
toys such as computers, DVD players, the local
fire-alarm system and other such things. The last
thing I want to do is draw attention to the fact that I
am running a ham radio station from my suite until
I know I am not causing any problems.

Thusly, my goal is to provide myself with a first rate
RF ground system, entirely contained within my suite,
in order that I do not wake up at night with the fire
alarms set off and great numbers of disturbed
residents gathered around pointing at me and saying
'Ham! Ham! For Shame! For Shame!' and the Residents
Council having special meetings to decide how to deal
with me. They already think I'm crazy -- and I may be
somewhat, but I don't want to make matters worse!

So, having herein explained my rational, lets see what
help I can get in the way of producing the ideal indoor
low-cost non-radiating counterpoise radial system.

Irv,

Your goals are certainly valid.

As far as preventing RF from going where you don't want it to... the
main issue MJF is talking about here is "conducted" RF. The RF energy
on the "ground" side of your antenna connector is going to flow
outwards through every conductive path available to it, including the
"counterpoise" side of your antenna arrangement, and anything
connected directly or indirectly to your rig's chassis (e.g. to the
power supply and then onto the third "ground" wire in the household
mains). The amount of current flowing through each of these paths
will depend on the RF impedance of the path, with more current flowing
through paths of lower impedance.

So, what you want is (probably) to have one or more counterpoise wires
whose RF impedance is as low as practical, at the frequency in
question. These could be quarter-wave wires, or they could be shorter
or longer wires with an "active ground" (which is essentially a simple
"antenna tuner" on the ground side, with an adjustable reactance to
cancel out some of the reactance of a non-quarterwave wire).

You can also help keep RF "where it belongs" by adding common-mode
chokes to your rig power cables, thus increasing the RF impedance of
this path and helping reduce the amount of current which is conducted
back into the building ground.

Another approach which may help, is to consider using an end-fed
half-wave antenna, with a specifically-wound matching coil system.
These are (in principle at least) largely ground-independent... the
low-impedance side of the matching coil provides good RF paths for
both the "hot" and "ground" sides of the antenna connection, and when
properly adjusted they don't dump much RF into the rig ground or
counterpoise.

These techniques may not help much, if at all, with *radiated* RF
getting into places you don't want it. Even if you have an antenna
which is fully balanced, and completely isolated from the building
ground (e.g. battery powered), the "near field" RF from the antenna
can be coupled into the building wiring, and start causing
interference and "undesired operation". Unfortunately, a lot of
consumer and industrial electronic equipment these days is very
vulnerable to this... poor shielding/filtering. Speaker cables,
telephone and alarm wiring, etc. can all act as antennas.

Not much you can do about this except try to route your antenna and
counterpoise wires as far away from other wiring as possible, keep
your transmission power down, and try to transmit during times when
people are asleep.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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