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Re: [RFI] KW Amp on second floor

To: <rfi@contesting.com>, "N6KJ" <kelly@thejohnsons.ws>
Subject: Re: [RFI] KW Amp on second floor
From: "Tom Rauch" <w8ji@contesting.com>
Reply-to: Tom Rauch <w8ji@contesting.com>
Date: Fri, 12 Mar 2004 06:00:53 -0500
List-post: <mailto:rfi@contesting.com>
> I'm considering buying my first amplifier (after almost 30 years
barefoot).
> I've always heard that running your rig from the 2nd floor of your house
> is risky because you can't get a good ground.

The idea you need an "RF ground" on equipment is largely a myth brought
about because people insist on feeding antennas incorrectly. If you have a
reasonably proper antenna installation there is virtually zero RF on the
cabinets anyway, unless you use a single wire feeder.

What people often do is sometimes insist on feedline a dipole with
unbalanced line, a vertical with much less than perfect ground with coax, or
bringing a feeder away from an antenna in parallel with the radiator and NOT
using a choking device to remove common mode currents.

Then of course they get the notion that the earth terminal of the gear needs
an RF ground, because they have problems.

You need a low frequency safety ground for power mains, but there is no way
anyone needs an RF ground on equipment with halfway decent shielding and
coaxial or properly balanced two-wire output. You need a lightning ground at
the power line and antenna entrance to the building that is common to
everything, but RF grounds belong at the antenna...not in the house.

The exception to this is if your equipment, feedlines, or antennas are
poorly maintained, designed, or installed. (Say for example you don't solder
shield connections.)

73 Tom


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