That ground screw on the rear is also used on the inside to connect the DC
negative to chassis. It then protrudes to the outside for the radio ground
terminal.
73
Bob, K4TAX
----- Original Message -----
From: "Jim Brown" <k9yc@audiosystemsgroup.com>
To: <tentec@contesting.com>
Sent: Tuesday, February 25, 2014 12:16 AM
Subject: Re: [TenTec] Does this happen to you on transmit...OMNI V ??
On 2/24/2014 6:28 PM, Bob McGraw - K4TAX wrote:
Make sure the ground screw on the rear is very tight.
The earth is NOT a sump into which RFI and noise can be poured. A
connection to earth is almost never part of a solution to these problems,
nor does it make an antenna work better. What DOES matter, and matter a
LOT, is that all cable shields go DIRECTLY to the SHIELDING ENCLOSURE. If
it's a transmission line, it DOES NOT MATTER if that enclosure has a
connection to earth.
It IS important for all shielding enclosures in a station to be bonded
together by short fat copper, both for baseband noise reduction, and for
lightning safety. And for lightning protection ONLY, that stuff needs a
good connection to earth.
The only RF purpose of that grounding screw is for the connection of a
counterpoise for an antenna that is loaded as an end fed wire that ends in
the shack.
I can think of two situations in which a connection to earth helps noise,
both at AF and RF. 1) There is AF or RF noise on the neutral feeder from
the power company. The connection of neutral to the green wire and to
earth diverts that noise into the earth and away from grounded conductors
in the home/shack. 2) A common mode low pass filter is formed by a series
choke and a connection to earth of a coax shield on the noise source side
of the choke. With a 2-wire line, a balanced capacitive connection to
earth would be used. This can divert common mode noise to the earth, but
without the choke, it would be of little value.
73, Jim K9YC
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