[TenTec] Does this happen to you on transmit...OMNI V ??
k9yc at audiosystemsgroup.com
Tue Feb 25 01:16:58 EST 2014
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
73, Jim K9YC
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