Readers may recall that I posted a query a few weeks ago about whether =
or not to=20
tie my radials to a ground rod at the point where I am feeding the =
antenna through a=20
matching network.
My antenna is in an upside down "C" configuration with a wire length of =
approx 145ft.
I feed it through a 500pf variable capacitor that brings the wire to a =
low SWR at 1.815khz=20
with about 330pf. Since the antenna is fed through the capacitor it is =
essentially "floating"
with no DC connection to ground. I have 12 on ground radials of various =
random lengths
none of which can exceed about 60 ft in order to stay with in the =
boundaries of my city lot. =20
I also have 4 elevated radials about 7-8ft above the ground and roughly =
the same length=20
as the on ground ones. All of these were tied to a 6ft copper ground =
rod. The cap is in a=20
weather proof case and the metal case was bonded to the rod by a piece =
of coax braid about=20
a foot long.
I saw a note on the OK1RR website that said not to tie radials to a =
ground rod so a few days ago I lifted
the radials off the rod and played with the antenna for a few days. I =
have a FSM in the shack and I did=20
notice that the FSM deflection did go up but very slightly but not =
significantly. I plan to do further
A/B test with a friend a mile away and see if he can see anything on his =
meter.
The surprise is that I found the noise that I was hearing on 160M has =
decreased noticeably.
I am using a coax loop rx antenna that is in the field of the radials. =
The loop is fed into an ARA
prepamp which is indoors and right at the RX ANT IN jack of the MP. =
Signal levels on most stations=20
and nites are the same on the loop as on the wire antenna. Since =
removing the ground rod the noise
that I was hearing on the loop has gone down. I can't quantify this is =
terms of DB but it has definitely
decreased. So did the ground rod removal contribute to this or has the =
noise level gone down in the=20
neighbourhood??
Also since the wire is fed through a series variable cap it is =
"floating " and unable to discharge any static build up
from rain or snow or passing meteorites etc so I decided to connect a =
large 175uh inductor from the antenna
connection point on the weather proof box to the isolated ground rod. I =
know this inductor is probably over kill in
terms of value but it was in the junk box and waiting for a use for the =
last 25years!! It is wound on a 1.5inch black
plastic water pipe ...about 18ga enamelled wire.
When I connected this inductor the freq at which I see the lowest SWR =
increased up to about 1.830khz which is not
a problem. The surprise is that the noise again seemed to be impacted =
downwards. I am not sure if I am=20
imaging this or whether it is really happening.!!! On Sunday 0330 to =
0430 there was a great opening into EU
with many strong signals and the band noise was really the lowest I have =
ever heard in all my years listening to 160M.
73 Frank VO1HP
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