I think Ed has some good advice.
Although this was for VHF the concept, already mentioned is applicable
to mot any band and/or mode.
The wide area repeater was located in my garage. The antenna
(Shakespeare commercial) was on top of the 90 ft tower behind the garage.
The tower had a tribander on it as well and was guyed with a small EHS
(Don't remember the size, bit IIRC it was less than a quarter in, so
probably 3/16ths.
The guys were broken up with large insulators. The bottom ends had an
insulator, maybe 5' or more from the anchor. That was 30 years ago, so
recollections are a bit hazy<:-)
I discovered that rubbing an 8 or 10" screwdriver on the guy above the
bottom insulator would completely wipe out a 50W mobile only 2 or so
miles distant.
So, "I think" somewhere in the system was a poor connection (shield to
ground? Didn't even need to be on that bad, something in the wire
antennas, or tribander) I did discover (later on) the SWR on a simple
3L tribander that used a fiber center insulator, with 1/4" SS screws
into each side of the DE for a direct feed. No balun or matching
network. One side was no longer making contact. That leaves me guessing
that connection was probably the source of the de-sence.
Even old fences are notorious for rectification when located near the
antennas
All our fences are plastic as the don't keep anything in, or out.
A garden is impossible as we have woods on two sides of the yard and the
critters get the vegetables before we do. Our neighbors gave up too.
The neighbors still connected TV antenna pre-amp in the attic with no AB
switch is now rare with cable and satellite, but there are cases where
someone has left an outside TV antenna connected to the TV set along
with the other service.
73
Roger (K8RI)
On 9/28/2016 Wednesday 8:54 AM, Ed Sawyer wrote:
I would advocate "going clean" on the worst offender scenario and have pure
coax going from the amp to the antenna. Same on the receive circuit and see
if it goes away. You might hear a clean harmonic now but does the broadband
noise go away. If it doesn't, you have just eliminated a SLEW of
possibilities. If it does, add things back one at a time and observe.
This has worked for me.
By the way, I don't need stubs - I have found out. Just Bandpass filters
and antenna separation. 1.5kW on all bands and SO2R.
Ed N1UR
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73
Roger (K8RI)
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