Hello All:
I have been reading postings here on Towertalk for a year or so &
have not posted anything till now. This one has me concerned and I
wonder if anyone has experienced a similar problem. This is
occurring at N3RS. I am posting this for Sig, since he is not on this
reflector.
He has two towers, spaced about 125 ft, that run along a 35 degree
bearing line with a 3-stack of 5 el 20M yagis, a 3-stack of 4 el 15M
yagis, and a rotary 80M dipole on one tower and a 40M 3 el yagi
and 3-stack of 5 el 10M yagis on the second.
The 20M yagis are mounted on TIC rings and two of the 15M yagis
are mounted using IIX side-arms. The top 15M yagi and the 80M
dipole are stacked 10 ft apart on the mast at the top of the tower.
Each antenna in the stack can be positioned independently. This
tower is 130 ft tall, and the 20M yagis are at 37/77/117 ft levels and
the 15M yagis are at 46/87/130 ft levels. The 80M EF-180C is
mounted at 140 ft.
The second tower has the 3 el 40M yagi at 140 ft and the 10M yagis
are at 83/50/22 ft levels. The 40M yagi & the top 10M yagi rotate
independently and the bottom two 10M yagis rotate together on a
mast that runs along side of one of the tower legs.
Here is the problem: When we aim the 40M yagi at the 20/15/80
meter tower and key the rig at any power level I experience
broadband (covers the entire 20M and 15M bands) noise. At
100W, the noise is tolerable, but at 1500W it is S-9 on both bands,
providing the 20M antennas are pointed at Europe (roughly 45
degrees). If the antennas are rotated, no mater where they are
pointing, the noise is there. The noise disappears when the 20M
antennas are pointed to Asia or to the South.
It appears that some form of non-linear conduction is occurring in
the rotation mechanism and generating the RFI. I have considered
using some sort of conductive grease on the gears of the rings, but
wanted to know if anyone else has experienced this sort of problem
& solved it first.
Where could Sig buy some conductive grease, if this is a potential
solution?
Any ideas? We need help!
Tom, N2SR
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