TopBand: Antenna separation

[Paul and Abbi Elliott]

I can't comment directly about beverage and transmitting antenna
interaction, but I have made observations about antenna interactions on my
urban antenna "garden" that is 120'x120'.  My transmitting antenna is a
bent piece of wire that goes upward from the ground at an angle of about 60
degrees  above the horizontal to a maximum height of 52', then slants back
towards the ground--included angle between the two segments is about 110
degrees, and the far end is about 12' above the ground.  The ground system
consists of buried radials, probably about 40 in number and ranging in
length from 15' to 100', restricted essentially to one quadrant (except for
the few tht I was able to sneak into the alley behind the house).  By trial
and error I made the total length such that, with an appropriate series
capacitor (about 170 pf), I get an swr of 1:1 at 1830 mhz.  2:1 swr
bandwith is from 1805 to 1855 mhz (approximately).  Some of you that are
good at modeling want to tell me how bad my ground system is?

My receiving antennas consist of three 8' diameter and one 12' diameter
shielded tuned loops--plus one coax bazooka type.  If I do not open, with a
relay, the fed end of the transmitting antenna while receiving, both the
directivity patterns and S/N ratio of the receiving antennas are grossly
degraded.

With a Radio Shack portable receiver, tuned to 1830 mhz and in the CW mode,
held about a foot away from the transmitting antenna, the difference in
noise picked up by receiver when the fed end of antenna is (a) open or (b)
connected to the feed system amazed me the first time I tried it.  With the
relay open and noise barely audible, the noise became a loud roar when the
relay was closed.  The difference in noise reradiated by my transmitting
antenna is significant in the two configurations.

73 Paul W5DM

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