Eric,
Being close to the transmit antenna should not be an issue for the KB7GF or
the K9AY, other than damaging the circuitry in the outside unit. For
instance, will the terminating resistors in the K9AY absorb too much power?
They use two watt resistors for the termination matrix and I have seen them
turn black especially the lower values if too much power is in close
proximity. If you are looking at the KB7GF antenna, you might want to find
out if it will damage the preamps if you are that close to the transmit
antenna.
Raising either antenna will improve its performance, though not much unless
you go significantly higher. The KB7GF commercial array has eight
directions and you will likely have a better shot at canceling single source
noises. The K9AY antenna requires a ground stake as it works against ground
and the KB7GF does not since each loop is fully closed. The four square
will be significantly distorted by the proximity of the transmit antenna,
unless one can successfully detune it while in receive. The K9AY will hear
signals of high angle of arrival that a four square will not and vice versa.
I know of a few that have both the four square and a K9AY.
Jim, KR9U
_____________
Date: Sun, 11 Aug 2013 14:24:16 -0400
From: Eric Rosenberg <ericrosenberg.dc@gmail.com>
To: Tower Talk Mailing List <towertalk@contesting.com>
Subject: [TowerTalk] Comparing K9AY Loop and KB7GF Shared Apex Loop
Array?
I'm in need of a decent 160 receive antenna that can fit in my 144 ft
(N-S) x 44 ft (E-W) noisy urban lot. I'm surrounded by (old) power lines and
near a high power AMer (WFED, formerly WTOP) at 1500 kHz. The 160 and 80m
inverted L's and 40m half-square run N-S from the back of the lot to the
front.
I've played with EWE's and Pennants, both of which are rather mediocre.
Generally speaking, the Inv-L's have been better, albeit noisier, receive
antennas.
I've looked at K9AYs and now the KB7GF array, which seem to be quite
similar. I'd like to think I can fit either in my backyard, but if I do,
they will be very close to the TX antennas... *maybe* 20 feet from the
verticals, and certainly underneath all the wires. Is one substantially
better than the other?
A major criteria is that the horizontal sections (wires) have to be 10 feet
above the ground... I don't want to behead anyone walking in the backyard!
Is this all a pipe dream?
Sagely advice is appreciated.
73,
Eric W3DQ
Washington, DC
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