From: NAME: Andy Burns
FUNC: Research and Development
TEL: 0324 493981 <BURNS,AL@A1@GRRD04>
To: "cq-contest@tgv.com"@rcwi01@mrgate@grrd04
Steve, N2IC/0 asked about phased delta loops for 80M.
My primary 40M antenna is a 2 el Quad array, vertically polarized with
1/4 wave spacing using the Collins hybrid coupler system as described in
ON4UN's bible. Switchable to East or West. When I put it together I
measured mutual impedance by opening the loop and shorting one end to the
ground system of my inverted L for 160M. Follow the procedure in the book
to check out each loop.
My advice however if you've got the room is to widen your spacing to 1/4
wave which is a lot less sensitive to inbalance in the resonance of the
loops. The collins method (90 degree phase lag) is very easy to implement
and gives very good performance. In practice, I ended up putting a
phasing stub on the west loop and by changing the shorting bar (hence
changing the loop length) I was able to tune for either maximum gain or
maximum front to back. With the Collins system this seems to work well as
inbalance between the loops doesn't seem to mess the phasing system
up....I think!!
Performance wise, it works great. Came 8th World in 92 ARRL DX 40M single
band behind ON4UN, CT1BOP and the late G3FXB (what a line up.....great
choice of operating strategy....went back to all band for this year!). It
seems to have a good beamwidth (60 degrees) without noticable degradation
of received signal (in comparison with a dipole at 50 ft). 6 S units of
rejection of close in signals from the side. Usually 1-2 S units better
in the forward direction to East Coast or Mid West than the dipole. For a
few bits a wire its not a bad way to get 100+ per hour to the US on 40M
split. I'm sure 80M would be no different. I just wish I had the trees to
hang one in.
Andy
GM0ECO
burns_al@grrd04.dnet.bp.com
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