Topband: Unidirectional Receiving loop

[Earl W Cunningham]

I was just playing around in EZNEC with Pennant designs and thought it
would be interesting to see what I could come up with for a design for a
rotatable small receiving loop that would be unidirectional.

I chose to use a four-sided loop (like a quad loop in the "diamond"
configuration), and arbitrarily chose each side of the loop to be 5 feet
long.  7.07 feet from a corner to the opposite corner seemed to be
reasonably small enough  to even be hand-held.  The wire size I used in
the model is #14 AWG.

The results are encouraging.  With the feedpoint in one corner and a
termination resistor in the opposite corner, better than 30 dB F/B could
be obtained at 1.830 MHz.  The best termination resistor value was ~650
ohms.  The azimuth pattern is cardioid-shaped, with maximum gain off of
the feedpoint end of the loop.  The gain of the antenna on 160m is about
-55 dBi, so a beefy preamp at the receiver would be desireable.

The feedpoint impedace is about 650 ohms, so a Pennant/Flag type of
transformer with a primary/secondary turns ratio of 1 to 3.6 would be
needed to match 50-ohm coax.

If anyone tries this antenna, I would appreciate getting reports on its
performance.

73, de Earl, K6SE