Tad Danley wrote:
I have started to experiment with EZNEC and am modeling a couple of loop
antennas including some delta loops. I see references to hams using 4:1
baluns with these antennas, but the models I see show a feed point
impedance of roughly 100 ohms. I'm not sure how a 4:1 balun would help
- what am I missing?

The resonant feedpoint of the 80m loop that I modeled
with EZNEC is 115 ohms. Without a 4:1 at the feedpoint,
the 50 ohm SWR is 2.3:1 inviting foldback. With a 4:1
balun, the 50 ohm SWR is 1.7:1 with no foldback. It is
rare for the feedpoint resistance of a loop to be exactly
100 ohms.

Of course, if the loop is fed with high-Z0 ladder-line,
the 100 ohm feedpoint resistance is transformed to a higher
impedance value where a 4:1 balun might be more effective.

For single-band operation, most hams simply feed the loop
with 1/4WL of Z0=75 ohm coax (quarter-wave transformer).
--
73, Cecil http://www.w5dxp.com