"Frank's" wrote in message
news:3z0Mf.1838$dg.1085@clgrps13...

"John, N9JG" wrote in message
news:ij%Lf.797528$_o.574035@attbi_s71...
Most people put the series tuning capacitor in the top side and the feed
point at the bottom side. Since the capacitor, motor, and their mounting
hardware is quite heavy, I am currently planning to do the reverse of the
above, i.e., tuning capacitor at bottom and feed point at the top. It is
not clear to me if there is any difference between these two
configurations.

John, N9JG

I have not attempted to model the gamma match, but doubt it will change
the current distribution. Feeding at the top places the minimum current
at the loop base which seems to effect the high angle radiation only. The
gain straight up is about + 2 dBi, and -3 dBi when reversed. Low angle
radiation, for example at 10 deg elevation, is - 3 dBi in both cases.
Removing the capacitor totally reverses the current distribution. Maximum
gain occurs parallel to the loop plane.

Frank, VE6CB

Also top feed increases the input impedance to 2.664 - j0.949, with the
capacitive load 0.1 -j858 at 3.75 MHz. (NEC 4.1 double precision).