[Lowfer] UWL on

[Garry Hess]

Eric, as others have mentioned, an antenna capacitance of only 5 pf is 
way too low. But that's not what you have. At 185.3 kHz, 6.9 mH 
inductance resonates with 107 pf. Confirm that by solving 
C=1/[L*(2*pi*f)^2], where C is in Farads, L is in Henry, and f is in Hz. 
107 pf is still pretty low, and why the inductance is so high (and 
therefore lossier than it might be). My 35' mast has a double tophat 
that measures 376 pf and needs 1.96 mH to resonate at the watering hole. 
The ground system is lousy though so there's plenty of room for improvement.

Incidentally, as I mentioned some time ago, I tried to measure the 
effective C presented by the antenna with an LC meter. It gave wildly 
changing numbers. I then built a Wheatstone bridge so I could measure R 
as well as C. That didn't work either. In fact, I couldn't even read the 
bleeder resistor with any of the 3 DVMs I tried. Putting a scope on the 
open-circuit antenna feed showed why - there was a 100 V peak-peak swing 
of a pseudo-sine wave related to 60 Hz. Since the power lines were at 
least 100' away that wasn't expected. Eventually resonance was found by 
using a high-powered signal generator and SWR bridge.

73, Garry, K3SIW, EN52ta, Elgin, IL