Having trouble responding to the above posting. Hope it is not duplicating
what I have tried to send before.

The nominal impedance of a 40 m dipole on 20 m, at 30 ft above an average
ground, is
4700 + j0. There may be some inductive or capacitive reactance present --
depending on the exact length of the antenna -- but it will not effect the
transmission line losses significantly.

100 ft of RG 58 exhibits a total line loss of about 13 dB when terminated
with the above impedance. i.e. 100 W in gives 5 W radiated.

For the above analysis I used NEC 2 for the antenna model, and ARRL's TLA
for the transmission line loss.

The results are very similar to K6MHE, but should show zero reactance on
some frequency. Anyway the losses are close.

Regards,

Frank