[TowerTalk] Feeding a Grounded Vertical Monopole

[Roger Parsons]

The obvious way to feed a grounded vertical monopole would seem to be a gamma match. However, in my particular circumstance I am not able to adjust the gamma length and the 'rod' must be a single wire.

It has seemed to me that feeding the antenna this way should still be possible, but that it would be most unlikely for the feed impedance to be made 50 Ohms resistive using a gamma or omega match, and that a more complex matching network would be necessary.

However, more cogitation has revealed that not all matching geometries are equal:

If the gamma rod has zero length, then no power can be fed to the antenna;

If the gamma rod is the same length as a quarter wave radiator, then the antenna becomes a folded vertical;

If the radiator and the gamma rod are identical, but the antenna is a half wave long, then it degenerates into a transmission line shorted at the far end and can accept no power. (This is true for any half wave multiple of a folded monopole.)

Soooo.....

Is it true that if losses are ignored and a match can be obtained the antenna will radiate all the power fed to it? And that if the antenna approaches one of the situations above, that the match may become extremely difficult but still possible in principle?

I think these two propositions are correct, but thoughts would be appreciated.

73 Roger
VE3ZI