On Mon, 8 Dec 2003 15:29:59 +0000 (UTC), "Reg Edwards"
wrote:

[snip]

Hi Reg,

It so happens the uniformly distributed radiation resistance is exactly
twice the radiation resistance of a 1/2-wave dipole when concentrated at its
centre. So the uniformly distributed radiation resistance along a 1/2-wave
dipole is about 140 ohms. It cannot be measured. It can be calculated from
aerial dimensions. But best just to remember the approximate number 140. It
does depend to small extent on wire diameter and 'end-effect'.

It's annoying, because the tx output Z I'm trying to match is (by a
strange coincidence) 140 ohms! So a folded dipole would be ideal, I
guess. However - and it's a big *however* - I can't use one. I'm stuck
with a telescopic whip and a ground plane the size of a box of Swan
Vestas. I imagine the radiation resistance of such a non-ideal antenna
is pretty low, but until someone can gimme a ballpark figure for it, I
can't even begin to think about how to go about matching it. :-(


--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill