On Sun, 9 Jan 2005, dj9dw wrote:

Alexander,
how much topload on your vertical?
Mine is 22m high with 300pF top. R at feedpoint is 24 Ohm. After some tests
(compared with DCF39) and calculations the radiating restistance seems to be
abt. 45 mOhm. Realistic?

Seems should be bit grater. For infinity large top load
1600(22/2200)^=0.16=160 mOhm. Capacitance of vertical wire aproximaly
6*22=130 pF wich is less then 300pF. Certanly top load is not infinite
in comparison with 130 pF. Antenna effective height is reduced by factor
[Ct/(Ct+Cv)+1]/2 where Ct is capacitance of top load Cv is capacitance of
vertical wire. Thus Heff=22[300/430+1]/2=18.7m R=1600(18.7/2200)^2=0.12
Ohm=120 mOhm.

Thus effectivety is 0.12/24=0.005 or 0.5 percent. To radiate 1W one need
TX of 200W.

Certanly all of this is true only if top load is absolutely horizontal.
If free end goes doun then resistance should be less then 120 mOhm.
Besides reradiation by enviroment can reduce radiated power.

73 de RA9MB/Alex
http://www.qsl.net/ra9mb