Hi, Giulio and Group.
On Mon, 26 Aug 2002, Giulio Scaroni wrote:
Hi Alex and all,
soon i'll measure exactly the antenna current, but one things that appear
in this discussion, is that the antenna work very well, it is only a single
wire 60 meters long about 1 meters far at the top of the tower, and about
25 meters far at the base.
I have read that wire near a tower has many losses, but this seems to
confirm the opposite, also the tower that i use in winter in Mantova have
the same wire antenna, little bit longer, and with only 100 W my signal is
perfectly audible in UK...
So, may be that the big tower act like a big additional vertical capacitance
to increase signal output??
I think in such a configuration tower act as radiated part of antenna
also. It makes not simple to estimate EPR in this case "by a pencil". But
if use someone version of NEC program (EZNEC, ELNEC, MMANA, MININEC
e t.c.) it is posible. But antenna currend is need if use program also.
Such a program can not correctly estimate loss resistance. So its "direct"
using is imposible on LF. But if set souce off current type with measured
(experimental) current then EPR, imagine part of input impedance
(ractance) and field strenght should be aproximatly correct, only TX power
and real part or input impedance will be incorrect. But TX power, is
known with out any calculation! Such a combination of experiment and
modeling sould give reasonable estimation of EPR in such a complex
condition. Of cose tower should be incloud in NEC model also.
But any way antenna current is need...
73 de RA9MB/Alex
http://www.qsl.net/ra9mb
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