Questions: Does anybody know how to calculate/estimate/measure the
efficiency of our wire antenna to determine our ERP power?
Does anybody know of previous OE activities on 136kHz or is ours the
very first OE-DL contact as some of our QSO partners say?
The antenna is rather unusual but if you look at it as a 'Marconi' then you
should have an almost infinite topload (compared to the 13m vertical section).
The radiation resistance of a short vertical monopole with infinite topload is
Ra = 160 x (Pi * l/L)^2
where Ra = radiation resistance, Pi = 3.1415... , l = antenna height, L =
wavelength and ^2 = squared.
So as a 'wild guess' I would estimate Ra as 0.055 Ohms (55 milliOhms).
Your ERP further depends on the antennacurrent (Ia) : ERP = Ra x Ia^2
73, Rik ON7YD
Rik Strobbe ON7YD
[email protected]
Villadreef 14 B-3128 Baal BELGIUM (JO20IX)
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