---------- Forwarded message ----------
From: "Joe Subich, W4TV" <lists@subich.com>
To: "'Ross Primrose'" <aj4ll@aiko.com>, <herbs@surfvi.com>
Date: Mon, 15 Jun 2009 23:04:27 -0400
Subject: RE: Topband: Twin Lead Marconi Antenna
AJ4LL wrote:
> > I do recall however that the theory that the ground losses were
> > reduced by a 4 to 1 base impedance multiplication factor has been
> > disputed.
>
> Citation? That's still the working theory in Low Band DXing.
Citation? Try: http://www.w8ji.com/radiation_resistance.htm
Tom quite clearly shows that the 4:1 step up in the feedpoint
impedance does not change the current flowing in the ground.
Since neither the current in the ground, nor the current being
radiated change one iota due to the change in ratio of current
to voltage in the feedline (at the feedpoint), there is NO
CHANGE in ground losses and/or antenna efficiency.
The only benefit of a folded monopole - particularly the large
diameter versions used in broadcast service - is a more easily
matched feedpoint and perhaps slightly greater bandwidth due
to the greater diameter of the structure (smaller L/D ratio).
73,
... Joe, W4TV
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|