Date: Tue, 17 Jun 2008 15:19:35 +0200
To: rsgb_lf_group@blacksheep.org
From: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
In-Reply-To: <1K7Y7g-1RYRXM0@fwd31.t-online.de>
References: <57a24ca70806131827p690673d0kb0b8c0d76d85fddc@mail.gmail.com>
 <1K7Y7g-1RYRXM0@fwd31.t-online.de>
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Subject: Re: LF: Finbar's Compact 500kHz Vertical
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Dear HaJo,

>But in general I feel that antenna height should not be disregarded. 
>Even with equal ERP sky waves may develop better from higher aerials.
>
>HW?

I guess that the only cause that 2 antennas fed with the same ERP 
produce different signals is a difference in the (vertical) radiation 
pattern, ie. the takeoff angle.
I simulated a 30m, 10m and 3m vertical (at 502kHz) with mmana_gal and 
found only very small differences: from 18.2 degrees for the 30m 
vertical to 18.6 degrees for the 3m vertical. This for a uniform 
ground with a conductivity of 10mS/m.
Making the ground poor (1mS/m) results in a takeoff angle of about 26 
degrees (+/- a few tenths depending on the height).
Increasing the conductivity to 100mS/m reduces the takeoff angle to 
12-13 degrees.

73, Rik  ON7YD - OR7T 

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<font face="Courier New, Courier">Dear HaJo,<br><br>
<blockquote type=cite class=cite cite="">But in general I feel that
antenna height should not be disregarded. Even with equal ERP sky waves
may develop better from higher aerials.<br><br>
HW?</blockquote><br>
I guess that the only cause that 2 antennas fed with the same ERP produce
different signals is a difference in the (vertical) radiation pattern,
ie. the takeoff angle.<br>
I simulated a 30m, 10m and 3m vertical (at 502kHz) with mmana_gal and
found only very small differences: from 18.2 degrees for the 30m vertical
to 18.6 degrees for the 3m vertical. This for a uniform ground with a
conductivity of 10mS/m.<br>
Making the ground poor (1mS/m) results in a takeoff angle of about 26
degrees (+/- a few tenths depending on the height).<br>
Increasing the conductivity to 100mS/m reduces the takeoff angle to 12-13
degrees.<br><br>
73, Rik&nbsp; ON7YD - OR7T</font><BR>
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<FONT FACE=3D"Arial" SIZE=3D2>Disclaimer: <A HREF=  "http://www.kuleuven.be/cwis/email_disclaimer.htm">http://www.kuleuven.be/cwis/email_disclaimer.htm</A> for more information.</FONT>
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