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From: hajo.brandt.dj1zb@t-online.de
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 <1K7Y7g-1RYRXM0@fwd31.t-online.de> 
 <20080617131417.C7BE4F3863@smtps02.kuleuven.be>
In-Reply-To:<20080617131417.C7BE4F3863@smtps02.kuleuven.be>
To:  <rsgb_lf_group@blacksheep.org>
Date: 17 Jun 2008 22:51 GMT
Message-ID: <1K8k27-03I2I00@fwd24.t-online.de>
Subject: Re: LF: Finbar's Compact 500kHz Vertical
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Dear Rik,

thank You for your contribution. Especially your last sentence is
interesting for me because this may explain the success of MF-stations
operating close to the coast.

Another example for exceptionally high antennas on MF for me is DI2AM,
located on a museum ship in the harbour of Rostock. I have been informed
that the antenna has been put up between two masts of 30 meter in
height. Other favourable conditions are the low ground loss onboard of a
ship and also the vicinity of water, of course.  

In general I do not have any objections to Finbar's setup; it shows that
effective MF antennas can be built up on a rather small area. 

But I am not yet convinced that height of MF antennas should not matter,
and I will continue to observe the scenery.

OK?

73 Ha-Jo, DJ1ZB


  "Rik Strobbe" <rik.strobbe@fys.kuleuven.be> schrieb: 
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

Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm for more
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<body   link="#000000" vlink="#000000" alink="#000080" topmargin=0  leftmargin=0 marginwidth="0" marginheight="0"><font face="Times New  Roman" size=3 color=#000000><FONT   face="Arial Black"><FONT size=2>Dear Rik,<BR><BR>thank You for your 
contribution. Especially your last sentence is interesting for me
because this 
may explain the success of MF-stations operating close to the 
coast.<BR><BR>Another example for exceptionally high antennas on MF for
me is 
DI2AM, located on a museum ship in the harbour of Rostock. I have been
informed 
that the antenna has been put up between&nbsp;two masts of 30 meter in
height. 
Other favourable conditions are the low ground loss onboard of a ship
and also 
the vicinity of water, of course.&nbsp;&nbsp;<BR><BR>In general I do not
have 
any objections to Finbar's setup; it shows that effective MF antennas
can be 
built&nbsp;up on a rather small area.&nbsp;<BR><BR>But I am not yet
convinced 
that height of MF antennas should not matter, and I will continue to
observe the 
scenery.<BR><BR>OK?<BR><BR>73 Ha-Jo, 
DJ1ZB<BR></FONT><BR><BR></FONT>&nbsp;</font>
"Rik Strobbe" &lt;rik.strobbe@fys.kuleuven.be&gt; schrieb:
<blockquote style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT:  5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

<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>
<BR>
<FONT FACE='3D"Arial"' SIZE=3>Disclaimer: <A HREF=   "http://www.kuleuven.be/cwis/email_disclaimer.htm">http://www.kuleuven.be/cwis/email_disclaimer.htm</A>
for more information.</FONT>
<BR>
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