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<DIV><FONT size=2 face=Tahoma>The only Ofcom community AM coverage plot I have
happened to look at in the past simply drew a nominal 5km radius circle -
despite it being over a hilly city with a river through it!
<DIV><FONT size=2 face=Tahoma><SPAN class=st></SPAN></FONT> </DIV>The
Canadian CRC's LRCOV online propagation calculator covers 20 MHz to 40 GHz
<SPAN class=st>using the standard Longley Rice propagation model, but as you say
analyzing the antenna propagation pattern is a prerequisite for sensible
results. The standard NEC tools will cover the AM frequencies quite happily, but
at such long wavelengths the effects of ground proximity and
nature and nearby metalwork/support guys make it a fairly
uncertain process unless you are dealing with high wires in large open fields as
used by the major broadcasters.</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Tahoma><SPAN class=st></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Tahoma><SPAN class=st>Also AM propagation varies
dramatically between day and night, though this is generally of concern only to
wide area broadcasters, not community stations received from the surface
wave unless they are interfered with at night by a far distant sky
wave.</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Tahoma><SPAN class=st><BR></SPAN></FONT><FONT size=2
face=Tahoma><SPAN class=st>Alex</SPAN></FONT></DIV>
<DIV><FONT size=2 face=Tahoma><SPAN class=st></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Tahoma><SPAN class=st></SPAN></FONT> </DIV>
<DIV><FONT size=2 face=Tahoma><SPAN class=st>(</SPAN></FONT>----- Original
Message ----- </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=transplanfm@hotmail.com href="mailto:transplanfm@hotmail.com">Ian
Hickling</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=martin@martinsteers.co.uk
href="mailto:martin@martinsteers.co.uk">Martin Steers</A> ; <A
title=cma-l@mailman.commedia.org.uk
href="mailto:cma-l@mailman.commedia.org.uk">The Community Media
AssociationDiscussion List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, September 23, 2014 4:02
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [cma-l] Community Radio on
AM</DIV>
<DIV><BR></DIV>
<DIV dir=ltr>I haven't done any real appraisals apart for the Farnborough
station which manages about a 2-mile radius in daytime hours which is be
barely adequate but does at least cover the core population.
<DIV>I'm not aware of any computer coverage software that will cope with MF -
and of course there's the question of exactly the EMRP value - and even more
indeterminate - the antenna propagation pattern.<BR>I'm sure other members
will have first-hand
information.<BR></DIV></DIV></BLOCKQUOTE></BODY></HTML>