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<div class="moz-cite-prefix">I've dusted off an old spreadsheet if
anyone wants a copy. It's based on the mf radio prop maths, don't
ask me, I think it has some fiddle factors in it from memory. The
file was pre excel Supercalc etc., and as I now use Linux it's
been re-saved as excel .xls from gnumeric. You just change the
power box value and reload it to get the field strength figures.
I think it also produced graphs. The frequency is set at 1 meg, I
have versions for the high end and low end but it's probably not
that accurate. <br>
<br>
I don't think this mail list accepts attachments so you'll have to
email me direct.<br>
<br>
Regards, Tony Bailey<br>
<br>
On 24/09/14 15:19, Alan Coote wrote:<br>
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<p class="MsoNormal"><a moz-do-not-send="true"
name="_MailEndCompose"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I’m
going back a bit, but I recall Longley Rice only being
useful for VHF between 70Mhz - 250MHz. Either side, other
models need to kick in. I also remember there being a lot
of fudge factors.<o:p></o:p></span></a></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Anything
that is line of sight you could always use; Free Space Loss
= 20log(d km) +20log(f MHz) +32.4. Then subtract a bit for
buildings and trees, and a bit if the signal path is over
water or damp ground, subtract a bit more for cabling and
connectors and then multiply by the antenna gain… or just
use software to do it for you! <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The
above is useless for AM band propagation of course. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Kind
Regards</span><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Alan<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><a moz-do-not-send="true"
href="http://www.letstalkbusinessonline.com/"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif"">Hear
Alan Every Week on Let’s Talk Business The UK’s Premier
Radio Programme For Current and Future Entrepreneurs -
Now Broadcast To 4.3 Million People </span></a><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Email
- </span><a moz-do-not-send="true"
href="mailto:alan.coote@5digital.co.uk"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif"">alan.coote@5digital.co.uk</span></a><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Phone
- 0800 949 6655<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Mobile
- 07801 518858<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Twitter
- </span><a moz-do-not-send="true"
href="http://www.twitter.com/TheAlanCoote"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif"">@TheAlanCoote</span></a><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Web
- </span><a moz-do-not-send="true"
href="http://www.5digital.co.uk/"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif"">http://www.5digital.co.uk</span></a><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><img
id="Picture_x0020_2"
src="cid:part6.09070804.00080007@pilgrimsound.co.uk"
alt="cid:image001.gif@01CE03CD.223AC920" border="0"
height="71" width="200"><o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The
Media Production, Broadcasting and Training Company<o:p></o:p></span></p>
</div>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""
lang="EN-US"> <a class="moz-txt-link-abbreviated" href="mailto:cma-l-bounces@mailman.commedia.org.uk">cma-l-bounces@mailman.commedia.org.uk</a>
[<a class="moz-txt-link-freetext" href="mailto:cma-l-bounces@mailman.commedia.org.uk">mailto:cma-l-bounces@mailman.commedia.org.uk</a>] <b>On
Behalf Of </b>Two Lochs Radio<br>
<b>Sent:</b> 24 September 2014 11:32<br>
<b>To:</b> The Community Media Association Discussion
List; Martin Steers<br>
<b>Cc:</b> Ian Hickling<br>
<b>Subject:</b> Re: [cma-l] Community Radio on AM<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">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! <o:p></o:p></span></p>
<div>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <o:p></o:p></span></p>
</div>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">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></span><span
style="font-family:"Calibri","sans-serif""><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span class="st"><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">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></span><span
style="font-family:"Calibri","sans-serif""><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif""><br>
<span class="st">Alex</span></span><span
style="font-family:"Calibri","sans-serif""><o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span class="st"><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">(</span></span><span
style="font-family:"Calibri","sans-serif"">-----
Original Message ----- <o:p></o:p></span></p>
</div>
<blockquote style="border:none;border-left:solid black
1.5pt;padding:0cm 0cm 0cm
4.0pt;margin-left:3.75pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt">
<div>
<p class="MsoNormal" style="background:#E4E4E4"><b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">From:</span></b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">
<a moz-do-not-send="true"
href="mailto:transplanfm@hotmail.com"
title="transplanfm@hotmail.com">Ian Hickling</a> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">To:</span></b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">
<a moz-do-not-send="true"
href="mailto:martin@martinsteers.co.uk"
title="martin@martinsteers.co.uk">Martin Steers</a> ;
<a moz-do-not-send="true"
href="mailto:cma-l@mailman.commedia.org.uk"
title="cma-l@mailman.commedia.org.uk">The Community
Media AssociationDiscussion List</a> <o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Sent:</span></b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">
Tuesday, September 23, 2014 4:02 PM<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">Subject:</span></b><span
style="font-size:10.0pt;font-family:"Arial","sans-serif"">
[cma-l] Community Radio on AM<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif""><o:p> </o:p></span></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">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. <o:p></o:p></span></p>
<div>
<p class="MsoNormal"><span
style="font-family:"Calibri","sans-serif"">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.<o:p></o:p></span></p>
</div>
</div>
</blockquote>
</div>
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