[cma-l] Community Radio on AM

[Two Lochs Radio]

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!

The Canadian CRC's LRCOV online propagation calculator covers 20 MHz to 40 GHz‎ 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.

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.

Alex


(----- Original Message ----- 
  From: Ian Hickling 
  To: Martin Steers ; The Community Media AssociationDiscussion List 
  Sent: Tuesday, September 23, 2014 4:02 PM
  Subject: [cma-l] Community Radio on AM


  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.
  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.
  I'm sure other members will  have first-hand information.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.commedia.org.uk/pipermail/cma-l/attachments/20140924/cd96987e/attachment.html>