[cma-l] Community Radio on AM

Thu Sep 25 08:23:05 BST 2014

I don't agree that ".....proper computerised tools are needed to do it properly" Glyn - sorry.Computerised tools have got us into the farce that we are currently in.Certainly we need proper planning - but after that we need practical onsite trials as you say with measurement and analysis.This however is costly in terms of the equipment and manpower which Ofcom does not have available and is not going to get funded by HMG.So Ofcom could do it but won't.
Lots of us can do it - but Ofcom doesn't accept that concept.

From: tlr at gairloch.co.uk
To: info at a-bc.co.uk
Date: Wed, 24 Sep 2014 18:11:01 +0100
CC: cma-l at mailman.commedia.org.uk
Subject: Re: [cma-l] Community Radio on AM

I understand the 'complex scientific' side of it, 
but I still don't honestly see how the map helps give any insight other than in 
the crudest measure of overall density of stations. 

It shows the general density of stations and is a 
nice tool for browsing stations and frequencies, but it gives no visual 
representation whatever of frequencies or powers, so I don't honestly see how it 
gives even the vaguest insight into the interference landscape for a 
station.

It could maybe take useful steps in 
that direction with some development. For example if one could select a 
frequency or transmitter of interest and set a filter to show only stations of 
that frequency, or of that frequency plus adjacent and/or image channels it 
would start to give an idea of potential for interference. Combined with perhaps 
a crude free space range indication using semi-transparent overlays based 
on on powers and direction templayes it might beging to give a rough feel for 
the interference landscape for a given station. But as it stands I don't see how 
it does that in the slightest.

Not meaning to be picky, honest - I like it 
for what it is, and it does give a feel for the geographic distribution of CR 
stations, but it doesn't seem to me to offer any useful insight or even 
vague feel for the interference landscape.

Alex

  ----- Original Message ----- 
  From: 
  Associated Broadcast 
  Consultants 
  To: Two Lochs Radio 
  Cc: The Community Media Association 
  Discussion List 
  Sent: Wednesday, September 24, 2014 5:37 
  PM
  Subject: Re: [cma-l] Community Radio on 
  AM

  Absolutely right Alex - the frequency selective map would only be 
  for getting an "insight" or feel for the interference landscape - proper 
  computerised tools are needed to do it properly.

  It's complex and scientific, but this post below gives a pictorial, 
  non-technical insight into the "Protection Ratios" that Ofcom use, and are one 
  of the reasons they often say there are no frequencies available:-

  http://a-bc.co.uk/ofcom-fmvhf-protection-ratios-illustrated/

  Glyn

  -- 
Glyn Roylance - Principal Consultant
  Associated Broadcast 
  Consultants

  On 24 September 2014 16:58, Two Lochs Radio <tlr at gairloch.co.uk> wrote:

    Hi Glynn

    That's a nice map for browsing, but as far as 
    mapping all transmitters to allow assessment of potential 
    interference, it surely isn't the way to go. As you'll be well aware 
    you need much more than a simple mapping of potential co-channels - you 
    have to take into account image channels and the directional power templates 
    of antennas at the very least, even before thinking about the intervening 
    terrain.  You also have to take into account transmissions in 
    neighbouring countries of course.

    I think all that can be done far more effectively in 
    tabular form than on a map.

    Of course, the elephant in this particular 
    room is not in any case what frequencies are or aren't 
    occupied, but what parameters Ofcom applies in assessing their 
    potential for mutual interference - eg should a 99% confidence level or a 
    90% confidence level be used, should second adjacent channel be regarded as 
    safe or not? Those are what make all the difference to the assumed 
    potential for interference between transmitters. Similarly, is potential 
    interference acceptable for 0.1% or 1% of the time or location? All these 
    parameters are really what set the technical bar as to whether or not 
    there are channels available.  Then of course there are strategic and 
    political issues, agrements for the BBC to have priority use of certain 
    sub-bands etc.

    One thing that could be considered for releasing 
    more community radio frequencies is for Ofcom to reuse channels more 
    closely on the basis of a mutual agreement between stations that they 
    will not complain about the remote possibility of mutual interference less 
    than say 1% of the time in 10% of their fringe. We have transmitters on the 
    same frequencies just a few miles apart, but terrain-limited with no 
    significant mutual interference in locations of interest, because we were 
    able to agree not to complain about our transmitters interfering with each 
    other! A similar thing happens on 96.6 between Nevis Radio (Fort 
    William) and MFR (Aviemore) in the Laggan area half way between 
    them. I suspect many groups would be willing to accept a service that might 
    be subject to a little marginal interference in some limited locations 
    rather thna no licence at all.

    As for suggestions on the map, which is nonetheless 
    nice to have, could I suggest you add in the Scottish not-for-profit 
    stations that operate as non-profit community stations, but for 
    historical reasons have commercial licences (Cuillin FM, Two Lochs Radio, 
    Lochbroom FM, Argyll FM, Oban FM, Isles FM). That would give a more 
    representative picture of community radio cover in the northwest of the UK, 
    which otherwise looks a bit empty on the map! There are also community 
    op-outs from MFR in the north-east.

    Also for adding the Northern Ireland stations there 
    is a batch convertor for Irish grid references here http://www.osi.ie/calculators/batch.asp?alias=/services/gps-services/co-ordinate-converter

    Alex

    ----- Original Message ----- 

      From: 
      Associated Broadcast Consultants 
      To: The Community 
      Media Association Discussion List 
      Sent: Wednesday, September 24, 2014 
      2:54 PM
      Subject: Re: [cma-l] Community Radio 
      on AM

      Further to Ian's update below - we recently mapped the Ofcom 
      data for FM CR's onto an interactive Google Map that you can browse, zoom 
      etc.  If you click on any site if gives the essential information. 

      http://a-bc.co.uk/community-radio-station-map/

      If there is interest we might do a similar map for all UK 
      transmitters (nearly 2000 of them) that you can filter by frequency - thus 
      to get an insight into co-channel interference for any 
      station/location/frequency you wish.  Or other variations if people 
      have suggestions.

      Regards, Glyn

_______________________________________________

Reply - cma-l at commedia.org.uk

The cma-l mailing list is a members' service provided by the Community Media Association - http://www.commedia.org.uk
Twitter: http://twitter.com/community_media
http://www.facebook.com/CommunityMediaAssociation
Canstream Internet Radio & Video: http://www.canstream.co.uk/
_______________________________________________

Mailing list guidelines: http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/
_______________________________________________

To unsubscribe or manage your CMA-L mailing list subscription please visit:
http://mailman.commedia.org.uk/mailman/listinfo/cma-l 		 	   		  
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.commedia.org.uk/pipermail/cma-l/attachments/20140925/fb1f2199/attachment.html>