[cma-l] AM community radio
Ian Hickling
transplanfm at hotmail.com
Wed Sep 16 20:20:02 BST 2015
All perfectly acceptable - but as an experienced propagation engineer my concern is that any departure from a vertical end-corrected quarter wave radiator operating on a groundplane of at least .55 wavelength diameter, the energy propagation pattern is uncertain and effectively impossible to either determine or plot.In order to take his order - and his money - I have to give the Client an assurance that he will be able to cover his audience effectively - and that simply isn't possible with a cut-down compensated radiator on a much smaller earth mat.
Ian Hickling
Partner
Office: 01635 578435 (7am-11pm UK time)Carphone: 07530 980115 (only responds when driving)6 Horn Street, Compton, NEWBURY, RG20 6QS
Date: Wed, 16 Sep 2015 08:08:07 +0100
From: ravensound at pilgrimsound.co.uk
To: cma-l at mailman.commedia.org.uk
Subject: Re: [cma-l] AM community radio
Ian et al,
I've only ever used a 1 watt (just about) setup for AM RSLs and
that typically had to be running 15 Watts at the tx output valve.
I've seen bigger amps used but we had various antennas including a
steel telescopic mast, aluminium tube vertical, plastic drainpipes
and a T wire. The latter worked well with a 150 ft counterpoise
earth running about 450 mA aerial current. Reports from more than
50 miles but the effective local coverage was around 3 miles in
practice.
Running my AM spreadsheet calculator it gives for comparison
purposes the 66 dB contour at 2.5 km (1 watt); 5 km (10 watts); 8
km (70 watts). The last two probably equate to tx powers of 150
watts and 1000 watts. I would think it might be worth pointing
this out to prospective licensees as there is clearly a
significant cost/benefit issue here.
Regards, Tony
On 15/09/15 17:10, Ian Hickling wrote:
Phil
I'm not denying at all that AM has its advantages and uses
- and believe me I wasn't being negative - just very
down-to-earth practical
We've run AM RSLs with a guyed 18m pole with a top hat - and
we have one CR running with the £3500 classic Radica hinged
plastic flagpole antenna.
But we're talking here about a minimum £15,000 investment a
for a 5-year contract with the absolute requirement of being
able to sell lots of airtime on a robust reliable signal.
So - if you can produce a 1kW transmitter that will perform to
Ofcom's satisfaction and an ATU that will handle that - you
have a customer sitting here waiting.
Ian Hickling
Partner
Office: 01635 578435 (7am-11pm UK time)
Carphone: 07530 980115 (only responds when driving)
6 Horn Street, Compton, NEWBURY, RG20 6QS
> Date: Tue, 15 Sep 2015 13:52:18 +0100
> From: office at fantasyradio.co.uk
> To: cma-l at mailman.commedia.org.uk
> Subject: [cma-l] AM community radio
>
> Afternoon all,
>
> For what it's worth, my own experience with AM is that
you can get some
> astonishing results! For several RSLs I have used a
wire antenna, (an
> inverted L) to great effect. The Earth mat consisting
of wire netting
> laid on the ground. Height is might as always, but even
with only 20
> metres, we were getting into Europe! I have reception
reports to prove
> it. I have also used a single 1 1/4" tube steel mast,
with a 'top hat'
> to increase top capacitance. I believe Radica used to
do AM antennae
> using a lamp post. (you can get a lamp post for about
£300) The
> standard RSL AM licence is for 1 watt. This gives a
similar coverage to
> FM at 25watts. Oh yes, and I designed and built my own
transmitters,
> using valves!
>
> Within the specified 5km radius for community radio, AM
will do the job
> nicely. (very important to get some good audio
processing though) Also,
> with fewer stations now on AM it could get better!
>
> Anybody want to know more? mail me at
phildawson at lemonmail.co.uk.
>
> Phil Dawson
> FANTASY RADIO97FM
> Devizes
> Wiltshire.
>
>
>
> On 15/09/2015 12:00,
cma-l-request at mailman.commedia.org.uk wrote:
> > Send cma-l mailing list submissions to
> > cma-l at mailman.commedia.org.uk
> >
> > To subscribe or unsubscribe via the World Wide
Web, visit
> >
http://mailman.commedia.org.uk/mailman/listinfo/cma-l
> > or, via email, send a message with subject or body
'help' to
> > cma-l-request at mailman.commedia.org.uk
> >
> > You can reach the person managing the list at
> > cma-l-owner at mailman.commedia.org.uk
> >
> > When replying, please edit your Subject line so it
is more specific
> > than "Re: Contents of cma-l digest..."
> >
> >
> > Today's Topics:
> >
> > 1. Re: AMCR - SDR (Associated Broadcast
Consultants)
> > 2. AMCR - SDR (Ian Hickling)
> > 3. Re: Confession (Two Lochs Radio)
> >
> >
> >
----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Tue, 15 Sep 2015 10:33:45 +0100
> > From: Associated Broadcast Consultants
<info at a-bc.co.uk>
> > To: The Community Media Association Discussion
List
> > <cma-l at mailman.commedia.org.uk>
> > Subject: Re: [cma-l] AMCR - SDR
> > Message-ID:
> >
<CAG9-nrYO5ZHtH6B54QmMBYS1VZqzLaSJD39dX4W_jqJ_g95C3A at mail.gmail.com>
> > Content-Type: text/plain; charset="utf-8"
> >
> > If anyone is interested I have Software Defined
Radio for sale on Ebay at
> > the moment. I've used the same type of unit to run
a DAB test multiplex.
> > I'm pretty sure I've recall that someone has
already written the code to
> > run it as a DRM transmitter.
> >
> >
http://www.ebay.co.uk/itm/HackRF-One-Software-Defined-Radio-NEW-Unopened-FREE-Postage-BARGAIN-/271983417851?hash=item3f537999fb
> >
> > I can't help feeling though that the SDR is the
"easy" part. The difficult
> > part is getting an efficient aerial system.
> >
> > 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
_______________________________________________
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
--
Local Reports at http://www.ravensound.pilgrimsound.co.uk
_______________________________________________
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/20150916/f5d33941/attachment.html>
More information about the cma-l
mailing list