[Community Radio] Fwd: Transmitter siting and Directionality

[Bill Best]

-------- Original Message --------
Subject: Transmitter siting and Directionality
Date: Sat, 29 Jan 2005 13:10:04 -0000
From: Ian Hickling <transplanfm at hotmail.com>


We have been offered a suitable location for a studio but it is a mile 
or two to the south east of our ideal transmitter location which would 
be on the prow of the hill in Central Morley. Whilst we could get 
ourselves a microwave link it will be a while before we could justify 
and afford that.

>From my Ham Radio days I seem to remember aerials can be made directional  with careful design comparatively easily but the Ofcom guidance seems to assume an omnidirectional transmission in a five mile radius. Does anyone know if such an arrangement will be acceptable?

Rather than saying that aerials can be made directional, the reality is 
that aerials are vary rarely truly omni-directional- mainly because of 
the influence of the structure on which they are mounted.

We have considerable experience over the past 8 years of designing and 
building radio systems, including specialist coverage systems and the 
use of links.  Most full-time stations use directional coverage, and 
Ofcom will accept that a Community Radio station way require directional 
cover rather than simply trying to push its signal out in all directions.

In the Technical Requirements in Section 9a7 of the Application, you are 
invited to submit details of the antenna system you propose, and 
directional qualities are expressed in the Diagrams of Vertically and 
Horizontally Polarised signal component which are required to be submitted.

It is sensible to look for a well-elevated transmitter site for your 
project, as the likelihood of getting good coverage of your target 
audience with an aerial on top of your studio is pretty slight. You will 
therefore need a method of getting your output from the studio to the 
transmitter, and there are several options here.
You could rent a landline from BT or your local cable company and use an 
analogue or digital signal sending process; or use a radio link.

These are available in the 1,4 to 2,5 GHz bands at sensible prices, and 
the big advantage is that once installed you pay only an annual licence 
fee of under £200 rather than continuous line rental of about £6000 per 
annum.
The disadvantage is that links can occasionally fail - for any one of 
several reasons, and so a dialled IDSN line backup is conventionally 
installed for emergencies. The whole system comes out at around £9000 
but prices are falling regularly for this type of equipment.

We would be pleased to receive enquiries of this nature and about any 
requirements you may have for transmission and studio equipment for 
Community Radio projects.

Ian Hickling
Transmission Director
transplan UK

ian at transplan.uk.com<mailto:ian at transplan.uk.com>