FM Transmission Systems

Coverage

There are several factors influencing the coverage area:

· Location of the transmitter in relation to the desired coverage area

· Type and ‘pattern’ of the transmitting aerial

· Height of the transmitting aerial

· Power of the transmitter (and this is regulated in most countries)

· Terrain (how hilly is the area to be covered)

Transmitters

Transmitters are available with powers of a few Watts to several thousand Watts. A 50W transmitter may cover a small village or town
(if the aerial is high enough), whereas to cover a large city may require 5kW.

When selecting a transmitter the following parameters should be considered:

· Efficiency (there is no point paying for power which does not go into the aerial)

· Robustness (a modular design makes sense – a single failure will not render the whole unit inoperative)

· Remote control and diagnostics (often transmitters are sited in remote locations, difficult to get to)

What else is required?

In addition to the transmitter itself, several other components are required. An FM Processor is used to make your station sound ‘louder’ than its competitors, RDS allows data to be transmitted and displayed on suitably equipped receivers, a cavity filter reduces spurious emissions (and may be a regulatory requirement). Aerials need to be chosen carefully to ensure optimum coverage, connected with suitable ‘feeder’ cable to avoid losses.

More sophisticated systems will have back up transmitters with varying levels of change-over system. Dummy loads allow the transmitter to be tested independently of the aerial and feeder cable.

In situations where the transmitter is not located at the studio site, a Studio to Transmitter Link (STL) is required to get the signal from the studio to the transmitter.

Clyde Broadcast offers a selection of transmitter packages using carefully selected components from leading suppliers.

Coverage prediction plots

Coverage prediction plots are highly recommended. Based on the planned location and height of antenna, a coverage plot will let you know how far your signal will travel, taking into account local terrain. If this can be married to a population map, you can get a very good idea of the number of people who will be able to hear your station.

How can clyde help?

We can assist with the design, supply and installation of the transmission equipment, as well as providing training on its operation and maintenance.

We can also provide coverage predictions, and can offer advice with standby transmitter arrangements, STL, power conditioning and remote support options.