Eddystone S79005 Installation And Operation Manual - page 5
Print Date 08/04/14 Page 5 of 34 S79005-00MA-05
SECTION ONE : INTRODUCTION
! CAUTION !
This Transmitter operates at
high RF power levels, internal supply energy levels and mains
supply current levels. It also incorporates devices containing toxic BeO. Installation, operation and
maintenance of this unit must therefore, only be carried out by suitably qualified personnel, familiar
with and fully utilising the safety procedures such equipment demands.
NO attempt at installation should be made without full reference to and compliance with SECTION
TWO : INSTALLATION.
NO attempt at internal maintenance should be made without full reference to and compliance with the
appropriate sections (apart from fuse changing which is detailed in INSTALLATION).
1.1 : GENERAL DESCRIPTION
The S79005 Low Power FM Transmitter provides output power of up to and including 500W (used
singly) or 1kW (using combined pairs) in the standard Band ll frequency range of 87.5-108MHz. It is
normally supplied with either one or two Exciters, capable of generating a standard mono or stereo FM
signal from a variety of analogue or digital audio or data sources (including left/right audio, MPX, RDS,
SCA, DARC etc.). It is important to note that the Exciter(s) supplied will depend on the user’s actual
requirements in this regard which, therefore, must be clearly specified at time of ordering.
The Transmitter is totally self-contained (including forced air-cooling) and can be mounted as a
complete unit (less Exciters) within a standard 19 inch rack with at least 600mm depth and 7U height.
All that is required is a connection to a mains supply, to an antenna and to the Exciter/Drive(s). When
used in pairs, to generate up to 500W, an additional two-way splitter, combiner and approximately
250W balance load is also required. In this situation, additional manual ‘patching’ or manual/automatic
switching can be provided, as an option, to direct all of one Transmitter’s power to the antenna.
The key feature of The S7900 series is its ability to remain ‘on-air’. The use of multiple Amplifier and
(apart from the S79005-01 and -03) Power Supplies Modules and dual power supply and control
circuitry means that if failures do occur, it normally only results in a reduction of output power.
Furthermore, the lightweight, hot-pluggable Amplifier and Power Supply Modules can be easily
replaced, in seconds, without having to go ‘off-air’ (again, apart from the Power Supply on the S79005-
01 and -03). Provision for dual Exciter/Drive automatic changeover and for connection to a second
active/passive reserve S76XX or S79XX (i.e. 500W to 10kW) Transmitter is also made, further
enhancing the ability to remain ‘on-air’.
Each Transmitter consists of a number of modules described as follows (1.1.1 – 5 inc.). Front and rear
views, block and circuit diagrams, showing these modules are bound at the rear of this manual
(S79005-00GA, S79005-00BK and S79005-00CT).
Workshop editions of this manual contain extra information, also bound at the rear, which gives
detailed test procedures, circuit diagrams, assembly diagrams, layouts and parts lists.
1.1.1 : E2021 300W Amplifier Module
Two of these are provided, each with their own independent control and monitoring circuitry. This
circuitry includes reverse power, supply current and temperature monitoring to shut down and protect
individual modules. Failure of a single Amplifier Module gives an approximately 6dB reduction in
power, with the Transmitter still operating.
Each Amplifier Module can be removed or replaced whilst the Transmitter is operating (‘hot-
pluggable’). This feature means that if failures do occur, modules can be replaced within seconds,
without having to go ‘off-air’. Red/green fault displays on the front of each module help indicate the
faulty module to be replaced, this normally restoring the Transmitter’s full output without any further
immediate technical investigation being required. The relatively low weight and small size of each
module assist their actual transport to site.