SRK FMA300 User Manual
(ACN 089 050 564 ABN 44 089 050 564)
8 Victoria Grove
Hawthorn East
VIC 3123
Australia
FMA 300 Manual
Safety notice
1 General description
2 Unpacking
3 Installation
4 Operation
4.1 Front view
4.2 Rear view
4.3 Switching on and off
4.4 Setting output power
4.5 Setting channel frequency
4.6 Setting audio gain
4.7 Selecting pre-emphasis and input impedance
4.8 Enabling/disabling stereo
4.9 SCA option
4.10 Protection
4.11 Remote operation
4.12 Audio limiter
4.13 Amplifier metering
5 Maintenance
5.1 Recommended maintenance schedule
6 Circuit description
6.1 Equipment overview
6.2 Amplifier
6.3 Control Board
Drawings
FMA300 Manual
2003 SRK Electronics Pty Ltd
FMA 300 Manual
Safety note
This equipment uses high voltages internally. Any servicing should be performed by
competent individuals.
Prolonged exposure to high level RF radiation has been shown to pose a health risk.
Whilst the equipment is intrinsically safe, its use in conjunction with an antenna
system may generate large RF fields. Appropriate precautions should be taken by
individuals that habitually work close to the transmitting antenna.
The RF power devices of this equipment employ Beryllium Oxide. This substance is
extremely toxic if pulverised. On no account should any RF power devices be
smashed. Please refer to attached Material Safety Data Sheet for further information.
WARNING
THIS EQUIPMENT IS SUPPLIED WITH A MAINS LEAD INCORPORATING
AN EARTH WIRE. IT IS IMPERATIVE THAT THIS EQUIPMENT IS
CONNECTED TO A MAINS OUTLET THAT HAS AN EARTH. IN
COUNTRIES WHERE EARTHED OUTLETS ARE NOT MANDATORY, IT IS
THE CUSTOMER’S RESPONSIBILITY TO ENSURE THAT THIS
EQUIPMENT IS APPROPRIATELY EARTHED.
2003 SRK Electronics Pty Ltd
FMA 300 Manual
1 GENERAL DESCRIPTION
The FMA300 is a high quality 300W amplifier intended for audio broadcast service in the FM
band.
Its features include:
• Frequency agile.
• Extensive self test and auto diagnostics.
• Rugged design.
• Conservatively rated.
Applications include low power broadcast, narrowcast, community broadcast, rebroadcast for
tunnels, student radio stations and as a driver for high power transmitters.
The FMA300 is designed and built in Australia.
2003 SRK Electronics Pty Ltd
FMA 300 Manual
2 UNPACKING
This section details the way in which the FMA300 should be unpacked upon receipt by the
customer.
Upon receipt the amplifier should be visually inspected to ensure that no damage has
occurred in transit.
Along with the amplifier, the following items should also be present:
• This manual
• Mains lead
The customer should ensure that all items are present and then store them in a safe place.
2003 SRK Electronics Pty Ltd
FMA 300 Manual
3 INSTALLATION
3.1 General
This section describes the installation and infrastructure requirements for the FMA300.
Departure from the instructions contained herein may void any warranty provided by SRK.
3.2 Environmental
The transmitter is intended for indoor use. The transmitter should be protected from rainfall
and direct sunlight, extremes of temperature and humidity and from conditions of high dust
levels. Ambient temperature should be in the range +10°C and +30°C. The transmitter shall
not be operated at altitudes in excess of 3500m above sea level. The transmitter must be
installed on a flat, stable surface. The transmitter must be installed in the upright position.
The transmitter must be installed in a location free from vermin and the ingress of other
animals. The transmitter shall not be installed in locations prone to flooding. All ventilation
orifices must be clear to allow adequate air flow.
3.3 Electrical supply
The electrical supply to the transmitter must be of the voltage, form and frequency described
in the specifications. All electrical wiring must be carried out in accordance with local laws,
standards and regulations. If power supply voltages regularly fall outside specifications then
a voltage regulator must be installed between the supply inlet and the transmitter.
3.4 Earthing
Adequate earthing of the transmitter is vital to ensure long term reliability and user safety.
The electrical supply must be earthed, via the earthing pin of the IEC connector. In countries
where power outlet earthing is merely optional, an earthed outlet must be used. See safety
notice at the front of this manual. A separate, independent, earth is required for the
transmitter/antenna system and must be connected to the earthing point indicated on the rear
of the transmitter. The cable used to connect the earth should be as thick as possible, with 8
AWG being the smallest size acceptable. Where possible, broad earthing band should be
used.
In addition to the earth connection to the transmitter, the outer conductor of the coax feed to
the antenna should be connected to the earth, as indicated below.
The earth itself must be of high quality buried copper, at least 1.5m deep and preferably in
ground that is habitually humid (eg, the base of a gutter down pipe).
2003 SRK Electronics Pty Ltd
FMA 300 Manual
3.5 Antenna
The antenna load connected to the transmitter must be tuned to minimise reflections. Whilst
the transmitter is designed to withstand high levels of reflection for short periods, continually
high levels of reflected power will degrade the long term reliability of the transmitter.
Operating SWR should be kept to below 1.9:1.
2003 SRK Electronics Pty Ltd
FMA 300 Manual
4 OPERATION
4.1 Front View
Please refer to figure 4.1. The numbers of the following paragraphs refer to the controls
shown in figure 4.1.
1 Auxiliary power indicators
These three LEDs indicate that the +5V,+15V and –15V auxiliary supplies generated within
the amplifier are present.
2 Amplifier meter
Displays various internal parameters of the amplifier, as determined by the meter parameter
panel (5).
3 Alarm indicators
When lit, these indicators show that an alarm or failure condition exists. The cause of any
alarm should be investigated.
4 Air inlets
These inlets allow air to enter the amplifier for cooling and must not be obstructed..
5 Meter parameter panel
This indicates which parameter is currently being displayed on the meter.
6 Meter parameter button
Pressing this button causes the meter to display the next parameter, shown on the meter
parameter panel.
4.2 Rear View.
Please refer to figure 4.2. The numbers of the following paragraphs refer to the controls
shown in figure 4.2
7 RF out
This is the RF output connector and mates with a male N type.
8 Amplifier forced air exhaust
This is the exit port for the forced air cooling. Do not obstruct.
2003 SRK Electronics Pty Ltd
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