500 WATT RADIOBEACON TRANSMITTER
ND2000A-02X-xx0
Page
3-2
15 January 2005
3.3.4
ELECTRICAL POWER CABLING:
The ac power cable must be provided by the user. A
dc power cable, (if applicable) must also be provided
for the user. The ac power cable enters the cabinet
through a cable entry hole in its lower, rear, right-
hand side and terminates at terminal board TB1. If
applicable, the dc power cable enters the cabinet
through a cable entry hole in its lower, rear, left-
hand side and terminates at terminal board TB2 (see
figure MD-38).
3.3.5
RF FEED CABLE:
The RF feed cable
must be a 50 ohm coaxial cable that is terminated by a
type
N
coaxial connector. The RF output connector of
the transmitter is located on the outer, top section of
the transmitter cabinet.
3.3.6
CONTROL/MONITOR
CABLING:
The control/monitoring cable enters the cabinet
through a cable entry hole on the top of the transmitter
cabinet (left or right side), are passed through a ferrite
toroid and terminate on terminal boards TB3 and
TB4. The ferrite toroids are available at either end of
the interface panel assembly (see figure MD-29) and
provide protection for the transmitter from lightning
induced voltage transients. Terminal boards TB3/TB4
are accessible from the rear of the transmitter cabinet.
Refer to figure MD-38 for information to assist in
determining cable length.
3.3.7
VENTILATION:
The interior of the
transmitter enclosure must contain a ventilation
system that will ensure the inside temperature does
not 55
°
C.
3.3.8
HEATING:
The interior of the transmitter
enclosure must contain a heating system that will
ensure the inside temperature does not go below -
10
°
C.
3.3.9
WORK AREA:
It is recommended that a
suitable work area be provided adjacent to the
transmitter to permit bench inspection/repair of
removable assemblies.
EXTERNAL INPUT/OUTPUT CIRCUIT
REQUIREMENTS
(see figure 3-2)
:
3.4
The external input (audio and control) and
output (status and alarm monitoring) circuits must
comply with the following:
3.4.1
EXTERNAL AUDIO SOURCE:
An
external audio source must be provided. The
impedance of the audio source must be a balanced
600 ohms. The audio signal applied to the transmitter
must be between -20 dBm and +20 dBm. The user
determined limits are between 0 to 95 % modulation.
3.4.2
REMOTE CONTROL CIRCUITS:
The
transmitter's on/off status and its RF output level can
be controlled remotely. There is also provision to
remotely switch from main to standby, as a test
function, to verify the standby transmitter is
serviceable and to activate the standby '1' and standby
'2' code variations. When these remote controls are
used, the following must be observed:
3.4.2.1 Standby '1' and Standby '2' Controls:
The stby 1 and stby 2 (side
A
and side
B
) switching
circuits should be the equivalent of normally open,
single pole, single throw switches. When in the
closed position, each switch should apply a ground to
the appropriate terminal of barrier strip TB3 (see
figure 3-2).
3.4.2.2
Battery Reset Control:
When required,
the battery reset switch should be a normally open,
single pole, single throw, spring-loaded switch. When
held in its closed position, it shall apply a ground to
TB3-17.
3.4.2.3
Power Trim 'A' and 'B' Controls:
The
A
and
B
power trim control inputs are intended to be
provided by a remote maintenance monitoring
(RMM) system. It shall p15 volts DC to
TB4-10 for side
A
and to TB4-11 for side
B
when the
intended carrier level is desired. If an RMM system is
not used, connect TB4-10 and TB4-11 to +15 volts
DC.
3.4.2.4 Remote
Off
Control:
The rmt off control
switching circuit should be the equivalent of a
normally open, single pole, single throw switch.
When set to its closed position (tx off), it shall apply a
ground to TB3-19.
3.4.2.5
A/B Main Select Control:
The A/B main
select switching circuit should be the equivalent of a
normally open, single pole, single throw switch.
When set to its closed position, it shall apply a ground
to TB3-18.
