MAIN/STANDBY 125 WATT RADIOBEACON WITH NDDS/T
(INSTALLED
IN NARB07 CABINET)
IS02001 (Page 1)
29 January 2002
INTRODUCTION
1.
When two ND500II 125 watt radiobeacon
transmitters and an NDDS/T Dual Direct Digital
Synthesizer (DDS) are installed in an NARB07
cabinet, some mechanical information in the
transmitter's instruction manual must be changed and
the cabinet's electrical information is required. This
document identifies the mechanical differences. It
also provides an electrical parts list and point-to-point
wiring information for the cabinet. It is recommended
that, where replacement pages are not provided,
affected areas of the transmitter instruction manual be
highlighted using a suitable marker, or changed using
pen and ink, to ensure users of the manual are aware
of the differences.
MECHANICAL DIFFERENCES
2.
The drawer slide depicted in figure MD-17
of the transmitter instruction manual has been
replaced with a different type of slide. It is not
possible to swivel the transmitter when using this
slide. All references to rotating the transmitter when
it is extended on its drawer slide must be ignored. If it
is not possible to access a specific area of a transmitter
when it is extended on its drawer slide, the transmitter
must be lifted off its slides and placed on a work
surface.
CABINET DESCRIPTION
(see figure 1):
3.
The cabinet is 30 inches high, 21 inches
wide and 24.5 inches deep. It houses two ND500II
radiobeacon transmitters and an NDDS/T. The upper
transmitter is designated as the
A
transmitter, while
the lower transmitter is designated as the
B
transmitter. The cabinet also contains a type N RF
coaxial connector (J1), which is the RF output
connection point for the RF feed cable; two AC power
duplex receptacles; a two-pole, double-throw switch
(S1) that selects which transmitter will be the
main
transmitter; three barrier strips (TB1, TB2 and TB3),
which are used as the external wiring interface; and
the interconnecting wiring. Refer to figure 3 for an
electrical schematic of the cabinet.
THEORY OF OPERATION
4.
The theory of operation presented in the
ND500II instruction manual describes the operation
of both transmitters. The following provides a brief
description for when they are connected in a
main/standby dual installation. See figure 3 of this
information sheet for system interconnection.
NOTE
The upper transmitter (ND500II-113-x20) is identified
as the A transmitter and the lower transmitter
(ND500II-013-x20) is the B
transmitter. The A
transmitter's harmonic filter contains a relay that
routes the RF output of the active transmitter to the
antenna system.
4.1
MAIN TX OPERATION:
When the
main
transmitter, as selected by the (S1)
SELECT MAIN
TX
switch, is turned on and producing a satisfactory
RF output; the following will occur:
(a) The source voltage for the NDDS/T's
24VDC
inputs will be provided by the selected
main
transmitter. The NDDS/T will provide a RF
signal at the transmitter's operating frequency to
J3 (Ext RF Drive) of the selected main
transmitter.
(b) 15VDC, from TB2-1 of the
main
transmitter,
will be applied to TB1-6 of the
standby
transmitter as its
standby off
control signal.
(c) If
the
A
transmitter is the
main
transmitter, the
main/standby relay in its harmonic filter will be
energized. If the
B
transmitter is the
main
transmitter, the main/standby relay in the
A
transmitter's harmonic filter will be de-
energized. The selected
main
transmitter's RF
output will be routed to the cabinet's
RF OUT
coaxial connector (J1).
(d) The source for the antenna tuning unit controls,
at TB3-6 thru TB3-10 (
ATU CONT
) of the
cabinet's customer interface assembly, will be
the selected
main
transmitter.
(e) The selected main transmitter will be providing
the 'audio out' (RMT AUD) sample.
