500 WATT RADIOBEACON TRANSMITTER
ND2000A-02x-xx0
Page 2-18
15 January 2005
2.10.1.1 Low Battery Voltage Monitor:
When
operating from an external dc power source (battery),
the AC sense inputs on P1-7 and P1-5 are removed.
Transistors A1Q1/A1Q2 are turned on and relays
K2/K3 energized. If the battery voltage discharges
below the desired
Low Battery Threshold
(nominally
-42 V dc), transistors A1Q1/Q2 shall turn off. Relays
K2/K3 shall de-energize and the transmitter will shut
down. Potentiometers A1R7/R8 set the bias level on
the bases of transistors A1Q1/Q2 and therefore
establish the desired
Low Battery Threshold
(adjusted
at the factory when -42 volts DC is present on the
anodes of zener diodes A1CR3/ A1CR4).
2.10.1.1.1
Recharging of the dc power source
(battery) will not result in the transmitter
automatically turning on.
2.10.1.1.2
BATTERY RESET
switch S1 must be
momentarily closed (ground) for a nominal three to
five seconds. When
BATTERY RESET
switch S1 is
momentarily closed, relay K1 will momentarily
energize and the associated modulator's storage
capacitors will begin to charge through limiting
resistors R2/R3 towards the battery voltage. The B-
Vdc (
B
) and B- Vdc (
A
) output on connectors J1-
12/J1-10 are inhibited by the contacts of relay K1.
When the B- Vdc levels on connectors P1-8/P1-4
reach the desired level (greater than -42 V dc),
transistors A1Q1/A1Q2 will be forward biased
(turned on). Relays K2/K3 will energize and the
transmitter will resume normal operation on the
selected main-side (A or B, dependent on the position
of the
SELECT MAIN TX
switch) using the dc power
source as the transmitter's B- supply.
