Section III. DETAILED FUNCTIONAL DESCRIPTION NDB TRANSMITTER

TM 11-5825-271-34

mental changes The increase/decrease switch S4 is

impedance to the ATU. The loading coils tune the

connected to the servo probe A2 and permits manual

reactive component of the antenna impedance for the

slewing of the tuning drive. When switch S4 is operated,

frequency in use, while the servo probe A2 and tuning

the automatic tuning function is bypassed.

motor provide the automatic fine tuning. The rf output

e. The matching transformer matches the antenna

from the loading coils is applied to the antenna.

Section III. DETAILED FUNCTIONAL DESCRIPTION

NDB TRANSMITTER

output and nominal ac line voltage.

2-13. Transformer Chassis Assembly (fig. FO-3)

b. 24V Regulator. The unregulated +50V from

a. All external connections to the NDB transmitter,

current shunt R12/R13/R25 is applied, through fuses F2

except the rf output, are made through TB1 and TB2.

and F3, to two series regulators comprising Q3, Q4, Q5

The power supply AlA1 Is connected to XA1, and TB3

and associated components.

Zener diode CR8

provides connections to the wiring harness within the

establishes a 24.7V reference at the collector of Q3. The

NDB transmitter.

resulting +24V at the emitter of Q4 is applied directly to

b. Choke L1 provides smoothing of the unregulated

power light DS1 and to P1-21 as the transmitter dc

50 Vdc supply from the power supply A1A1 through XA1,

supply. Zener diode CR9 is normally reverse-biased and

pins 23 and 14. Transformer T1 can be wired for 115

serves as a safety device to prevent the emitter voltage

Vac or 220 Vac primary power and supplies the following

of Q4 from rising above + 28V in the event Q3 or CR8

voltages to XA1:

become open circuits. Series regulator Q5 provides a

(1) 20 Vac between XAl-1 and XA1-2

regulated dc voltage slightly less than + 24V This 24V

(2) 108-120 Vac between XA1-16 and XA1-13.

output is used as the ATU supply and for remote status

c. Secondary taps 7, 8, and 9 and 11, 12, and 13 of

dc monitoring. Fuses F2 and F3 provide protection for

T1 are selected according to the nominal ac input line

the regulated 24V outputs.

voltage as follows

c. Battery Charger.

The input to the battery

Nominal Line Voltage T1 Taps

charger circuit is the unregulated dc output from full-

107 Vac (214 Vac)

7 and 13

wave rectifier CR1/CR2, applied through the transient

118 Vac (236 Vac)

8 and 12

suppressor network R5/RV1. The voltage at the base of

131 Vac (262 Vac)

9 and 11

Q2 is set by R7, Q1 and CR3. The current through Q2 is

restricted by the voltage drop across R11. When the

2-14. Power Supply A1A1 (fig. FO-4)

voltage drop across R11 exceeds 0.7V, diodes CR4 and

a. Power On/Off. The 115 or 230 volt ac input is

CR5 are forward biased and, form a current bypass for

applied to transformer T1 on the transformer chassis

the Q2 base supply. Initially, with the POWER ON/OFF

assembly (fig. FO-3) through the POWER ON/OFF

switch S1 closed, he charge is at a constant current. As

switch S1 and POWER fuse F1. The output from the

the battery voltage rises, the charging current decreases,

center-tapped secondary winding of T1 is applied to full-

tapering off to zero when the battery becomes fully

wave rectifier CR1/CR2 The voltage across TP1 and

charged.

TP2 is 114 Vac nominal, and the voltage from TP1 or

d. Battery Switch. The battery switch consists of

TP2 to ground is approximately 57 Vac. The dc from the

Q6, Q7, and Q8 and associated components. Under

cathodes of CR1/CR2 is smoothed by L1 on the

normal conditions (ac present), the battery switch

transformer chassis (fig. FO-3), and then routed through

isolates the battery's positive terminal at P1-4 from the

the current shunt (R12/R13/R25) to P1-11 The

unregulated dc input at P1-23. The ac supply P1-13 is

unregulated dc, approximately +50 vdc, from the current

rectified by CR7/C1 and applied to the base of Q6

shunt is also fed to the 24V regulator The outputs at P1-

through voltage divider network R21/R22. This causes

6 and P1-7 are used for metering and indicate the

Q6 to conduct, and Q7/Q8 to cut off. In the event of ac

current load on the power supply The unregulated +50

failure, Q6 switches off because ac voltage at P1-13 is

Vdc at P1-11 is applied to the pa module Al A4; this

no longer present, and Q8 is turned on by the battery

voltage varies with ac line variations and output power

voltage through R23. As a result, Q7 conducts and con-

setting, but should be approximately +50V at full power

2-5