4011 FILTER/DIPLEXER

TM 11-5820-918-13

4-45. The AC line input from the rear panel is RF filtered by FL1 and presented to

the primary of transformer T1 via an input voltage selector switch (SW1). The selec-

tor switch is factory wired to the 115/230-volt terminals of T1. Some variations of

input voltages can be accommodated by changing transformer connection points as

indicated by the values shown at the taps of transformer T1 primary. Also connected

to the primary side of T1 are the AC-to-AC converters. These units are separately

filtered and convert 107 VAC at 47-440 Hz to 115 VAC at 60 Hz. They provide constant

cooling fan speed regardless of the input line frequency. The secondary winding

of T1 supplies voltage to five full wave bridge rectifiers (CRl-CR5). These rectifiers

supply 35 volts to the five voltage regulators (A1-A5). Each regulator is factory set

to supply 27.2 .2 VDC to the 100-watt amplifier assembly (2A1). Regulators A1-

A4 supply power to the four 30-watt amplifier circuits, and A5 supplies power to the

driver circuit. A single 5-volt regulator (U4) supplies power to the front panel power-

on lamp. Each 27 VDC regulator is connected to a thermostat on the 100-watt amplifier

assembly. If the temperature on the amplifier assembly exceeds safe operating limits

(215F) , the thermostat contact opens. With the thermostat contacts open, regulators

A1-A5 are disabled.

NOTE

The 100-watt amplifier assemblies (5018- 1001) (S/N 400100 and before)

do not have the thermal protection and must be modified when used

in 5018 amplifier units with S/N 400101 and above. Connector 2AlJ4,

pin F must be connected to chassis ground. If this pin is not grounded,

the 27 VDC regulators will be disabled due to the thermal shut-off feature.

4-46.

4011 FILTER/DIPLEXER - UNIT 3

4-47. The filter/diplexer (figure FO-2) consists of five main assemblies: filter set

(3A1A1); filter decode (3A2A2); power detector (3A1A3); diplexer (3A1A2); and power

Supply (3A2A1). The power detector is a 30-dB, high frequency, directional coupler/

detector which provides output voltages related to the forward and reflected powers.

These voltages are used to drive the 1024 front panel RF power meter. Included in

the 4011 are two relays which together allow diplexed or non-diplexed (direct) opera-

tion (figure FO-2).

4-48. FILTER SET (figure FO-25) (S/N 400101 and on). The filter set consists of

eight sequentially enabled, half-octave, low-pass filters which are used to attenuate

harmonics generated by the 5018 power amplifier. The filters are located on two cir-

cuit cards (3A1A1A1 and 3A1A1A2) within the filter set. The filters are designated

LPF1-LPF7 and LPF9; LPF8 is a switchable bypass circuit that feeds the RF signal

directly to LPF9. Filters LPF1-4 are located on the A2 assembly and LPF5 thru LPF9

are on the A1 assembly. The RF signal enters at J1 and is connected to E10 and E12

on the A1 and A2 assemblies respectively. If the signal is between 2.0- 2.8 MHz, LPF1

is enabled. This is accomplished by enabling the input (CR10) and output (CR12)

diode gates with forward biasing. This 5-volt bias is provided at E1 by the filter

decode assembly. The remaining seven pairs of diode gates are reverse-biased by

a -250-volt potential also provided by the filter decode. As the RF sweep signal passes

2.8 MHz, CR10 and CR12 in LPF1 are reverse-biased by -250 volts, thereby removing

LPF1 from the RF circuit. Due to the permanent bias of -240 volts at E9, CR11 is

now forward-biased, shunting to ground any RF that leaks through CR10. As the

RF signal sweeps up to 30 MHz, LPF2 thru LPF8 are sequentially enabled in a similar

manner. The tabulation below indicates the frequency range during which each circuit

is enabled.

4-15