Transmitter Section, Stage Analysis

TM 11-6625-667-45/NAVSHlPS 0969-249-8010/NAVAIR 16-30APM123-2/TO 33A1-3-367-22

The capacitor and resistors in the base circuit serve

effective result is an RF P2 pulse that has a mini-

the same purpose as described in (2) above for

mum amplitude 10 db below the PI1 and P3 pulses.

A16Q1.

With the ISLS switch at ON, the P2 pulse is

b. Transmitter Oscillator A16Q8. The trans-

directed to the main modulator driver and its RF

amplitude is approximately the same as the other

mitter oscillator (fig. 8-7) is crystal controlled,

pulses. The P2 pulse will appear at the trans-

and produces a 38.14815-mc, continuous wave (cw)

mitter output 2 microseconds after the P1 pulse.

signal. The collector tank circuit, consisting of

transformer A16Tl and capacitors A16C6 and

2-12 Transmitter Section, Stage Analysis

A16C7, is tuned by trimmer capacitor A16C6. The

RF output from A16T1 is coupled by capacitor

a. Modulator.

A16C8 to the control grid of first tripler amplifier

(1) General. The modulator (fig. 2-11) am-

A16V1.

plifies the P1 and P3 pulses and either amplifies

or attenuates the encoder P2 pulse. It then drives

c. First Tripler A16VI and Seccond Tripler

the transmitter RF output stage with these three

A16V2 The first and second triplers (fig. 8-7)

pulses. Main modulator A16Q1 and low P2 pulse

have their plate circuits tuned to three times their

modulutor A16Q2 perform these operations. En-

input frequency. The RF output of oscillator

coder pulses are applied to A16Q1 and A16Q2

A16Q3 is coupled to the control grid of A16V1.

when IS1S switch A16S7 is set to OFF, and

The plate tank circuit (T2, C12, and C13) is tuned

to 114.44445 mc (three times the input frequency).

A16Q1 is used only when this switch is set to ON.

The circuits of the two modulator stages are simi-

Trimmer capacitor A16C12 is used to tune the

lar except that A16Q2 has an output level control

tank circuit.. The RF output of A16T2 is coupled

(A16R6).

by capacitor A16C14 to the control grid of tripler

A16V2. Its plate tank circuit (T3, C17, and C18)

(2) Main modulator A16Q1. This stage am-

is tuned to 343.33335 me (three times the input

plifies the positive encoder P1 and P3 pulses. It

frequency) : trimmers A16C17 and A16C18 are

also amplifies the positive encoder P2 pulse when

used to tune the primary and secondary of trans-

sidelobe-suppression test is in progress (switch

former A16T3. The secondary of A16T3 couples

A15S7 is ON). The pulses that appears at the

the RF energy to the cathode of cavity tripler

base input are amplified and the resultant nega-

A16A1V1.

tive pulses are coupled to the transmitter output

stage (A16A1V1 ) cathode. Capacitor . A16C2 at the

d. Cavity Tripler A16A1V1. The cavity tripler

input neutralizes the storage-time delay to im-

(fig. 8-7) produces the pulsed RF interrogation

prove the risetime of the output pulse, Resistors

signal to be transmitted to the transponder set

A16R3 and A16R4 provide base bias. Resistor

under test. It is a tuned-cavity stage. with electron

A16R2 is a collector load, common to both

tube A16A1V1 housed in the cavity. The cathode

modulators.

of A16A1V1 iS biased with a positive voltage to

(3) Low P2 pulse modulator A16Q2. This

hold it at cutoff when pulses are not present. The

stage is used when the sidelobe-suppression test is

P1. P2, and P3 negative pulses from the modulator

not in progress (switch A15S7 is at OFF). It is

are applied to the cathode and each pulse causes

a pulse-level-control circuit t that reduces the am-

A16A1V1 to conduct for 0.8 microsecond. The

plitude of the encoder P2 pulse. Control A16R6 is

cavity is tuned to three times the RF input fre-

used to adjust the P2 pulse RF amplitude at the

quency from second tripler A16V2 to produce a

pulsed RF output of 1.030 mc. The frequency is

transmitter out put to at least 10) dbm below that

of the P1 and P3 pulses, The P2 pulses at the

tuned with the FREQ control on the cavity. A

power-level PWR control is also located on the

base input causes A16Q2 to conduct. This conduc-

cavity and is used to adjust the output power level

tion is controlled by control A16R6 in the collector

by changing the Q of the cavity. Power level is

lead which is in series with load resistor A16R2.

preadjusted between 15 and +4 dbm, depending

The pulse amplitude at the junction of these

on the equipment to be tested. Capacitor A16A1

resistors is determined by the setting of A16R6.

2-17