DRAKE SPR-4 Dokumentacja Pobierz pdf (Strona 32)

6.4.4 CIRCUIT DESCRIPTION

The transceive switch on the T-4/T-4B/T-4X/T-4XB Transmitter

controls

the TA-4 by applying a negative or positive D.C. potential to the injec-

tion

cable

When the transceive switch on the transmitter is in SPOT

position, no D.C . potential is applied to the injection

cable

and the

injection

cable

is not utilized . In SEPARATE position, the injection line

is connected to the mute

jack

through a 68 K resistor. The mute

jack

the SPR-4 becomes positive under

open

circuit (receiver

muted)

condition

which supplies base current through R6,

CR2

and CR3 to

and turns it

on.Whenever, Q2 is on, Ql, Q3 and Q4 are also conducting. The

col-

lector current in Q4 drops the gate voltage on the SPR-4 premixer transis-

tor Q5 and cuts it off which éliminates the possibility of the SPR-4 in-

jection frequency from getting into the transmitter and causing a spurious

signal.

In RCVR position, the cathode of the premixer tube, V8, in the

T-4/T-4B/

T-4X/T-4XB Transmitter

connected directly to the injection line which

makes it positive, but not enough to cause CR2 to conduct preventing Q4

from disabling the SPR-4 premixer.

T-6 in the SPR-4, drives

Q5, an

emitter

follower, through

and R-12 in

the TA-4.

The output of Q5 drives the injection

jack

through C7 which

allows the T-4XB to transceive on the SPR-4

dial

frequency.

In XMTR position, the injection line is made negative which turns on Q1,

Q3 and Q4.

Collector

current in Q4 drops the gate voltage on the SPR-4

premixer transistor Q5 and cuts it off.The injection frequency signal

from the transmitter drives the

center

tap on the link of T6 through Q1

which is used as a switching diode.

in the TA-4 ,is an audio transformer which matches the SPR-4 audio

out-

put impedance to the anti-vox circuit in the transmitter.

6.4.5 SERVICE DATA

A voltage

chart,

schematic,

and circuit board layout, Figure 18

are

provided for servicing the TA-4.

6.4.6 ALIGNMENT

The carrier oscillator in the T-4XB must be adjusted

SO that the SPR-4

and the T-4XB

will

transceive.

Both SPR-4 carrier oscillators must be

frequency .

The SPR-4 oscillators are set at the factory and should

not require

any adjustment

If the SPR-4 alignment is under suspicion,

perform the

kHz IF and 5645 kHz IF alignment described in 5.3.l

and 5.3.2.

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