Functional Block Diagram Description of Receiver, Radio R-1467/GK-144 70 MHz IF Amplifier Circuits

TM 11-5820-695-35

signal from bandpass filter 2FL21 is applied to one input

2-22.

Functional Block Diagram Description of

of crystal mixer 2A8Z1 and the 220 MHz signal from

Receiver, Radio R-1467/GK-144 70 MHz IF

2A13 is applied to the input of 220 MHz bandpass filter

Amplifier Circuits (fig. 5-19)

2A8FL1. The output of 2A8FL1 is applied to the other

input of crystal mixer 2A8Z1. The two signals are mixed

70 MHz Bandpass Filter 2A6. The 70

producing the 4.33 to 5.07 GHz signal which is 170 MHz

MHz bandpass filter 2A6 is a five pole gauss filter ,which

away from the 4.4 to 5.0 GHz rf input frequency. The

in a bandpass has a center frequency of 70 MHz and a

4.33 to 5.07 GHz output is applied through coaxial

5.0 MHz bandwidth. The insertion loss at 70 MHz ( 0.5

circulator 2A8HY1 to local oscillator bandpass filter

kHz) is 2.0 db maximum. The 70 MHz signal from

2FL6 where the correct frequency (f below) is selected.

amplifier-mixer 2A7 is passed through 2A6 to 70 MHz if

Coaxial circulator 2A8HYI has a passband of 4.33 to

amplifier 2A5.

5.07 GHz and provides isolation between crystal mixer

2A8Z1 and local oscillator bandpass filter 2FL6. The

70 MHz IF Amplifier 2A5. 70 MHz if

crystal current outputs of crystal mixer 2A8Z1 are

amplifier 2A5 is comprised of amplifiers, agc, metering,

applied to the meter selector switch through crystal

and if monitor circuits.

current metering circuit to the FREQ MIXER CURRENT

1 and FREQ MIXER CURRENT 2 positions of meter

(1) The 70 MHz amplifier circuits amplifies

selector switch mounted on meter panel assembly

the low level 70 MHz if input signal for application to

2A15A2 and variable resistors 2A15A2R3 and

demodulator 2A4. The IF GAIN control, at the input to

2A16A2R4.

Variable resistors 2A15A2R3 and

amplifier stage Q1, is used to set the 70 MHz if gain.

2A16A2R4, mounted on the rear of meter panel

The 70 MHz if signal is amplified by cascaded amplifier

assembly 2A15A2, are used to calibrate the FREQ

stages Q1 through Q5 and attenuated by diode

MIXER CURRENT 1 and the FREQ MIXER CURRENT

attenuator circuits CR1 through CR4. The amplified 70

2 meter indications.

MHz if signal from amplifier stage Q5 is then fed to

buffer amplifier Q6. The overall gain of cascaded

Local Oscillator Bandpass Filter 2FL6.

amplifier stages Q1 through Q5 and diode attenuator

Local oscillator bandpass filter 2FL6 is a four-pole (four-

circuits CR1 through CR4 is controlled by the agc circuit.

cavity) rf bandpass filter which passes only the desired

Buffer amplifier Q6 provides an impedance match

translated frequency from receiver frequency mixer

between amplifier stage Q5 and output amplifier Q7.

stage 2A8. Each of the four tuning cavities is ganged to

Output amplifier Q7 provides a linear power output level

a single frequency adjust control dial with direct readout

of the 70 MHz if signal which is sent to the age circuit

of the incoming rf frequency (frequency to which the

and to demodulator 2A4.

receiver is set). However, the actual bandpass of 2FL6

is separated by 70 MHz from the incoming rf

(2) The agc circuit controls the overall gain of

frequency.

amplifier stages Q1 through Q5, and maintains each if

amplifier output at the same if level ratio as at the if

(1) For example, if the dial on 2FL6 is set to

amplifier input. The agc circuit consists of peak detector

4500 MHz, 2FL6 is tuned to the difference frequency

CR5, CR6, AGC SEL switch S1, dc amplifier Q8, Q9,

component (4430 MHz) which is 70 MHz below the

and emitter follower Q10. TAGC SEL switch S1 is used

incoming rf frequency (4500 MHz - 70 MHz = 4430

to select the age mode and connects the proper inputs

MHz). The 4480 MHz signal is passed by 2FL6 to

to the agc circuit. When AGC SEL switch S1 is in the

amplifier-mixer 2A7 (para 2-20d).

TEST position, the age circuit is disabled and maximum

if gain is obtained. In the DIV OFF position, the dc

(2) If the dial on 2FL6 is set to 4800 MHz,

output of the peak detector CR5 and CR6 is applied to

2FL6 is tuned to the sum frequency component (4870

meter circuit R32 and R37 and to dc amplifier Q8 and

MHz) which is 70 MHz above the incoming rf frequency

Q9. The DIV ON position is not used because the R-

(4870 MHz - 4800 MHz = 70 MHz). The 4870 MHz

1467/GRG 144 is a single channel receiver.

signal is passed by 2FL6 to amplifier-mixer 2A7 (para 2-

amplifier Q8 and Q9 amplifies the dc voltage at its input

20d).

to control the level of the dc gain voltage applied to

diode attenuator circuits CR1 through CR4. The output

of the dc amplifier is applied to emitter follower Q10

through AGC GAIN potentiometer which sets the dc gain

of the age circuit.

2-49