Function al Block Diagram Description of Receiver, Radio R-1467/GRC-144 RF Input and Mixer Circuits

TM 11-5820-695-35

diode assembly above a predetermined temperature.

Alarm Monitor Circuits. Alarm monitor

When the oven is on (heating), the TDA OVEN indicator

2A12 controls the status indicators (TRAF, CARR IF,

(press-to-test) on meter panel assembly 2A15A2 lights

and SYNTH LOCK) on meter panel assembly 2A15A2.

white. Tunnel diode amplifier 2A2 provides 21.5 1.5

Monitor signals from 70 MHz intermediate frequency

dab gain in the frequency range 4.4 to 5.0 GHz at a

amplifier 2A5, af-rf amplifier 2A11 (and electrical

noise figure of 4.55 db maximum. The output of 2A2 is

frequency synthesizer 2A14 are applied to 2A12. For

applied to post selector .bandpass filter 2FLS.

normal operating conditions, the alarm monitor causes

the status indicators to light green. When an alarm

Post Selector Bandpass Filter 2FL5. Post

condition occurs (alarm monitor detected an abnormal

selector bandpass filter 2FL5 is a two-pole (two-cavity)

monitor signal), the circuits in alarm monitor 2A12 cause

bandpass filter that is set to the incoming rf frequency in

the associated status indicator to light red. Also, when

the 4.4 to 5.0 GHz band. In addition to passing the

any one of the alarm conditions occur, the alarm

desired rf signal, 2FL5 inhibits out-of-band and image

monitor activates the receiver summary alarm signal

frequency noise from tunnel diode amplifier 2A2 thereby

which is applied to Transmitter, Radio T-1054/GRC-144

maintaining the correct noise figure. Within 2FL5 tuning

and causes the ONTRL ALARM indicator on meter

cavities are ganged to a single frequency adjust control

panel assembly 1A1A8 to light red and an audible alarm

with direct readout dial of the frequency to which 2FL5 is

to sound.

set. The bandwidth of 2FL5 is nominally 30 MHz with a

maximum insertion loss of 0.85 db. The output of 2FL5

Metering Circuits. Signals from various

is applied to one input of amplifier-mixer 2A7.

assemblies in the R-1467/GRC-144 are monitored at

meter panel assembly 2A145A2. The metering circuits

Amplifier-Mixer 2A7. Amplifier-mixer 2A7

consist of a meter selector switch and a meter. A signal

converts the rf input signal to the 70 MHz if signal. The

is monitored by setting the meter selector switch to the

conversion is made by mixing the rf input signal (4.4 to

appropriate position. Meter calibration resistors are

5.0 GHz) with the local oscillator signal (4.3-5.07 GHz)

provided for certain meter indications. The meter circuit

which is 70 MHz above or below the rf input frequency.

also provides a test position which allows component

The output of amplifier-mixer 2A7 is applied to 70 MHz

test lead voltage monitoring.

bandpass filter 2A6.

Power Supply Circuits. Power supply 2A1

(1) Amplifier-mixer 2A7 consists of a crystal

produces regulated +28vdc, +15vdc, and -12vdc

voltages required to operate the circuits and indicators

mixer 2A7Z1 and three preamplifier stages, Q1 through

in Receiver, Radio R-1467/GRG-144.

Q3. The rf input signal is applied to one input of crystal

mixer 2A7Z1, and the local oscillator signal is applied to

2-20.

Function al Block Diagram Description of

the second input.

Receiver, Radio R-1467/GRC-144 RF Input

and Mixer Circuits (fig. 5-19)

(2) The rf input signal is mixed with the local

oscillator signal, to produce the 70 MHz difference

Preselector

Bandpass

Filter

2FL4.

frequency. The 70 MHz if frequency produced by

Preselector bandpass filter 2FL4 is a four-pole (four-

mixing the two signals appears at the output of crystal

cavity) bandpass filter that is set to the specific incoming

mixer 2A7Z1 and is amplified by preamplifier stages Q1

rf frequency in the 4.4 to 5.0 GHz band. The filter is

through Q3. The sum and difference signals from

directly at the input to the R-4467/GRC-144 and passes

2A7Z1 are also applied to negative and positive diode

only the desired rf signal to tunnel diode amplifier 2A2.

current monitor circuits for application to AMPILMIXER

Within 2FL4, each of the four tuning cavities is ganged

CURRENT 1 and AMPL-MIXER CURRENT 2 positions

to a single frequency adjust control dial with direct

of the meter selector switch on meter panel assembly

readout of the frequency to which FL1A is set. The

2A15A2. Potentiometers 2A7R22 and 2A7R23 provide

bandwidth of 2FL4 is nominally 25 MHz with a

proper metering of negative and positive crystal currents

maximum insertion loss of 0.65 db.

from 2A7Z1.

Tunnel Diode Amplifier 2A2. Tunnel diode

(3) IF ADJ control in the input circuit of first

amplifier 2A2 amplifies the rf signal (4.4-5.0 GHz) from

preamplifier stage Q1 is adjusted to produce an if

2F4A and provides a low noise figure. Tunnel diode

amplifier 2A2 consists of a tunnel diode assembly and

an oven assembly. The oven maintains the tunnel

2-47