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Page Title: Function al Block Diagram Description of Receiver, Radio R-1467/GRC-144 RF Input and Mixer Circuits
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TM 11-5820-695-35
diode assembly above a predetermined temperature.
f.
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
c.
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
g.
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
d.
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.
h.
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
a.
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.
b.
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


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