 |
|||
|
|
|||
|
Page Title:
Frequency Converters |
|
||
| ||||||||||
|
|  TM
11-5820-919-40-1
antenna tuner applies a Tune In Progress
ALC In (Figure 2-7).
2-91.
In the
audio control hybrid A4, the ALC In is
signal to the ALC time constant switch.
routed to the ALC Off/On.
The reference
voltage from the ALC offset adjust deter-
2-92.
PA OFF/ON Control.
mines the threshold at the ALC amplifier.
describes the PA OFF/ON control logic.
The time constant of the ALC amplifier
The PA OFF/ON control is used with other
output is adjusted by the ALC time con-
configurations of the receiver/ exciter,
but not the AN/PRC-104.
stant switch.
This occurs when the
PA
OFF/ON
CONTROL
LOGIC
Input
+6.5v
Transmit
Enable
PA
OFF/ON
Control
Result
1
ON
- (3.5 ma)
0
OFF - (0 ma)
Frequent y
Receive Audio becomes the To Vol Control
signal which is fed back to the audio
2-94.
In transmit
control hybrid to control the output of
Third Converter A3.
operation, relays K1 and K2 are ener-
the receive audio amplifier.
In data
gized by the +28v Xmt Enable and by the
mode, a 100-microfarad capacitor is
Keyline ground signal.
This permits the
switched out, which shortens the time
constant on the agc generator output.
Xmt Audio to be mixed with the 5-MHz LO
(amplified by Q1) at mixer U4 via the
Finally, the 5-MHz if. mixes with the
energized contacts (3-2) of K2.
The 5-
5-MHz LO to create the audio frequency
MHz mixing product goes to the sideband
and upper sideband mixing product at
filter FL2 via the energized contacts
mixer U4.
(7-8) of relay K2 and contacts (7-8) of
relay K1. The energized contacts (2-3)
2-95.
Sideband Filter FL2.
The crystal
of relay K1 also route +12.5v to the
filter functions identically in receive
first converter.
The +12.5v Xmt also
and transmit operation.
The filter
turns switch Q6 on, which causes +6.5v
rejects frequencies other than 4.9970
Xmt to be applied to the second con-
to 409997 MHz.
verter A2 and the audio control hybrid,
A4.
In receive operation, the relays
are not energized so the 5-MHz if. goes
2-96.
In transmit
Second Converter.
through amplifiers U1 and U2 and +12.5v
operation, relay K1 is energized by the
is applied to Zener diode VR1 (which
+28v Xmt Enable and by the Keyline sig-
breaks down at +6.5v). The gain of the
nal.
The 5-MHz if. goes through match-
5-MHz if. is controlled at U2 and U1 by
ing transformer T1 and to amplifier U2;
the agc voltage from the agc generator
the level (amplitude) of the entire
U3. This agc voltage is also applied to
modulator/demodulator transmit output
the second frequency converter via FET
is controlled at this amplifier by the
Q7; FET Q7 conducts when the +12.5v Xmt
ALC signal from the audio control hybrid
enable is absent at the gate (G). The
A4 and by the presence of the +6.5 Xmt
agc generator, in turn, is controlled by
The 5-MHz if. is applied
Enable signal.
the Rcv agc receive audio signal from
to mixer U4 where it mixes with the
the audio hybrid.
A portion of the agc
70/80 MHz LO. (The 70/80-MHz Lo has
|
|
Privacy Statement - Press Release - Copyright Information. - Contact Us |
Click
here for thousands of PDF manuals