4: 1650 kHz IF Board
PRC1099A-MS
4-3
4.1.3
Automatic Gain Control (AGC)
Automatic gain control monitors and adjusts the receive output signal to
insure it is not too large for an attached speaker. The AGC circuit taps the
receive line at the output of second receive IF amplifier Q2 and feeds that
output signal back to the input of first receive IF amplifier circuit Q7 on the
Mixer board. The AGC taps the output receive signal at variable step-down
transformer T4 and routes the sample to RF amplifier Q5.
RF Amplifier
AGC RF amplifier Q5 is an emitter-follower bipolar transistor. The low
impedance output drives the base of Q4 through voltage doubler rectifier D3
and D4.
DC Amplifier
AGC DC amplifier Q4 is a common emitter bipolar transistor with R18 as the
high impedance collector load. This gives a negative-going AGC output of 4V
to 0V. The AGC output controls the first 1650 kHz IF amplifier Q1 and
75 MHz IF amplifier Q7 on the Mixer board.
4.1.4
Specifications
Note:
These specifications are subject to change without notice or
obligation.
Table 4-1 1650 kHz IF Board Specifications
Characteristic
Specification
Transmit
Current
8 VDC at 4 mA
Output
1650 kHz, SSB
Input
1650 kHz, DSB
System Gain
14 dB
Receive
Current
8 VDC at 6 mA
Output
1650 kHz
Input
1650 kHz
System Gain
44 dB
AGC Range
55 dB
Filter
-6 dB
1647.3 to 1649.7 kHz
-60 dB
1646.0 to 1651.0 kHz