PRC1099A-MS
4-1
Chapter 4: 1650 kHz IF Board
4.1
Circuit Description
The 1650 kHz IF board includes a SSB filter included in both the transmit and
receive signal paths with separate amplifiers for each mode. The AGC system is
generated in this board. The following sections discuss the components of the
block diagram in Figure 4-6.
4.1.1
Transmit Path
In the transmit signal path, the 1650 kHz IF board receives the transmit signal
from the Audio/Filter board on coax connector J2 (TX IN). It is then applied to
1650 kHz transmit amplifier Q3.
1650 kHz TX
Amplifier
Transmit IF amplifier Q3 amplifies the low-level, dual sideband signal from the
balanced modulator on the Audio/Filter board. It also provides correct matching
to the 1650 kHz sideband filter.
1650 kHz
Crystal
Sideband
Filter
The 1650 kHz crystal sideband filter consists of six crystal filters. In transmit
mode, the 1650 kHz sideband filter removes one of the sidebands from the
double-sideband suppressed carrier signal generated by the balanced modulator
on the Audio/Filter board.
Figure 4-1 1650 kHz IF Board Block Diagram
1650 kHz
from
Mixer Board
(TX Out/RX In)
TX In
from
Audio Board
(1650 kHz)
To
Mixer Board
(75MHz)
RX Out
to Audio Board
1650 kHz
1650 kHz
SSB Filter
1647.3 to 1649.7 kHz
TX
IF Amp
RX
IF Amp
AGC
Amp
AGC
Amp
RX
IF Amp