PRC1099A-MS
3-1
Chapter 3: Audio/Filter Board
3.1
Circuit Description
The Audio/Filter board includes the transmit and receive RF filtering,
transmit/receive (T/R) switching, audio modulation and demodulation, and
other control functions. The following sections discuss the components of the
block diagram as shown in Figure 4-1.
Figure 3-1 Audio/Filter Board Block Diagram
1650 kHz IN
1650 kHz
1647 kHz
1650 kHz
DSB OUT
Gain
Adjust
to the
front panel
Accessory
connector
Microphone
ALC
Voice
Detect
K13
T/R Relay
PTT
Product
Detector
Audio
Amplifier
Gate
Audio
Amplifier
600 ohms
Balanced
Modulator
VOGAD
Sidetone
Switch
CW Hold
Timer/Gates
Squelch
Circuit
RX IN
J9
BFO IN
J7
TX OUT
J10
RX OUT
J8
High Pass
Filter
K13
T/R
Relay
from the
Power
Amplifier
board
Low Pass Filters
Low Power
Control
(5W)
1.6-30 MHz
2.0–2.99999 MHz
ALC
Detectors
Relay Drivers
and
Serial Decoder
Low Power
Switch
(5W)
3.0–4-99999 MHz
20.0–30.0MHz
13.0–19.99999MHz
8.0–12.99999 MHz
5.0–7.99999 MHz
SPI DATA
SPI CLK
RF OUT
J12
RF IN
J11
+12V
RF Detect
Squelch
Circuit
CW
Oscillator
Display
Contrast
Control
Contrast
Control
T8
R8
+8V
K13
T/R Relay
from the
1650 kHz
board
from the
Synthesizer
board
to the
1650 kHz
board
to the
Antenna
Tuner
board
from the
Processor
board
to the
Display
board
from the
Mixer
board
to the
Processor
board
from the
front panel
Audio connector
from the
Processor
board