Rf Unit - Icom IC-7300 Service Manual

3-2 RF UNIT

The RF UNIT is composed of the receive and transmit RF circuits.
The received signal from the PA UNIT is passed to the MAIN
UNIT through the attenuator, fi lter, and preamp.
The transmit signal from the MAIN UNIT is passed to the PA
UNIT through the fi lter, ALC circuit, and YGR AMP.
(1) RECEIVE SIGNAL PROCESSING
The received signal from the PA UNIT is passed through
the RX mute switch (D1001), passes through or bypasses
the attenuator (D1081 ~ D1083) according to the Attenuator
function setting, and is then applied to the fi lter circuit. The
attenuator (D1081 ~ D1083) is controlled to change the at-
tenuation level to between 0 dB (bypass) and 20 dB.
The fi lter circuit is composed of 15 fi lters. The received signal
is passed through the fi lter that is selected according to the
receive frequency.
• RF UNIT (Receive circuits)
D1081~D1083
ATT
D1001
MUTE
To the TX AMP
TX signal
RX signal
HPF A
1.60-74.80 MHz 1.60-30.00 MHz
HPF LPF
The received signals of 1.6 MHz and below are passed
through only "LPF (A)." The received signals of 1.6 MHz and
above are passed through "HPF (A)," which is designed to
prevent interference by strong MF band broadcast stations.
This HPF is designed to obtain more than 20 dB of isolation
for 1.6 MHz and lower frequencies. The received signals of
1.6 MHz and above are also passed through one of the BPFs,
according to the selected operating band.
The fi ltered signal is then applied to the preamp circuit. The
received signal may be amplifi ed by P.AMP1 (normal gain) or
P.AMP2 (higher gain), or bypass both, according to the Pre-
amp function setting. The received signal from the preamp
circuit is then applied to the MAIN UNIT.
LPF A
0.03-1.59 MHz
LPF
1.60-1.99 MHz 15.00-21.99 MHz
BPF
2.00-2.99 MHz 22.00-29.99 MHz
BPF
30.00-49.99 MHz
3.00-4.49 MHz 54.01-69.99 MHz
BPF
4.50-6.49 MHz 50.00-54.00 MHz
BPF
6.50-7.99 MHz 70.00-74.80 MHz
BPF
8.00-9.99 MHz
BPF
10.00-14.99 MHz
BPF
3-2
Q1211
Q1212/Q1213
PRE
AMP
BPF
BPF
RF UNIT
BPF
BPF
BPF
RF