Icom IC-R7000 Service Manual page 12

(c) BPF3
Receive signals via 019 are fed to a HPF consisting
of L32, L69, C34, C35, C51 and C133. The cut-off
frequency of the HPF is 240 MHz.
The receive signals are then input to the RF amplifier.
The input tuning circuit of the RF amplifier (Q3) is
composed of 021, 022, L33 and L34. The output
tuning circuit is composed of 023, 024, L36 and L37.
These circuits are tuned by the tuning voltage from
IC2(A).
(d) BPF4
Receive signals via RL 1 are fed to the parallel
resonance circuit consisting of varicap 026, L39 and
C45. The circuits attenuate interference signals to
half of the receive frequency.
Input and output tuning circuits of the RF amplifer
are composed of a strip line and varicaps 027-030.
By utilizing the strip line, stable operations are main-
tained at high frequencies.
These circuits are tuned by the tuning voltage from
IC2(B).
4-1-4 RF AMPLIFIER (RF UNIT)
Signals from BPF are then applied to wide frequency
band amplifier Q7 with a gain of approximately 10dB.
4·1·5 LO TRAP (TUNED NOTCH) CIRCUIT (RF UNIT)
The LO trap circuit consisting of a strip line and
031-034 prevents the 1st LO signal leakage to the
ANTENNA CONNECTOR.
The notch frequency is controlled by a control voltage
from IC3(B), matching the 1st LO frequency.
A LPF consisting of a strip line and C78, C82, C89
and C137 attenuates higher harmonics of the 1st LO
signal.
4·1·6 1sr LO AND 1sr MIXER CIRCUITS (RF UNIT)
A BPF consisting of a strip line, L78, C134, C59, C77
and C53-C55 attenuates unnecessary signals from
the PLL UNIT.
Table 2 shows the relation among receive frequencies
(FRX) and 1st LO frequencies (F1s1Lo).
RECEIVE FREQUENCY 1st LO FREQUENCY
FRX [MHz] F1stLo[MHz]
25- 89.9999
803. 7- 868.6999
1025-1089.9999
90- 249.9999
868.7-1028.6999'
1090-1249.9999
250- 519.9999
1028.7-1290.6999
1250-1519.9999
512- 999.9999
778.7-1266.6999
1512-1999.9999
Table 2
4-2
Q5 and Q6 amplify the 1st LO signal from the PLL
UNIT to approximately 10dBm. The output of Q6 is
applied to IC6.
A DBM (double-balanced mixer) IC6 converts receive
signals to 1st IF (778.7MHz or 266.7MHz) signals.
4·1·7 1sr IF CIRCUIT (RF UNIT)
(a) 1st IF AMPLIFIER
1st IF signals from IC6 are amplified at QB and they
are applied to Fl1 or Fl2.
Table 3 shows the relation among receive frequencies
(FRx) and 1st IF frequencies (F1st1F)·
RECEIVE FREQUENCY 1st IF
FRX [MHz] F1s11F[MHz]
25- 89.9999
778.7 (Fl1)
1025-1089.9999
90- 249.9999
778.7 (Fl1)
1090-1249.9999
250- 519.9999
778.7 (Fl1)
1250-1519.9999
512- 999.9999
266.7 (Fl2)
1512-1999.9999
Table 3
(b) Fl1 CIRCUIT
The F11 circuit is a BPF with a center frequency of
the passband at 778.7MHz and a pass-bandwidth
of 5MHz. The image interference signal (757.3MHz)
is attenuated by a notch filter consisting of L51, and
C79.
(c) Fl2 CIRCUIT
The F12 circuit is a BPF with a center frequency of
the passband at 266.7MHz and a pass-bandwidth
of 5MHz. The image interference signal (245.3MHz)
is attenuated by a notch filter consisting of L67, L68,
and C88. Series resonance circuits consisting of
L73, C86, L74, and C90 sufficiently attenuate off·
band signals.
1st IF signals from the Fl1 or Fl2 circuits pass through
a LPF consisting of a strip line and C139-C141. 1st
IF signals are then fed to IC7.
4·1·8 2No MIXER CIRCUIT (RF UNIT)
The 2nd LO signal (256MHz or 768MHz) from the PLL
UNIT is fed to a LPF consisting of a strip line, C104,
C105, and C146. The 2nd LO signal is amplified by
Q16 and Q17 to approximately 10dBm, and is then fed
to a 3dB attenuater (ATT) consisting of R116-R118.
Table 4 shows the relation among receive frequencies
(FRx) and 2nd LO frequencies (F2nd Lo).