Yaesu FT-7100M, Technical Supplement

Page: 5 / 68

5
Circuit Description
VHF Reception
Incoming VHF signals are passed through a low-pass
filter network, antenna switching diodes D1056 ( 1SS355 )
and D1057 ( RLS135 ), and a high-pass filter network, and
on to the RF amplifier Q1007 ( 3SK131 ). The amplified
RF signal is passed through another RF amplifier Q1011
( 2SC5226 ) and band-pass filtered again by varactor-tuned
resonators L1022, L1029, L1034 and D1009 , D1012 , D1014
(all HVU359 ), then applied to the 1st mixer Q1023
( 3SK228 ) along with the first local signal from the PLL
circuit.
The first local signal is generated between 122.3 MHz
and 126.3 MHz by the VHF VCO, which consists of Q1025
( 2SC5006 ) and varactor diodes D1023 , D1024 , and D1066
(all HSV362 ) according to the receiving frequency.
The 21.7 MHz first IF signal is applied to monolithic
crystal filters XF1003 and XF1004 (both 21R12B5 ) which
strip away unwanted mixer products, and the IF signal is
applied to the first IF amplifier
Q1032 ( 2SC4400 ). The
amplified first IF signal is then delivered to the FM IF sub-
system IC
Q1043 ( TK10931V ), which contains the second
mixer, limiter amplifier, noise amplifier, and FM detec-
tor.
The second local signal is generated by 21.25 MHz crys-
tal X1002 and Q1060 ( 2SC5374 ), producing the 450 kHz
second IF signal when mixed with the first IF signal with-
in Q1043.
The 450 kHz second IF signal is applied to the ceramic
filter CF1002 ( ALFYM450F ) which strips away all but the
desired signal, and then passes through the limiter am-
plifier within Q1043 to the ceramic discriminator
CD1002
( CDBM450C7 ), which removes any amplitude variations
in the 450 kHz IF signal before detection of speech.
The detected audio passes through the de-emphasis
network, a high-pass filter consisting of Q1088
( NJM2902V-3 ) and associated circuitry, and a low-pass
filter consisting of Q1088 ( NJM2902V-4 ) and associated
circuitry. The filtered audio signal is amplified by Q1047
( NJM2902V-1 ), then passes through the audio volume
control IC Q1096 ( M511312FP ) which adjusts the audio
sensitivity to compensate for audio level variations, and
then is delivered to audio switch
Q1094 ( BU4053BCFV ).
When the internal speaker is selected, the audio signal
is amplified by Q1098 ( TDA7233D ), then applied to the
internal loudspeaker. When the external speaker is select-
ed, the audio signal is amplified by
Q1097 ( TDA2003H ),
then it passes through the EXT SP jack to the external loud-
speaker.
UHF Reception
Incoming UHF signals are passed through a low-pass
filter network, high-pass filter network, antenna switch-
ing diodes
D1058 ( 1SS355 ) and D1059 ( RLS135 ), and
on to the band-pass filter network consisting of varactor
diode
D1004 ( HVU359 ) and L1001.
The filtered UHF signal is amplified by RF amplifier
Q1008 ( 3SK228 ) and fed to another band-pass filter con-
sisting of varactor diode D1006 ( HVU359 ) and L1008, and
then is passed through another RF amplifier Q1010
( 2SC5226 ) to another band-pass filter consisting of var-
actor diodes D1010 and D1011 (both HVU359 ) and L1027/
L1030.
The amplified and filtered UHF signal is applied to
the 1st mixer Q1019 ( 3SK228 ) along with the first local
signal from the PLL circuit.
The first local signal is generated between 384.95 MHz
and 404.95 MHz by the UHF VCO, which consists of
Q1024 ( 2SC5006 ) and varactor diodes D1020 ( 1SV281 )
and D1021 ( 1SV280 ), according to the receiving frequen-
cy.
The 45.05 MHz first IF signal is applied to monolithic
crystal filters XF1001 and XF1002 (both 45M15B5H )
which strip away unwanted mixer products, and the IF
signal is applied to the first IF amplifier
Q1029 ( 2SC4400 ).
The amplified first IF signal is then delivered to the FM IF
subsystem IC
Q1034 ( TA31136FN ), which contains the
second mixer, limiter amplifier, noise amplifier, and FM
detector.
The second local signal is generated by 45.505 MHz
crystal X1001 , producing the 455 kHz second IF signal
when mixed with the first IF signal within Q1034 .
The 455 kHz second IF signal is applied to the ceramic
filter CF1001 ( CFW455F ) which strips away all but the
desired signal, and then passes through the limiter am-
plifier within
Q1034 to the ceramic discriminator CD1001
( CDBM455C7 ), which removes any amplitude variations
in the 455 kHz IF signal before detection of speech.