Alinco DR-620, Руководство по обслуживанию

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) UHF Reception
Incoming UHF signals are passed through a low-pass filter network, high-pass filter network, antenna
switching diodes D16 (1SS355) and D18 (1SV268), and on to the band-pass filter network consisting
of varctor diode D49 (HVU359) and L79.
The filtered UHF signal is amplified by RF amplifier Q41 (3SK240) and fed to another band-pass filter
consisting of varactor diode D50 (HVU359) and L80, and then is passed through another RF amplifier
Q43 (2SC5226) to another band-pass filter consisting of varactor diodes D51 and D52 (both HVU359)
and L81/L82.
The amplified and filtered UHF signal is applied to the 1st mixer Q42 (3SK240) along with the first local
signal from the PLL circuit.
The first local signal is generated between 384.9 MHz and 404.9 (*2) MHz by the UHF VCO, which
consists of Q29 (2SK508) and varactor diodes D38 and D40 (both ISV278), according to the receiving
frequency.
The 45.1MHz first IF signal is applied to monolithic crystal filters XF3A and XF3B (Q4511BD10) which
strip away unwanted mixer products, and the IF signal is applied to the first IF amplifier Q44 (2SC4618).
The amplified first IF signal is then delivered to the FM IF subsystem IC IC5 (TA31136FN), which 2)
The amplified first IF signal is then delivered to the FM IF subsystem IC IC5 (TA31136FN), which
contains the second mixer, limiter amplifier, noise amplifier, and FM detector.
The second local signal is generated by 45.555 MHz crystal X4, producing the 455 kHz second IF
signal within IC5.
The 455kHz second IF signal is applied to the ceramic filter FL4 (CFW455E) which strips away all but
the desired signal, and then passes through the limiter amplifier within IC5 to the discriminator coil
L102 , which removes any amplitude variations in the 455 kHz IF signal before detection of speech.
The detected audio then signal is amplified by IC9 (NJM2902V-C) passes through the de-emphasis
network, a high-pass filter consisting of IC9 (NJM2902V-D) and associated circuitry, and a low-pass
filter consisting and associated circuitry. The filtered audio signal is switched by IC12 (BU4052), then
passes through the audio volume control IC IC13 (M511312FP), which adjusts the audio sensitivity to
compensate for audio level variations.
The audio signal is amplified by IC8 (LA4425A) then applied to the internal loudspeaker.
3) FM Reception
Incoming FM signals are passed through a low-pass filter network, antenna switching diodes D19
(1SS355), D20 (1SV2685) and D26 (DAN235E), and a high-pass filter network, and on the RF amplifier
Q36 (2SC5066). The amplified RF signal is passed through band-pass filtered L, C, then applied to
the 1st mixer Q33 (2SC5066) along with the first local signal from the circuit.
The first local signal is generated between 86.7 MH and 118.7 MHz by the FM VCO, which consists of
Q14 (2SC4808) and varactor diodes D23, and D25, (both 1SV282) according to the receiving frequency.
The 10.7 MHz first IF signal is applied to ceramic filters FL3 (SFT10.7MAS) which strip away unwanted
mixer products, and the IF signal is applied to the first IF amplifier Q37 (2SC4618). The amplified first
IF signal is then delivered to the FM IF subsystem IC IC3 (TK10931V), limiter amplifier, noise amplifier,
and FM detector.
The 10.7 MHz first IF signal is applied to the discriminator coil L53, which removes any amplitude
variations in the 10.7 MHz IF signal before detection of speech.
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