Sharp Linytron C-1408T Serviceanleitung Seite 9

| = G-1408T
AUDIO MUTING CIRCUIT
[1] Tuner
The IF signal is further sent to the IF amplifier and appears
Fig. 8 is a block diagram of the tuner and the arrow marks
at the IF output terminal of the tuner. AFT terminal is
in it show the signal transfer in the tuner. The UHF/VHE
provided and it controls the local oscillation frequencies to
signal from the antenna is first filtered for DC cutting and
prevent the tuner's IF signal from being detuned.
is fed into the RF amplifier. The VHF signal from the low-
See Fig. 9, 10. for the voltage characteristics of each ter- .
pass filter is sent to the VHF RF amplifier, and the UHF
minal.
signal from the high-pass filter enters the UHF RF ampli-
The features of this tuner are:
fier. The selected channel signal is amplified with the band
@ Very compact (as small as 33 cc in volume)
switch (V1, VII and U) and Vr (tuning voltage) supply,
@ Chip IC included
then is delivered to the mixer. It is in the mixer that UHF
e AFT provided
or VHF signal is made together with the signal coming from
@ Transistor mixer is used as UHF mixer: Compared with
the local oscillator that oscillates at the specified frequency
the conventional diode mixer, it offers the better tuning
across the Vr, which results in IF signal.
selectivity.
75 ohm
UHF BLOCK
VHF BLOCK
¢ baht Kee
at
Low-Pass
Figure 8. Tuner Block Diagram