User's Manual

The V C O comprises T321,C oil L320,and varactor D 303 D 302.D303、D302 produces a change in
frequency with a change in D C voltage and is controlled by the tuning voltage signal present at
the cathode.The local oscillator programmable dividers.DATA is received by U401 at pin 12 from
pin 13 of U401.
The R F signal at the collector of T321 is applied to an amplifier/ buffer T322.The amplified S ignal
from T322 passes to the prescaler,U401 pin5.The R F signal at the collector of T321 also Drives
the cascode amplifier/ buffer formed by T322 and T341.
When D 341 is forward biased (TX ON),carrier frequencies at the collector of T341 pass to the
Power amplifier and harmonic filter.When D 342 is forward biased (RX ),local oscillator
F requencies at the collector of T341 pass to the first mixer (T202).
PL L IC
The reference frequency from the V C TC X O,at 12.8 MHZ,is connected to pin 8 of U401(LMX 2332
ATM)The appropriate V C O is connected to pin 13.
R E F DIV divides the 12.8 MHZ to produce a reference frequency (F r) of 5 or 6.25 k Hz dependent
upon channel spacing selected.V AR D IV divides the prescaled V C O frequency to produce a
variable frequency(F v).F v and F r are fed to the phase detector.
Phase detector
When F v=F r,the phase detector output (pins 3 and 18,U401)produces narrow negative pulses
And F v and F r pulse widths are identical.The signal at pin 3 and 18 is smoothed the loop filter
and applied to the V C O.
Out-of-lock detector
The out-of-lock detector produces a series of logic level pulses when the loop is out of lock at pin
10 of U401.
C harge Pump and Loop F ilter
Associated resistors and capacitors form the charge pump and loop F ilter.The phase detector
output from U401 pins 3 by the charge pump to Produce a 0 to 5v tuning voltage signal.