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5.5.8.
5.5.9.
A
VC03
This circuit bciard contains the loop 3 I ilter and the voltage con-
trolled oscillator VC03.
The loop 3 filter cc]nsiscs of a low-pass i ilter alid an int:egrator.
The filter serves to remove the pulses of the phase/freq. detector
output signal and allow only the DC infomation Co pass oa to the
vari-cap diodes of VC03. By use of the phase error adjustment the
phase error pulse width can be minimized, and once adjusted it Will
remin unchanged throughout the whole frequeocy ralige of VC03 due
to the use of an integrator in the loop filter.
:::3v:8:: ;9::c:fc:::::n:a:t:::dc::t::;:::£=:::;a:8rfa:f°#: :::3y
selection is carried out by trean8 of a decoding circuit otl
303 .
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A
Master Oscillator (0
tional)
The oscillator itself is a Sealed unit cont:aiming a highly stable
TCXO (temperature conpen§ated crystal oscillator) at 11.2 rmz. The
output signal of the TCXO is anplif led in the transistors TRl to
TR3 and fed co the binary counter Icl which divides the input f re-
quenc:y by 8. The 1.4 rmlz square wave signal is filtered ill a tuned
circuit C6, T1, and the regulting sine Have signal is fed to the
outpiit teminals.
TCXO'8
of
two different tnanufactures may be used. In both cases
crystal oscillator aging is very s"11 (less than 10-6 per ann`m)
and will be greatest during the f ir§t fen years. Aging rill nomally
cause an increase in f requency which in one case can be compensated
for by introducing the connection indicated by the dotted line in
the circuit diagram (this will reduce the frequeacy by approx.
2xl0-6) and in the other case by changing tbe fac:tory Selected re-
sistor. The resistor should be selected at 25°C achient teaperature
to give a TCX0 output f requency of i get frou the nominal frequency
(11.2 l"z) by the anoimt tnarked on the can.
Frequency adjustmetit should be carried out otlly i£
courlter is available for control of the frequency.
sured that the accuracy of the counter a[ the I
than 10-7.
5.5.1o. E
and Ke
board
quality
Dust be en-
is better
When a key is
pressed
or released sotne sort of bouncing e££ect
Will always appear before the key has settled. This bo`mcing i8 re-
moved by means of the Key Bounce Elirinator con3igting o£ IC45 and its
associated external coxponent8. When a key has Settled after being
pressed,
a read-pulse is produced at pin 12 of IC45 and the BCD
code of the key tiunl)er in question ia produced by IC46 and IC47.
B:::::::tt::°:e:::::::et:: :a¥:: ::yt#.I i:a:nr:::5:=e;n°:h:u§::
register stack IC42 or to the first register in the frequency digit
register stack |C41. The BCD code is at hand on the input cif botb
register Stacks. The directioa of the read-pulse fron IC45 and the
5-8
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