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The 38 to 0-30 rmz mixer 302 IC7 is a double balanced passive mixer
converting the signal co the transmitting frequency by mixing i[
uith the injection frequency from the VC03. The signal is anplified
in TR5 before the image signal is removed in the 7th order low-pass
filter. The desired signal is amplified [o FULL power level in TR9.
Before the signal leaves the board, it passes the stepattenuator con-
trolled by the POWER suitch setting or remote control interface.
The attenuator is a nodif led T-attenuator attenuating OdB, 6dB and
approx. 12dB.
=:p;;fi::e:i: :::q£:C:x::t:i4 ffi i:nrt;:f;::6 £hi:h3c3?f£: g±
£erence frequency is derived from the TCX0 in order Co accomplish
the necessary degree of frequency scabilicy of the output signal
from the voltage controlled oscillators
The 1.4 MHz reference frequency is divided by seven in the divider
IC3 before it-as a 200kllz signal -is fed to one of the input ports
of the Phase Detector IC5. The output from the 36.6 rmz VC0 is buf-
fered up through TR13, TR14, TR7 ar`d half of IC6 before it is di-
vided by 183 in the synchronous divider consisting of IC9 and IC8
and the other half o£ IC6 which acts as presetting control.
The output of the VC0 is amplitude regulated and fed to the 1.4 rmz
to 38 MHz mixer IC1.
The selection of the variable resistor for the level settiag i8 carried
out
by
the
band decoders IC2 and IC4 turning the diodes I)1 to
I)17 (except D6) on and of f .
5.5.4.
A
Control Circuit and Tone Generators
The mode control signals from the MODE §uitch, the A3H §ixplex sig[lal
from the frequericy memory in E and the RE infornatioo fron the
transmitter power anplif ier are the input signals to the programable
read only nenory (PROM), IC5, of the Mode Selector. The PRon has been
Programed to give at the output the desired control sigtlals correspon-
ding to the Wanted mode.
£et=d:. :eE:t::c::::rodih:i:n::: :::;::::v:a:a:::o¥::a:::I;a:
1.5 kHz SHIFT output tells. when HIGH, tbe syathesizer to decrease
its frequency by I.5 kHz. In the Fl trade the anode voltage of the
P.A. valves is lowered by nears of a relay in the poser pack controlled
from transistor TR5. Automatic selectioa of FULL POWER is carried
out by means of transistor TR4, when A3H sixplex (ceminal 14a Low)
:::t¥u¥::efL#t£:::P::e°ie;f a:::c::¥: are Selected. The tcode se-
Keying of the transmitter is only possible from the roRSE FEY input
in the A2H and Al nodes, £ron the TELEX FEY irxput in the Fl mode,
from the HANDSET KEY input in the A3A, A3J, A3H and TBANsmT AIARH
mdes, and from the DUPLEX input in the F1, A3A, A3J, ASH or TRANSHT
AI.ARM nodes, provided A3H 8ixplex i8 not selected as the DUPLEX input
is then inhibited. Furthemore the infortnacioti on terminal 24a (rm)
has to be in accordance with the node Selected: HIGH a[ A2tl, Al and
:1o'n ::Wt:: =36. =J;h:3: ::n=s=u:p=. t=isin:: g8:: by co-ec-
5-5
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