R.V.R. Elettronica URP, Техническое руководство

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URP Technical and Maintenance Manual
R.V.R. Elettronica S.r.l. (Bo) Pag. 13
CHAPTER 2
ELECTRICAL DESCRIPTION
2.1 FRONT PANEL BOARD
The front panel board contains all of the controls, switches and
indicators necessary to operate the unit.
Toggle switches control DC power (9 Fig.1), RF power (3 Fig.1),
Stereo /Mono selection (1 Fig.1), Line/Mike selection (2 Fig.1), and
Power/Deviation selection.
The four digi-switches (5 Fig.1) control the frequency of the unit in
100KHz steps.
2.2 SYNTHESIZER BOARD
The Synthesizer board contains the phase lock loop circuits required
to maintain the unit on frequency. IC1 is the reference frequency
oscillator and divider.
The crystal oscillator oscillates at 6.4MHz and is divided down to
781.25Hz which is the reference input frequency to IC2 phase detector.
The VCO frequency of 88 to 108MHz comes in to the board at CN7 to IC4
where it is divided by 128.
The VCO signal then goes to T2 and IC5. IC5 divides by a number determined
by the front panel digi-switches. The output of this divider is 781.25Hz
when the units is locked to the reference frequency.
When the unit is out of lock the phase detector generates an error signal
which if filtered by IC3B and used to steer the VCO to the proper
frequency.
IC3A generates the Mute signal which shuts down the RF output when the
unit is unlocked, and lights the unlock light (12 Fig.1) on the front
panel.
2.3 VCO/AUDIO BOARD
The VCO/Audio board generates an RF signal at the output frequency
which is locked to a stable crystal reference as shown in 2.2.
The VCO is T4 and its associated circuits. The coil L1 is made up of coaxial
cable to prevent microphonics in the output signal due to vibration of
the oscillator components.
Diodes D2 and D4 are varicap diodes used to control the frequency of the
VCO.
A DC control voltage from the synthesizer is used to control this point.
Diodes D1 and D3 are used to modulate the VCO with the desired audio signal
from the audio processing circuits.
T6 and T7 make up a set of gate controlled amplifiers. T9 controls the
on/off condition the amplifier by application of the unlock control
signal from the synthesizer.
The Audio section process the input audio signal for application to the