R.V.R. Elettronica PTRL-NV/S3, Technical Manual

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R.V.R. ELETTRONICA S.r.l. (BO) Pag. 15
PTRLNV/S3 - Technical and Maintenance Manual
CHAPTER 2
ELECTRICAL DESCRIPTION
2.1 INTRODUCTION
This section describes, in detail, the operating theory of the
PTRLNV/S3. To aid understanding, the unit has been subdivided into
blocks, each of which is fully described below. A block diagram is shown
in Fig.3.
2.2 POWER SUPPLY
This sub-assembly comprises 2 board mounted on heat-skins, in turn
mounted at right-angles to each other on the chassis base (Photo 1-2).
The power supply generates the stabilized voltages required by the
various modules comprising the PTRLNV/S3. After having undergone
filtering for mains-borne interference, the supply is transformed to
lower voltages, rectified, smoothed and stabilised for the following
outputs: +5V, +12V, +15V, -15V and 2-18 V variable. The +5V output
supplies the CPU card, the ±15V outputs supply the Main card, the CPU
card, the coder mixer, the Modmeter card and the Anameter cards 1 and
2; the +12V output supplies the final power stage of the transmitter.
The voltage aplied to the final stage is varied by the PWR ADJ control.
An automatic output power limiting system intervenes in the case of excess
S.W.R. on the R.F. output. All supply voltages and the current drawn by
the final stage may be monitored by the analog multimeter.
2.3 AUDIO INPUT CARD
This card is situated on the rear panel of the transmitter (see
Photo 1-2).
The card filters all audio signal inputs to the unit incoming from the
outside world, removing RF interference, before supplying them to the
encoder mixer.
The main operating parameters of the transmitter are available for remote
monitoring via a 9-pin D-type serial connector.
2.4 CODER MIXER
This board is placed underneath the internal chassis (see photo 2).
The card can function either as a stereo encoder or as a simple mixer
for the various audio inputs.
The function may be selected by a control situated on the front panel.
In stereo encoder mode, the 19 KHz pilot tone is derived from a quartz
crystal reference oscillator. So too is the sampling frequency which
allows the L and R signals to be separated from the multiplexed signal,
plus the suppression of the 38 KHz frequency.