R.V.R. Elettronica PTRL-NV/2/S3, Техническое руководство

Страница: 15 / 162

R.V.R. ELETTRONICA S.r.l. (BO) Pag. 15
PTRLNV/2/S3 and PTRL-NV/2/HP/S3 - Technical and Maintenance Manual
CHAPTER 2
ELECTRICAL DESCRIPTION
2.1 INTRODUCTION
This section describes, in detail, the operating theory of the
PTRLNV/2/S3 (and PTRL-NV/2/HP/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/2/S3 (and PTRL-NV/2/HP/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