R.V.R. Elettronica TEX20-NV, Technical Manual

Page: 17 / 110

TEX20-NV Technical and Maintenance Manual
R.V.R. Elettronica S.r.l. (Bo) Pag. 17
the selected operating frequency.
This signal is amplified to drive the phase-locked loop (PLL) control circuit
and also the final stage.
The audio signal supplied by the Euro Audio Input card (for the EUROPA version)
or from USA Audio Input card (for USA version), is amplified and processed
in order to compensate for distortion caused by the varicap diodes; it is then
injected into the VCO to provide modulation.
The operating frequency generated by the VCO is divided down before being
compared to a reference frequency, generated by a high stability oscillator
(standard 5 ppm). The error voltage is filtered and used to compensate the
VCO frequency and guarantees its stability.
An indicator (situated on the front panel signals the "unlocked" condition.
Three trimmers are present on this card for adjustment of deviation, distortion
and pre-polarization of the varicaps.
2.5 R.F. POWER AMPLIFIER
The final power stage is mounted on a heat sink to dissipate waste heat
and is enclosed in a totally screened, metal container, fixed to the middle
part of the unit’s bottom (6 Foto 1-2).
The R.F. signal coming from the Main card at a power level of about 150-200
mW, reaches the driver stage (MRF237 in Class C) and is amplified to a level
of about 2W before being further amplified by the final stage (BLW86) to a
level of upto 20W.
The resultant signal is then filtered by a low-pass filter which removes any
harmonic content.
A directional coupler allows the direct and reflected power levels to be
measured and displayed on the analog multimeter and also feedback to the power
supply for automatic control of the output power (see Power Supply sec. 2.2).
A BNC connector situated on the rear panel provides a power signal at -30dB
of the amplifier output power.
2.6 FREQUENCY SELECTOR CARD (CONTRAVES)
This card (3 Foto 1-2) is fixed to the left-hand side of the front panel.
The operating frequency selected by the frequency control is represented by
a signal which is supplied to the frequency dividers that form part of the
PLL circuits found on the Main card.
2.7 USA AUDIO INPUT CARD (only for USA version)
This card is situated on the left part of the rear panel of the exciter
(7 Foto 1-2).
This card, only for USA version, filters all audio signals that input to the
unit, removing RF interference, before supplying them to the main card.
In addition to three SCA input connectors and MPX input connector, there is
a 10 poles socket that .