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

Page: 43 / 171

R.V.R. ELETTRONICA S.r.l. (BO) Pag. 41
PTRLNV/S3 - Technical and Maintenance Manual
5.7 CALIBRATION OF THE VCO
To calibrate the VCO, carry out the following procedure:
1) Connect the positives probe of a voltmeter to the glass capacitor
(connected to the varicap) and the negative probe to ground.
2) Check that at both limits of the operating frequency band, the
voltage reading lies between 3.5 and 10.3V.
The highter frequency should correspond to the highter voltage and
vice versa.
3) If the voltages in step 2. cannot be verified ie. the PLL is not
locked, the soldered joint, connecting the SL strip-line to ground,
should be moved (the other end of the strip-line is connected to
the cathode of the varicap via caapacitor CX).
4) Should the chosen operating frequency be less than 500 MHz, the
strip-line will have been replaced by a piece of 50 Ohm teflon cable
(RG316). In this case the varicap voltage may be adjusted by varying
the length of the cable accordingly. The central conductor is
shorted to the screen at one end of this cable.
5) If the calibration procedure is being carried out after a change
of frequency, capacitor CX, situated on the VCO card, will also have
to be changed according to table D.
5.8 STEREO CODER ADJUSTMENT
After replacement of the Stereo Coder, the following procedure
should be followed SETUP 3 (Fig.6):
1) Select 0 dBm with the INPUT LEVEL selector (with stereo coder and
pilot tone inserted).
2) Connect a low distortion sine wave audio generator to the inputs
L, R.
3) Connect the RF output of PTRL-NV/S3 to a suitable load (50 Ohm-20W).
4) Connect a -30 dB coupler to the RF input of F.A.M. (or other
Modulation Analyzer type).