R.V.R. Elettronica PTX30 UHT/S3, User Manual

Page: 39 / 122

PTX30 UHT /S3
33 / 36 User Manual Rev. 5.0 - 10/12/2001
10. Adjustment Procedure
10.1 Stereo coder adjustment
After changing a stereo coder board it’s necessary to make the following checks
and adjustments (see figure 10.1):
figure 10.1
•
Select 0dBm with the INPUT LEVEL selector (with stereo coder and pilot tone
inserted).
• Connect a low distortion sine wave audio generator to the inputs L, R.
•
Connect the RF output of PTX30 to a suitable load (50Ohm-30W).
•
Connect the R.F. Test -30dB to the R.F. input of F.A.M. (or other modulation
Analyzer type).
•
Connect to the rear FM-MPX output of F.A.M. a stereo measurement decoder.
•
Switch on the PTX30 and wait for the PLL to lock.
• Set the output level of the signal generator to 0 dBm (2.2Vpp or 0.775Vrms)
and 400Hz.
•
Select with the switch the R (mono) reading and if needed adjust P8 on the
coder board for a 0dB level.
•
Repeat the same adjustment selecting L (mpx) and adjusting P7.
•
Check with F.A.M. set in FM PK+ mode and with the 30Hz-200KHz filter inserted
that the deviation is 75KHz; if necessary adjust R45 on the main card to obtain
this value.