Internal Reference Oscillators; Rf Input 3 Ghz - Fluke PM6690 Service Manual

Internal Reference
Oscillators
Adjustment of the different timebase oscillators is described
under Calibration earlier in this chapter.

RF Input 3 GHz

Note: The 8 GHz prescaler can not be adjusted.
n
Setup
– Do as described under Preparations above.
– Select default settings by keying in
®
Save/Recall Recall Setup
– Select measurement function FREQUENCY C.
– Set the signal generator to 1000 ± 25 MHz with ampli-
tude 5.9 ± 0.5 mV (-31.5 ± 0.5 dBm)
rms
n
Adjustment
– Connect the signal to Input C on the timer/counter.
NOTE: Before beginning any adjustments, the RF input
must have been in operation for at least a few minutes
to let it reach normal operating temperature.
– Turn the potentiometer on the prescaler board fully
counterclockwise. See Figure 7-6.
– Check that the timer/counter stops measuring.
– Turn the potentiometer slowly clockwise until the
timer/counter starts measuring.
– Check the display of the timer/counter, it shall show
1000 ± 25 MHz.
AC/DC BOARD
Figure 7-6
Adjusting the 3 GHz RF prescaler.

7-14 Internal Reference Oscillators

®
USER OPT
®
Default
INITIAL SETTING:
FULLY CCW
3 GHz PRESCALER
MAIN INPUT
AMPLIFIERS