Model 8640B TM 9-4935-601-14-7&P
SETTING FREQUENCY AND AMPLITUDE
NOTE
If the OVERFLOW annunciator lamp is lit, the generator will not enter phase lock. If the TIME
BASE VERN is not in the CAL position, the counter will not be calibrated.
f. Whenever phase lock is lost, the FREQUENCY display (6) will flash. To re-establish phase lock, set COUNTER
MODE LOCK (5) to OFF; re-tune (if necessary) with FREQUENCY TUNE (12) and FINE TUNE (11), and set
COUNTER MODE LOCK to ON.
NOTE
To get an accurate indication of frequency when not phase locked, set TIME BASE VERNIER (7)
to CAL.
g. To use an external frequency doubler, connect to RF OUTPUT (9) and set RANGE (13) to 512-1024
MHz/DOUBLER. The FREQUENCY display (5) will indicate the frequency out of doubler (i.e., the FREQUENCY
display indicates twice the frequency at RF Output).
Amplitude
a. Use the OUTPUT LEVEL switch and vernier (11) to set the desired signal level (there are two scales, rms volts
and dBm). For optimum operation, use the vernier in the top 10 dB of its range. To enable the RF signal, set the
RF ON/OFF switch (8) to ON.
NOTE
The RF ON/OFF switch may be wired to turn off only the amplitude modulator. This allows the
RF Oscillator to remain warmed up, the Auxiliary RF Output to remain on, and the counter and
phase lock to remain operating. If it is desirable to switch both the modulator and the oscillator
off, the RF ON/OFF function may be easily modified (see Service Sheet 5 in Section VIII).
Figure 3-5. Setting the Frequency and Amplitude Controls (2 of 3)
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