Adjustment Procedures
5-46 2715 Spectrum Analyzer Service Manual
Adjust Downconverter Local Oscillator. Adjust R59 and R63 as follows:
1. Reconnect the 110 MHz input signal (from the RF Mother board) to the
Video Demodboard 110M IN connector.
2. Move the input cable of the test spectrum analyzerfrom TP110M (on the
Video Demodboard) to TP45M.
3. Set the test spectrum analyzer as follows :
Center Frequency 45 MHz
Reference Level -- 30 dBm
Span/Div 1 MHz
4. Initialize the 2715 setting by pressingUTIL 1 1.
5. Select the following settings on the 2715:
CENTER FREQUENCY 100 MHz
REFERENCE LEVEL 18.8 dBmV
RESOLUTION BANDWIDTH 1 MHz
SPAN ZERO
Calibrator Signal ON
Markers OFF
6. Activate the TOGGLE VD DAC LO/HI function by pressing UTIL525.
NOTE. When performing steps 7 through10 you will be adjusting the operating
frequencyand tuning range of the Downconverter Local Oscillator. While
making the adjusts, use menu item 5 (TOGGLE VD DAC LO/HI) to toggle the
frequencybetween the two values (41 and 47 MHz as indicated by the “41 SET”
or “47 SET”at the end of the menu line).
The object of the procedureis to set R63 and R59 so that the frequencies
produced in both states areeach within 100 kHz of the nominal value.
7. Adjust the video demod BIAS (R63) so that the signal peaks, in both states
(41SETand47SET),arevisibleonthetestspectrumanalyzer’s screen. If
necessary adjust RANGE (R59) towardthe counterclockwise end of its
rotation.
8. Adjust RANGE (R59) so that the two signal peak locations are6.0 MHz
apart.
9. Adjust BIAS (R63) so that the lower frequencysignal is located at 41 MHz
±100 kHz.
10. Alternately adjust R59 and R63 to eliminate interactionuntil the lower
frequency peak is at41 MHz ±100 kHz and the upper peak is at 47.0 MHz
±100 kHz.