Tektronix 2715 Video Demodulator and Gating Verification

Performance Verification
2715 Spectrum Analyzer Service Manual 4-33
This procedure assures the properoperation of the Video Demodulator and the
gated measurement circuitry.Since this is not a Performance Requirement,
typical values are used throughout the procedure.
HTest equipmentrequired:
PAL/NTSC Signal Generator(TSG 95)
CATVModulator (TVM450)
1. Connect the TSG 95 VideoOutput to the TVM450 Video Input.
2. Connect the TVM450 -- 20 dB RF TEST Output to the 2715 RF INPUT.
3. Set the TSG 95 to produce 5-Step Grayscaleand set it to the desired video
format (NTSC or PAL).
4. Set the TVM450 output to Channel 4 and the RF level control full counter-
clockwise.
NOTE. Be sure the Offsetsw itchon the rear panel of the TVM450 is set to OFF.
5. Check that the VIDEO MODULATIONand VIDEO/AUDIO RATIO
controls on the TVM450 are both set to midrange(detent) and that the
AUDIO DEVIATIONcontrol is set full counterclockwise.
6. Select the following settings on the 2715:
FREQUENCY 67.25 MHz
RESOLUTION BW 300 kHz
VID FLTR OFF
DISPLAY STORAGE D (only)
REFERENCE LEVEL +30 dBmV
7. Press PEAK FIND,CTR-MEAS/TRKG and manually reset the center
frequency to the actualcounted visual carrier frequency.
8. Press ZERO (SPAN)an d set Sweep Speed to 100 s/div.
9. Press UTIL526to tune the video demodulatorto the visual carrier.
10. Press 7to activate the AFC. If it indicates ON, press 7twice more to toggle
it OFF then back ON.
11. Press 8to select GATING. If it already indicates GATING, press 8 twice
more to toggle it through NOR back to GATING.
12. Press any MENU key to exit the menus, and turn offthe readouts. Check
that the display is similar to that illustratedin Figure 4--7.
Video Demodulator and
Gating Verification