
The depth of modulation test measures the percentage (50
to 93 percent
measurement range) of amplitude modulation (AM) on the visual carrier. The
analyzer measures the horizontal synchronization-pulse level and vertical
interval test signal (VITS) white level from which it calculates the percentage
Scrambled Channels
The visual carrier AM modulation depth test may not be valid for scrambled channels, depending on
the method used to scramble the channel’s signal. So, when testing a scrambled channel, You may
want to momentarily turn off scrambling for the channel while the channel is being tested for AM
modulation depth. You can use control line A of the analyzer auxiliary interface to determine when the
analyzer is testing a scrambled channel. When testing a scrambled channel, the control A line
of the analyzer auxiliary interface is set high in transistor-to-transistor logic
To perform the depth of modulation measurement, the analyzer does the
following:
1. Changes the center frequency and reference level of the analyzer.
2. Changes the amplitude scale and span of the analyzer.
3. Measures the minimum level and the maximum level and calculates the
percentage of AM modulation depth.
Changes the center
The visual carrier is centered on the analyzer screen and a 1 MHz resolution
frequency and
bandwidth is used to capture the entire modulation signal. For better
reference level of the
accuracy, the reference level of the analyzer is changed to the level of the
analyzer
visual carrier.
8 - 2 8
Summary of Contents for 8591C
Page 2: ...I User s Guide HP 8591C Cable TV Analyzer Cable TV Measurements ...
Page 22: ...I Glossary Index Contents 7 ...
Page 27: ...Contents ...
Page 28: ...I 1 Getting Started ...
Page 33: ......
Page 43: ...I Getting Started ...
Page 44: ...I 2 Channel Measurements ...
Page 107: ...I Channel Measurements Making Channel Measurements ...
Page 108: ...3 System Measurements ...
Page 147: ...System Measurements Deleting Individual Files from a RAM Card ...
Page 148: ...I 4 If You Have a Problem ...
Page 165: ...I If You Have a Problem How to Contact Hewlett Packard ...
Page 166: ...I 5 Channel Measurements Menu Map and Softkey Descriptions ...
Page 193: ...I Channel Measurements Menu Map and Softkey Descriptions ...
Page 194: ...6 System Measurements Menu Map and Softkey Descriptions ...
Page 232: ...I 7 TV Receiver Setup and AUX CTRL Menu Maps and Softkey Descriptions ...
Page 233: ......
Page 253: ...I TV Receiver Setup and AUX CTRL Menu Maps and Softkey Descriptions Softkey Descriptions ...
Page 254: ...I 8 Test Descriptions ...
Page 301: ...Test Descriptions View Co Channel Test Description ...
Page 302: ...9 Specifications and Test Aids ...
Page 325: ...Specifications and Test Aids Channel Survey Map ...
Page 326: ...Specifications and Test Aids Channel Survey Map I Channel Line Number Number Odd ...
Page 327: ...Specifications and Test Aids Channel Survey Map Even 1 I I I I ...
Page 328: ...Specifications and Test Aids Channel Survey Map ...
Page 329: ...I Specifications and Test Aids Channel Survey Map 9 2 8 ...
Page 330: ...Specifications and Test Aids Channel Survey Map ...
Page 331: ...Specifications and Test Aids Channel Survey Map ...
Page 332: ...I Specifications and Test Aids Channel Survey Map ...
Page 333: ...Specifications and Test Aids ...
Page 334: ...Glossary ...
Page 353: ...Index ...