Tektronix 1720 User Manual

Operating Instructions
1720/1721
2–25
signal at a time and adjusting its gain to correspond to the appropriate axis
(horizontal to the X axis and vertical to the Y axis).
Once both signal gains are normalized they can be displayed in the XY Mode
and the relative stereo phase measured.
The High-Gain X and Y inputs of the 1720/1721 can be used to look at ICPM
(Incidental Carrier Phase Modulation). ICPM is a change in carrier phase with a
signal level change. It will show up as apparent differences between measure-
ments made in synchronous and envelope detection modes. On home receivers,
with envelope detectors, the picture will be uneffected if the visual transmitter
has been adjusted using envelope detection when there is appreciable ICPM.
However, ICPM can show up in the home receivers audio as intercarrier buzz.
ICPM can be looked at by applying the Video and Quadrature Outputs from a
demodulator to the 1720/1721 X and Y Inputs. The Quadrature Output drives
the High-Gain X Input and the Video Output drives the High-Gain Y Input. The
resulting display will be vertical when ICPM is minimum, and tilted when ICPM
is present.
NOTE. This is not a definitive measurement, but does provide a way of
determining if ICPM is present in the signal.
Looking at Incidental
Carrier Phase Modulation

Tektronix 1720 Specifications

General

Brand	Tektronix
Model	1720
Category	Measuring Instruments
Language	English