Transient power analysis showing a good radio
A radio with a bad frequency kick will show an erratic trace, ris-
ing in a jagged line. To ensure that this is caused by poor fre-
quency response rather than by a poor power profile, press
[Return] to get to the Transmitter test screen, followed by [Mod
Meter], [IF Filter], [300 kHz], [Return], [Return] to select the 300
kHz IF filter. Then press [Tx Power], [Trans Analys] and repeat the
test. If the trace is significantly improved, this indicates that the
frequency kick of the radio is poor.
Transient power analysis showing a bad radio with the 30 kHz
IF filter
Transient power analysis showing the same bad radio with the
300 kHz IF filter
The explanation of this is that the 30 kHz IF filter filters out all of
the signal that is transmitted out of band by the radio, whereas
the 300 kHz IF filter passes more of the signal. Hence, if the
radio is not transmitting the whole signal in the required band,
then the part of the signal which is out of band will not be dis-
played on the trace when the filter selected is 30 kHz, but will
show with the 300 kHz filter, unless the radio is exceptionally
poor. The above example shows a poor radio with a frequency
that starts in band, moves out of band, then back in again. The
slight dip in the trace with the 300 kHz filter shows that the radio
is even at the limits of the 300 kHz filter bandwidth.
Remote control
The 2945B has remote control facilities available both from the
built - in RS232 serial interface, as well as the optional GPIB
(IEE488.2) interface. It also features a built in MI-BASIC interpreter,
for user defined programs which can be downloaded from a PC.
Detailed explanation of the remote operation of the test set is
beyond the scope of this document, but all the tests that form
automatic testing and all the parameters that have been
described in this application note are available to be run remote-
ly.
Summary
The 2945B Communications Service Monitor is a versatile tool for
both routine testing and fault finding of EDACS radios.
The automatic tests, whether run directly or remotely can be used
to thoroughly test a radio and the manual testing mode is ideal for
detailed examination of particular areas of a radio's operation.
References
Operating Manual Supplement for Communications Service
Monitor 2945B and for EDACS Radios. [Part Number 46882-
301L]
Programming Manual for Communications Service Monitor
2945B [Part Number 46882-318B]
Enhanced Digital Access Communications System (EDACS) Digital
Air Interface Specification" [December 28 1995, Doc #TSB69.3]
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General