>@9
Multitone Audio Test System
User Manual
V 3.32
37 / 71
Obviously, the levels of the five signal bins, together with their frequencies, make the
uniqueness of the
>@9
trigger signal.
The application of the User trigger allows to individually define the ’headroom’ between the
0dB line and the bottom bars (
T
). However, this is a very delicate operation, and therefore
not recommended for new users of
>@9
. Anyway, in case that this feature truly has to be
used, please refer to the explanations of the commands
INPut:TRIGger:CONFiguration ...
and
INPut:TRIGger:USRConfiguration ...
as well as to the helpfile of the RT-EVAL software
package.
Remains the question about the reference level of the analyzer, since especially for long-
distance transmission lines, this instrument cannot use the same reference voltage potential
as the generator.
The solution is to assume the currently set input range of the analyzing
>@9
unit as
reference level. This level equals the max. detectable amplitude of all incoming signals (all
higher levels would be clipped), and is represented by the 0dB line on top of
Fig. 24
.
Consequently, all received signals will be analyzed against 0dB. Applied on the trigger
detection criteria, this means that the level pattern of an incoming multitone trigger must be
within a certain range, defined by the trigger configuration of the analyzer.
Application Hints / Troubleshooting
To execute measurements in the broadcast mode is probably one of the more demanding
procedures when working with
>@9
, mainly because of the remote location between the
generator and analyzer, i.e. the sender and receiver of the multitone burst.
Nevertheless, by considering both the instructions listed in chapter
Setup
(p.
35
) and
following hints, it shouldn’t become a major problem to establish a properly working set up.
•
The most effective approach to successfully execute a first test run, is to place the
sender & receiver not too far apart (e.g. in the same room), however, with both units
already being controlled by individual PCs. Such a setup may probably not include a long
transmission line, but is ideally suited to adjust the required settings of the majority of the
involved systems to allow a proper measurement.
•
For the first signal transmissions / measurements, reduce the number of involved stages
to a minimum, to simplify the search for possible errors. As soon as the first successful
tests are completed, the number of systems in the signal path may be increased
stepwise, and the respective settings may be optimized to the actual demands.
•
A very helpful tool to find out possible problems is to use a monitor speaker to make the
transmitted multitone burst audible at the different stages of the line. Consequently, by
listening to the sound of the burst, the operator may simply localize critical components
and optimize their transmission behaviour.
The most frequent obstacle in the broadcast mode is the ’refusal’ of the analyzer to trigger to
the incoming multitone burst. This effect is usually caused by improper adjustments of the
involved
>@9
generator / analyzer, or by sound enhancing instruments (e.g. equalizer,
compressor, limiter, compander etc.) on the transmission line, which modify the trigger signal
in a way, that it can’t be recognized anymore.
Consequently, the efforts to overcome missing triggerings have to focus on the proper
adjustment of the sending and the receiving
>@9
, as well as on the mutual optimization
between the trigger signal and the sound enhancing systems.
Possible Cause
Effect
Suggested Solution
