Arcam digital radio tuner DT81 - Manual (Page 9)

DT81
9
Troubleshooting
1. Display shows ‘Service not found’ when attempting to
select a service
This can happen when the tuner has an ensemble stored that is
no longer available. For example when the tuner is fi rst shipped
it has the BBC ensemble stored, and if it is used in another
country then that ensemble will not be available. In this situation
one should perform a search.
Note that re-confi guration of services within an ensemble is
handled without having to perform a search, so if services
are added or removed from the ensemble it is not necessary
to perform a search. Therefore ‘Service not found’ may also
appear when an attempt is made to select a service that has
been removed from the ensemble. Normally redundant services
are automatically removed from the list but occasionally they
are not. If this happens, simply select another active service
to remove redundant services fom the list of available services
and from any stored presets.
The other situation when the tuner may fail to select a service
is when the signal strength is insuffi cient. When a service is not
selected it is possible to view the signal strength in Engineering
Mode (provided an attempt has been made to select a service
from the required ensemble) . Generally the meter needs to be
past the ‘E’ in ‘Strength’ for reliable reception.
We strongly recommend that an external aerial is used for the
best possible performance. If the signal strength is marginal
then an indoor aerial will only work some of the time, as the
signal quality is affected by weather and the time of day.
Note: There will be situations where some ensembles are
strong and others are weak. With a good aerial you may be
able to weakly pick up some ensembles from outside their
normal coverage range.
2. Display shows ‘No Signal’
This message is displayed if a signal at the required frequency
is missing. Note that it may take some time (about one minute)
to show the message. If you have removed the aerial and this
message appears, reconnect the aerial and reselect a service
to restore operation.
3. Display shows ‘No services stored’ at the end of the
search
This will happen when the signal strength is insuffi cient due to
either a poor aerial or lack of an available DAB signal.
4. Audio is lost and display shows ‘signal weak – muted’
This happens when the signal becomes weak. A better aerial
is required.
5. Audio is lost and display shows ‘Service ended’ or
‘Arcam DAB Tuner’
This occurs if the selected service is no longer broadcast – in
practice this will rarely happen. Select another active service.
6. Display shows ‘No service stored’ when a preset
button is pressed
This message is shown if a service has not been assigned to
a preset button or if that service has been removed from the
ensemble, even temporarily. If ensemble components are only
partially detected (due to weak signal strength) then the tuner
sometimes decides that a service has been removed and the
preset is deleted.
Notes on data rate and sound quality
The tuner supports MPEG audio data rates up to 256 kb/s
which is the maximum rate as defi ned by the ETSI specifi cation
for DAB radio.
Data rates transmitted are generally lower than this because
broadcasters prefer to include a high number of services within
the available bandwidth. Higher compression factors are used
to lower data rates, reducing audio quality.
Most stereo services operate at 192kb/s at present, and this
has been found to give very high quality audio (though 256kb/s
is even better).
Some speech-based services use mono in order to reduce
the data rate and some apply higher compression as well. It
is also common to fi nd that different services have different
audio quality even though they operate at the same data rate.
This is due to differences in the audio processing techniques
used in the transmission chain. Generally speaking, audio
is transmitted without applying dynamic range compression
(DRC) – unlike FM broadcasts. DAB uses a system whereby
the coeffi cients for DRC are transmitted separately, so that
the tuner can apply the compression itself. This is benefi cial
because the listener can decide whether or not to apply DRC:
most hi-fi enthusiasts do not. However some DAB broadcasts
have some form of DRC applied directly to the audio and this
generally impairs audio quality.