DT81

7

Selection mode

Press the 

MENU

 button four times to access the Selection 

Mode menu. This can be used to change the way services are 
selected when scrolling with the rotary controller or when using 
the 

<

 and 

>

 buttons on the remote control.

To change between ‘AUTO’ and ‘MANUAL’, turn the rotary 
controller and press 

SELECT

 to confi rm the setting: the tuner 

reverts to displaying the service name.

With the selection mode set to manual, the displayed service 
name is selected by pressing the 

SELECT

 button on the tuner 

or the 

BAND

 button on the remote control. When the selection 

mode is set to auto, the displayed service is automatically 
selected after 2.5 seconds.

TUNER BYPASS switch

The front panel Tuner Bypass switch is used to switch between 
this tuner’s 

AUDIO OUTPUT

 and the audio output of an FM tuner 

attached to the 

FM TUNER INPUT

 sockets. The digital output 

continues to output the audio signal from the currently selected 
digital service on the DT81.

A note on Programme types

The Programme Type (PT) label is the short description 
displayed below the service name.

Two different PT labels are transmitted: 

Static PT

 and 

Dynamic PT

. The static PT is the service ‘genre’ and does 

not change. Radio 4’s static PT for example is ‘Current affairs’. 
The dynamic PT refl ects the current programme’s content (for 
example, for Radio 4 typical dynamic PTs include ‘Drama’, 
‘News’, etc.).

When a service is selected, the dynamic PT is displayed; at 
other times the static PT is shown. This means that Radio 4 
will say ‘Current affairs’ while scrolling through services, then 
may change to ‘Drama’ when that service is selected. The tuner 
works this way because it cannot update dynamic PTs for a 
multiplex to which it is not currently tuned.

Note also that, for secondary services, the tuner displays the 
parent’s static PT, since a dynamic PT would not be relevant. 

A note on Secondary services

Primary services can have one or more secondary services 
attached to them. These tend to be temporary; sporting 
events like football matches for example may be broadcast 
as secondary services. Services that have secondary services 
attached to them are indicated by a 

>>

 symbol. Turning the 

rotary selector clockwise will then reveal these services. The 
secondary services themselves are indicated by a 

<<

 symbol.

You need to select a main service in order to see if there 
are secondary services attached. The BBC is currently not 
distinguishing between primary and secondary services, to 
work with tuners that do not support secondary services. The 
effect of this is to make those services appear twice in the list, 
once as primary and once as secondary.

Note that only primary services can be attached to a preset.

Dynamic label

This is a 128 character block of scrolling text used by most 
broadcasters to display programme information (such as song 
titles, useful phone numbers and website addresses).

Signal quality meter

The signal quality meter is a simple bargraph which gives a 
quick visual guide to reception quality. Technically, it is an 
inverse measure of the Viterbi error rate, with zero errors at 
full scale (all segments are lit) and 300 errors/second (with 
all segments off). When reception is marginal, the number of 
segments displayed becomes a very sensitive function of the 
received signal strength and can be used to optimize the aerial 
position.

Engineering mode

The DT81 digital radio tuner has two modes – in addition 
to 

User Mode

 (in which the unit powers up) it also offers 

an 

Engineering Mode

 that allows you to view technical 

information about the currently selected service.

To access Engineering Mode, press 

SELECT

 and preset 

8

simultaneously. ‘ENGINEERING MODE’ is briefl y displayed. From 
Engineering Mode you can return to User Mode by pressing 

SELECT

 and preset 

8

 simultaneously again.

Once in Engineering Mode, each of the eight preset buttons 
shows different technical information:

Preset 1: Ensemble frequency

. This is the carrier frequency 

of the currently selected ensemble.

Preset 2: Service data rate

. This is the data rate of the 

current service in kilobits per second: the higher the number, 
the better the sound quality. 

Preset 3: Service start and end CU numbers

. The start 

and end CU (Capacity Unit) numbers indicate the service’s 
position within the ensemble.

Preset 4: Viterbi error/CRC failure count

. The Viterbi rate 

indicates the amount of error correction that is going on. Audio 
decoding normally works transparently with Viterbi rates up 
to about 200; above this, audible degradation of the signal 
may be noticeable. The CRC (Cyclic Redundancy Check) failure 
count indicates the amount of uncorrected errors. Any fi gure 
above zero may mean audio disruption.

Preset 5: Signal strength (AGC)

. A measure of raw RF 

strength at the receiver front end.

Preset 6: Transmitter ID information

. This shows the IDs 

(identities) of all the transmitters detected for the current 
ensemble. DAB radio uses multiple transmitters for the same 
signal and can add together for better results. If you turn the 
rotor you can see how many transmitters are being picked up 
and their respective fi eld strengths on a scale of 1 to 7.

Preset 7: Audio mode

. This shows that the selected 

programme is being transmitted in Stereo, Joint Stereo or 
Mono mode. (Joint stereo is an MPEG audio mode where the 
data for one channel is sent along with data representing the 
difference between the two channels. It allows a lower data rate 
to be used, but is not as good quality as true stereo.)

Preset 8: Transmission mode

. This indicates which of four 

possible methods of encoding/decoding transmissions is used 
in the current service. This information may be useful to 
engineers in diagnosing certain unusual problems.