Nautel Exporter Plus, Техническое руководство по эксплуатации, Страница: 20 / 186

Exporter Plus Technical Instruction Manual Description
Page 1-8 Issue 1.0 2020-05-05
Diversity delay
A feature of any IBOC system is the receiver’s ability to transition between analog and digital
playout when digital signal reception is poor. Ideally this transition would be unnoticable for
the listener, so it is important that any delay caused by digital signal processing (approximately
eight seconds) is matched on the analog signal. Furthermore, the audio levels should be the
same. The Exporter Plus allows the user to adjust both of these parameters.
The diversity delay setpoint can be adjusted via the user interface (UI) (see Setting delay period
- see page 8-38 ), or using remote inputs. Toggling the remote diversity delay increase input
causes the diversity delay to increase by an amount established in the UI (see Setting delay
increment - see page 8-39 ).
In some cases it is desirable to remove analog delay altogether, forcing the receiver to use only
the analog reception. The need for this is prevalent during live programming, such as sporting
events, where stadium listeners need the audio to closely align with the live action.
The Exporter Plus has provision for diversity delay ramping, which allows changing between
the desired setpoint delay and no delay. The ramping function can change the delay over a pre-
defined ramp rate (set though the UI), by continuously adding (ramp up) or deleting (ramp
down) audio samples. If the ramp rate is very short, there may be noticeable effects on the
audio pitch. The amount of time taken to ramp diversity delay up or down is configured by
setting the ramp rate. The ramp rate (see Setting ramp rate - see page 8-38 ) is set as a multiple of
the diversity delay setpoint. For example, assuming a diversity delay setpoint of eight seconds
(8 s), setting the ramp rate to:
– 1 results in a ramp interval equal to the diversity delay (8 s).
– 2 result in a ramp interval twice the diversity delay (16 s).
– 100 (recommended value) results in a ramp interval of 800 s.