Technical Instruction
Table Of Contents
- Nautel Limited
- MODULE EXCHANGE SERVICE
- 6.1 INTRODUCTION
- 6.2 WIRING LISTS NOT PROVIDED
- 6.3 PRINTED WIRING PATTERNS
- 6.4 WIRE COLOURS
- 5.5 WIRING LISTS PROVIDED
- 7.1 INTRODUCTION
- 7.2 COMPONENT VALUES
- 7.3 GRAPHIC SYMBOLS
- 7.4 LOGIC SYMBOLS
- 7.5 REFERENCE DESIGNATIONS
- 7.5.1 Types of Inputs/Outputs
- 7.5.2 Logic Level/Convention
- 7.7 IDENTIFICATION OF SCHEMATIC DIAGRAMS
Page 3-10 VSHD Exciter Technical Instruction Manual
Issue 2.0 Section 3 Operation
- Timeout Seconds: sets the delay, in seconds, between modulation loss
detection and the resulting action. Enter a value in the allowable range of 0 and
59.9 seconds.
- Threshold: sets the threshold for modulation loss detection. Enter a value in the
allowable range of 0 and 100%.
- Hard Limiter: select Enabled, then enter the hard limit threshold percentage (allowable
range is 0-160%, defaulted to 140%). If enabled, the modulation level will be limited
(audio signal clipped or distorted) if it exceeds the hard limit threshold.
- AGC Limiter: select Enabled, then enter AGC Limit percentage (allowable range is 0-
160%, defaulted to 120%) and Time Constant (allowable range is 0-1000 ms, defaulted
to 0 ms). If Enabled, when the modulation level exceeds the AGC Limit, the gain of the
audio input will instantly decrease in order to reduce the modulation level below the
AGC limit threshold. Recovery from this audio gain reduction is dependent on the Time
Constant delay (fast attack, slow recovery). The input signal is briefly distorted by the
audio gain reduction when the threshold is exceeded.
- Two Slope Limiter: if Enabled, when the modulation level exceeds the Threshold, the
gain of the audio input will instantly change according to the gain percentage setting
(percentage of the initial gain, that which is below the threshold). The input signal is
distorted by the audio gain change.
- Threshold: allowable range is 0-160%, defaulted to 120%.
- Gain: allowable range is 0-100%, defaulted to 56.2%.
- L/R Limiter: this look-ahead limiter can be applied to the signal immediately before the
stereo generator in the exciter. It has a fixed attack time (and corresponding delay) of
approximately 1 ms. It can be configured to reduce the signal, if the gain setting is 0 dB
or less, or can be used to perform an AGC function and boost quiet sections of the
audio if a positive gain setting is used. If Enabled, enter the following parameters:
- Max Gain: allowable range is -20 to 20 dB, defaulted to 0 dB.
- Decay Time: allowable range is 0 to 60 s, defaulted to 0 s.
- Hold Time: allowable range is 0 to 60 s, defaulted to 0 s.
- MPX Power Limiter: if Enabled, enter MPX RMS Limit. This limit allows the broadcast
signal to remain in compliance with the MPX power limits as suggested in ITU-R
BS.412-9. While the limiter will keep the transmitter in compliance, it is recommended
that adjustment to the processing be made in such a way as to minimize the reductions
performed by the limiter. Otherwise, the signal will not take advantage of the peak
modulation capability available.
MPX RMS Limit: (allowable range is -12 to 12 dBr, defaulted to 0 dBr).
NOTE
MPX RMS is displayed as a percentage (%) on the meters screen. The percentage (%)
equivalent for the dBr range shown above are 4.5% (-12 dBr) to 71.3% (12 dBr); default is
17.9% (0 dBr).
Convert to dBr as follows:
MPX RMS in dBr = 20 log 10 [MPX RMS in % * (75 kHz/100%) * (√2/19 kHz)]