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TV measurement
39
Audio Carrier Distance and Level
TV transmitters can use a second audio carrier to transmit information
using FM modulation (analogue) or in Nicam format (digital). Different
frequencies are allocated to the audio carriers depending on the standard
being used (see table). Audio carrier 1 is always the default setting after
you have entered the channel or frequency.
Standard Audio carrier
1
Audio carrier
2
Nicam
B/G 5.5 MHz 5.74 MHz 5.85 MHz
D/K 6.5 MHz 6.26 MHz 5.85 MHz
I 6.0 MHz ------ 6.552 MHz
M/N 4.5 MHz 4.72 MHz ------
L AM 6.5 MHz ------ 5.85 MHz
M1 (Japan) 4.5 MHz ------ ------
When the audio carrier is measured, first the signal distance between the
audio and the visual carriers is measured in dB. Then the absolute audio
carrier level is measured in dBìV. During the measurement the
loudspeakers are muted. After measurement the modulation of the audio
carrier last measured can be heard.
Overview of commands in Measuring Audio Carrier Frequency
[2ndF] [SC] Switch over to the Audio Carrier menu
[1]...[2] Switch between audio carrier 1 and audio carrier 2
(see table).
With the Measuring Audio Carrier Level button
pressed,
[3] Switch over to Nicam reception
Example
Measure the audio carrier distance and level of audio carrier 1:
Press [2ndF] [SC],
Now press [1] and keep the button pressed.
The LC display shows the following values for approx. 1 second:
Audio carrier distance frequency: 5.5 MHz
Audio carrier video carrier distance: -13 dB
After approx. 1 second the audio carrier level is displayed.
LC display:
Audio carrier distance frequency: 5.5 MHz
Audio carrier level: 58.5 dBìV
Release button [1].
Measure audio carrier distance and level of audio carrier 2:
0
ë
SC: 5.50MHz TV
LEV: -13.0dB
SC: 5.50MHz TV
LEV: 58.5dBuV