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Twin Modulator
d. Audio Menu
Pressing
accesses the next menu. In this menu,
it is possible to con fi gure the modulation audio
parameters, audio deviation, audio carrier
frequency relative to that of the video and audio
sub-carrier frequency (5.74 MHz) relative to that of
video
(*)
.
(*) Only in the case where the main audio carrier is at
5.5MHz.
Initially, a short press on the parameter selection
key
gives access to the A/B modulator selection
menu; then use keys
and
to select A or B.
A short press on the parameter selection key
gives access the audio deviation sub-menu
(AudDev). Modify the audio deviation value
between 0 to 13, by using keys
shown in the next table indicate the audio level
necessary at the input (for an input signal of 1 KHz)
in order to obtain a modulation deviation value of
50 KHz in Dual mode. In other words, if the input
signal is 1.7 Vpp at 1 KHz (0 dBm in the audio
analyser), we need to program the AudDev menu
of the programmer with a value of 6.
S. Dev.:
0
1
2
3
4
5
6
7
8
9
10
11
12
13
For an input audio level of 1Vpp for a 1KHz signal
(-7,5dBm in the audio analyser), the modulation
deviation will depend on the AudDev value
programmed as indicated in the following table:
S. Dev.:
0
or
. Values
1
2
3
4
5
6
7
8
9
Input level audio (dBm)
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
Modulation Deviation KHz
±11.5
±13
±14
±15
±17
±19
±22
±25
±28
±31
10
±34
11
±37.5
12
±40
13
±45
If the modulator programmer is in L Norm, these
values indicate the modulation depth: m=100*
[(Emax-Emin)/(Emax+Emin)] provided that the
input level is 1 Vpp for a 1 KHz signal.
S. Dev.:
L Norm (1Vpp)
0
20%
1
22%
2
24%
3
26%
4
29%
5
32.6%
6
36.7%
7
39.5%
8
45.8%
9
49%
10
54%
11
60%
12
68.5%
13
77%
Short pressing the parameter selection key again
accesses the selection sub-menu for audio carrier
level relative to that of the video (RelPort) which
can be changed by pressing
and
16
.
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