Programming Information
27
Note:
In both cases described above, the user should be no-
tified that the selected Eb/No is not directly supported. In
the case that the %LBW value is outside the given range on
the low side, the user should be notified that the demodula-
tor can not support the signal to noise ratio selected. In the
case that the %LBW value is on the high side of the range, the
user should be alerted that the loop bandwidth has been ad-
justed for appropriate demodulator operation.
3.3.6
Evaluation of the Demodulator Tracking Range
The tracking range of the demodulator is another factor to consider in the setup.
This tracking range takes into account variations for Doppler shift and drift of
the carrier. The tracking range will be at least three times the loop bandwidth
(LBW).
1.
Tracking Range
≥
LBW x 3
3.3.7
Calculation of the Demodulator NCO Frequency
To calculate the demodulator NCO frequency, the demodulator carrier frequen-
cy must be multiplied by a constant K. The following equation applies.
1.
f
NCO
= Demod fc x K = Demod fc x 214.74837
3.3.8
Calculation of the Data Filter Cutoff Frequency
To calculate the data filter cutoff frequency, the demodulator data rate must be
multiplied by a constant based on the demodulator PCM format selected in
Sec-
tion 3.3.1
. The following equation applies.
1.
f
D
= Demod DR x PCM Factor2
(Range 4430-V: 27Hz to 390kHz)
(Range 4430-VN: 0.75Hz to 9kHz)
Tracking Range
=
f
NCO
=
If variable Demod PCM = BI
Φ,
then PCM Factor2 = 3
If variable Demod PCM = NRZ, then PCM Factor2 = 1.5
f
D
=
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