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The equation for start frequency is:
fSF
(B
W
X
fM/N
-
fm/m))
+ fIF
Where:
fsF
= Start Frequency
B
=
band number. KSR displays the value of B which varies from 0 to 4. When the
displayed value is 0 (low band), use 1 as a multiplier.
N
=
N number for M/N Loop. KSR displays the value of N which varies from 11 to 32.
fM,N
= M/N loop frequency in MHz. KSR displays the value which ranges from 177 to 197
MHz.
f20/30
= Synthesizer frequency in MHz. KSR displays the value which ranges from 20 to 30
MHz.
fIF
= Signal IF frequency. The value is -3621.4 MHz for band 0, -321.4 MHz for band 1,
and
+321.4
MHz
for
bands
2,
3,
and
4.
Note
For a detailed explanation of the Frequency Diagnostic Function (KSR), see
Diagnostic Functions in the Spectrum Analyzer Overall Troubleshooting
Section of this manual.
As an example, these values are used following an INSTR PRESET
([a]
pressed) to
determine the start frequency.
B=l
N=13
fM/N
180.769231 MHz
f2elsu= 28.600000
fIF=
-321.4 MHz
Substitute these values into the equation.
fSF
= (1 x(13 x 180 x 769231 MHz)
-
28.600000 MHz)
-
321.4 MHz = 2000.0 MHz
M/N Loop Tuning
The frequency output of the M/N Loop is dependent on the ratio of M and N numbers. These
numbers are input in the form of digital tuning information to the M/N Loop Phase Detector.
The following equation shows the relationship between the output frequency and the M and N
numbers.
fM/N
= (200
-
lO(M/N))
MHz
Where:
fM/N
=
M/N output frequency
M = M number which varies from 8
-
27. KSR displays the value of M.
N = N number which varies from 11
-
32. KSR displays the value of N.
The M and N numbers are selected such that the M/N Loop output pretunes the YTO
frequency in 10 MHz steps. For a listing of the M and N numbers, M/N output frequencies
Analog Troubleshooting 5