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