(fM/N), and the YTO frequencies, refer to Table 2, M and N Numbers and Resulting Frequencies.

20/30 Synthesizer Tuning

When a start frequency change occurs, the YTO is pretuned near the new desired frequency by the A19 Digital-Analog Converter and A20 Main Coil Driver. This places the YTO frequency 20 to 30 MHz below the Nth harmonic of the M/N Loop output. (The Nth harmonic is the same as the M/N Loop’s N number.) The YTO frequency and the M/N Loop harmonic are mixed in the AllA Sampler. The YTO IF (20- 30 MHz) is phase compared with the 20/30 Synthesizer output. The AllA Phase Detector’s error voltage is then used to tune the YTO through the A21 FM Coil Driver and the A20 Main Coil Driver to achieve phase-lock.

The 20/30 Synthesizer is used to pretune the YTO in 1 Hz steps (in zero frequency span) through a 10 MHz range. The following formula expresses the relationship between the frequencies found in the YTO Loop.

&o/so (N x fM/N) - f0 = fYTOIF

Where:

f2u,su = 20/30 Synthesizer frequency. (Displayed with KSR.)

N = N number, varies from 11 - 32. (KSR displays value of N.)

fM/N = M/N Loop frequency

fo = YTO frequency

fYToIF = YTO IF frequency

The 20/30 Synthesizer frequency can also be determined by using the YTO frequency set. This frequency is available by using KSR. In this case,

f2,,/s,, = (30.000000 - D7 D6 Ds D4 Ds Dz Dr)

Where:

Dr to Dr is the YTO frequency displayed with Dr being the least significant digit (1 Hz).

Marker Mode

When the MARKER @GG) mode is selected, the analyzer does the following. First, the center frequency is determined. Because the @GGiJ marker is a display marker, after the center frequency is calculated, the position of the marker on the display is determined. By knowing that the display consists of 1000 points and the programmed frequency span, the processor calculates the offset between the center frequency and the marker. The frequency span accuracy is the major cause of error in the readout accuracy of the MARKER (NORMAL] mode.

6 Analog Troubleshooting