30 kHz Resolution Bandwidth Problems

Shape factor too high: Shape factor is the ratio of the 60 dB bandwidth to the 3 dB bandwidth. Shape factor should be less than 15:l. If one of the LC poles malfunctions, the shape factor may be the only indication of the failure. Isolate the non-functioning pole with the IF signature. Region E of Figure 8-8 illustrates the four LC- pole adjustments. Take several signatures to examine the LC-pole adjustments. If one of the four sections of Region E is consistently longer than the others, the corresponding LC pole is faulty.

IF gain compression: FET transistors Q301, Q303, Q700, and Q701 can deteriorate with age. Measuring less than 0 volts on the FET source indicates a bad FET.

Bandwidth too wide: Check for contamination on the printed-circuit board. Clean the board as required.

3 kHz and 10 kHz Resolution Bandwidth Problems

Asymmetric Filter Response: Check the crystal symmetry control with the following steps.

1.Press (PRESET).

2.Set the spectrum analyzer controls as follows:

RES BW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3kHz SPAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 kHz FREQUENCY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100kHz

3.On the spectrum analyzer, connect the 300 MHz CAL OUTPUT to the INPUT 500.

4.A trace similar to Figure 8-15 indicates a failed crystal-symmetry circuit.

Narrow 10 kHz resolution bandwidth: Check for printed-circuit board contamination. Clean the board as required.

IF Gain Compression in 10 kHz resolution bandwidth: FET transistors Q202, Q203, Q501, and Q503 can deteriorate with age. Measuring less than 0 volts on the FET source indicates a bad FET.

8-32 IF Section