10.Step Gain and 18.4 MHz Local Oscillator Adjustments

Reference

10. Step Gain and 18.4 MHz Local Oscillator Adjustments

IF-Display Section

A4A7 3 MHz Bandwidth Filter

A4A5 Step Gain

Related Performance Tests

Description

Resolution Bandwidth Selectivity Test

IF Gain Uncertainty Test

Center Frequency Readout Accuracy Test

First, the IF signal from the RF Section is measured with a power meter and adjusted for proper level. Next, the 10 dB gain steps are adjusted by connecting the CAL OUTPUT signal through two step attenuators to the RF INPUT and keying in the REFERENCE LEVEL necessary to activate each of the gain steps, while compensating for the increased gain with the step attenuators.

The 1 dB gain steps are checked in the same fashion as the 10 dB gain steps, and then the variable gain is adjusted. The 18.4 MHz oscillator frequency is adjusted to provide adequate adjustment range of front-panel FREQ ZERO control; and last, the + 1OV temperature compensation supply used by the A4A4 Bandwidth Filter and A4A8 Attenuator-Bandwidth Filter is checked and adjusted if necessary.

PMR METER

DIGITAL VOLTMETER

fi!&

1OdB S T E P 1 dB S T E P ATTENUATOR ATTENUATOR

Figure 3-46.

Step Gain and 18.4 MHz Local Oscillator Adjustments Setup

Adjustments 3-87