5.Log Amplifier Adjustments

Reference

5. Log Amplifier Adjustments

IF-Display Section

A4A3 Log Amplifier-FilterA4A2 Log Amplifier-Detector
Related Performance Tests

Note

Scale Fidelity Test

The A4A3 Log Amplifier-Filter and A4A2 Log Amplifier Detector are temperature compensated as a matched set at the factory. In the event of a circuit failure, a new matched set must be ordered. Contact your nearest HP Service Center.

Description First, the A4A2 Log Amplifier-Detector ZERO adjustment is checked and adjusted if necessary, then the A4A3 Log Amplifier-Filter is set for center frequency by injecting a signal and adjusting the bandpass filter center adjustment for maximum DVM indication. The bandpass filter amplitude is adjusted by monitoring the output of the filter control line shorted and not shorted to the + 15V supply. Next, log fidelity (gain and offset of the log curve) is adjusted by adjusting the -12 VTV and the PIN diode attenuator. Last, the linear gain step adjustments are performed to set the proper amount of step gain in the linear mode of operation.

S Y N T H E S I Z E R L E V E L

GENERAT 6R

D I G I T A L V O L T M E T E R

S P E C T R U M A N A L Y Z E R ‘$,,,

I

Equipment

Procedure

Figure 3-33. Log Amplifier Adjustments Setup

Digital Voltmeter (DVM) . . . . . . . . . . . . . . . . . . . . . . . . HP 3456A Frequency Synthesizer . . . . . . . . . . . . . . . . . . . . . . . . . HP 3335A

1.Position instrument upright as shown in Figure 3-33, with top cover removed.2.Set LINE switch to ON and press (INSTR PRESET].3.Key in [FREQUENCY SPAN) 0 Hz, &ENTER FREQUENCY] 7.6 MHz,CREFERENCE LEVEL_) + 10 dBm, [RESBW) 10 kHz, and press LIN pushbutton.

Adjustments 3-65