B3 single-channel A mixer tuning

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B3 single-channel A mixer tuning

User's Manual for B3 Tuning Channel A in Single-Polarity Mode

Receiver B3 is a dual-channel system, and if you want to tune in single channel mode normally we recommend using channel B because the bandpass is cleaner and wider than that of channel A. However, on occasion there may be a good reason to use channel A (such as channel B being out of commission) and in this case there are some special tricks required.

The Problem

When B3 is tuned in single-polarity Chan A mode, the modulator module fails to switch to channel A from "Independent" mode, and the mixer junction current as displayed on the control room B3 screen sticks at 40.0, when the demand value is 20.0 microamps (or,in general, twice the demand value). Single-polarity channel B works fine.

The Solution
Go to the receiver cabin and put the Channel Mode switch on the MODULATOR module up from the Independent to Chan A position. Then put the MODULATOR into LOCAL mode and leave it there.

At this point the Chan A junction current, as shown on the LED displays in the receiver cabin and on the control room screen, should read the demand value.

Proceed with observations.

Contact: Ming Zhu. Updated: Mon Aug 16 16:17:36 HST 2004

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