User`s guide

Chapter 2 39

Test Descriptions

TEST_14 - RXA Expandor

Description

This test measures the expandor’s zero reference level and operating

range. For every 1 dB change in input level, there should be a nominal

output level change of 2 dB.

NOTE

Audio connections from the radio to the test system are required for this

test.

Expandor response is expressed in dBV for the zero reference level, and

in dB for the tracking error over the indicated operating range.

• The expandor response is measured at a 1 kHz rate and an RF input

level of

−50 dBm.

• A 2.9 kHz (1.5 kHz for narrow analog operation) deviation is applied

and the “zero crossing” of the receiver is measured. This value is

retained as the reference level.

• The input is varied from a high level of +10.6 dB above the measured

reference level to a level of

−21 dB below the measured reference

level in steps set by parameter 24. RXA Expandor Step Level (dB).

The rms deviation is measured and the expandor response relative

to the reference is calculated.

• Deviation is varied over the range and the expandor response

relative to the “zero crossing” point is calculated.

• The sweep will go from a high level (+10.6 dB) to a low level (

−21 dB)

if the sign of the step level set by parameter 24. RXA Expandor Step

Level (dB) is negative. The sweep will go from a low to high level if

the sign of parameter 23 is positive.

Background

An expandor is used to provide the complement of the compressor in the

cell site transmitter. Together, the compressor and expandor provide

improved signal-to-noise-ratio in the demodulated audio.

Pass/Fail Limits Used

• 4. RXA Expandor Tracking Error <0dB (dB)

• 5. RXA Expandor Tracking Error >0dB (dB)

• 6. RXA Expandor Zero Reference Level (dBV)

• 8. RXA NAMPS Expandor Zero Reference Level (dBV)