Technical data

94 S:\hp11807a\OPT001\USRGUIDE\BOOK\chapters\descrptn.fb

Chapter 4, Test, Parameter, and Pass/Fail Limit Descriptions

TEST_04. TX Modulation Limiting

This test measures the ability of the transmitter’s circuits to prevent the transmitter

from producing deviations in excess of a rated system deviation. During testing,

the audio input is over driven at a constant level while the modulation rate is

stepped from 300 Hz to 3 kHz (step size is determined by

Parameter 30, TX

Modulation Limiting Sweep Step Freq

). The instantaneous peak+ and peak−

frequency deviation is measured and reported, along with the steady-state

frequency deviation measured at each step.

Modulation limiting is measured in kHz. Audio connections from the radio to the

test set are required for this test.

If your radio has Continuous Digital-Controlled Squelch System (CDCSS), the

added signal can cause this test to fail. In this case, disable the CDCSS circuitry.

Pass/Fail Limits Used

Pass/Fail Limit 32, TX Modulation Limiting

Test Parameters Used

Parameter 2, RT Full Rated System Deviation

Parameter 30, TX Modulation Limiting Sweep Step Freq

Testing Conditions Defined by the Software

• Audio input level is increased 20 dB above the level required to produce 60% of rated

system deviation.

• The instantaneous peak+ and peak− frequency deviation is measured at a 1 kHz rate.

• The steady-state for peak+ and peak− deviation is measured with:

• The start frequency set to 300 Hz.

• The stop frequency set to 3 kHz.

• If test 29 is set to “0”, then the steady-state deviation is only measured at a 1 kHz rate.