Technical data

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

TEST_08. TX FM Hum and Noise

This test measures the ratio of residual frequency modulation to the reference

taken at 60% of rated system deviation. Audio connections from the radio to the

test set are required for this test.

The 400 Hz High-Pass Filter is used if Option 010 is installed in the test set.

FM hum and noise is measured in dB, from the formula:

−20×Log(Reference Deviation÷Present Deviation)

If your radio has Continuous Tone-Controlled Squelch System (CTCSS) or

Continuous Digital-Controlled Squelch System (CDCSS) available but is not

controllable, an alternate filter may be selected, if available, to reduce the effect of

the tone or code on the result. A 400 Hz HPF, C MESSAGE, or CCITT filter may

be selected.

Pass/Fail Limits Used

Pass/Fail Limit 29, TX FM Hum and Noise

Test Parameters Used

Parameter 2, RT Full Rated System Deviation

Parameter 27, TX De-emphasis