Garmin APOLLO GX SERIES Service Manual

Contents

Garmin AT Rev --© 2004 Garmin AT GX Service Manual 7-45Reference Sensitivity and Squelch Threshold SensitivityStep General Instruction Specific Instructions Expected Results1 Set all testequipment asspecified in TestEquipment Setup onpage 7-17.2 Sig. Gen. Mod Lvl.To 30%.Amplitude to 1000μV.On the HP8920:1. Set AFGen1 to AM 30%.2. Set AMPLITUDE to 1000μV.3. Set Ext. Load R 4 ohms.3 Move test cable. On the test box, connect theHP8920 audio in cable to SPKROUT.4 Adjust volumecontrol on Commradio for 12 W.On the Comm radio, adjust thevolume control until the AC Levelreads 12 watts.≥12 watts output into 4 ohmload (mounted in test fixture) ata volume level from 0 to 12watts.5 Open squelch. On the Comm radio, pull theSquelch knob out (disablesquelch).6 Get 6 dB SINADreading and recordreference sensitivity.On the HP8920:1. Set the value field in theSINAD meter reading toaverage (AVG) at 10.2. Set AMPLITUDE using the ↓down arrow until the SINADmeter reads 6 dB SINAD.3. Record AMPLITUDE asreference sensitivity.4. The volume on the HP8920can be adjusted to monitorthe Comm radio audio.<2 μV (hard) for 6 dB S+N/Nwith 30% modulation at 1000Hz modulation.7 Close squelch. On the Comm radio push theSquelch knob in (close squelch).The Comm radio will have noaudio out.8 Get squelchsensitivity.On the HP8920:1. Set AMPLITUDE using the ↑up arrow until the SINADmeter reads squelch opens.2. Record AMPLITUDE assquelch sensitivity threshold.Will start to break at greaterthan:2 μV (-104 dBm).Note: Will be full open if signalis increased by 3 dB.