Garmin GNS 430 - Nose Bandwidth; Skirt Bandwidth; Spurious Response

Page 5-40 400 SERIES MAINTENANCE MANUAL
Rev. C P/N 190-00140-05
5.7.5.9 Nose Bandwidth
1. Apply standard glideslope test signal to the unit (-56dBm).
2. Find the AGC voltage and use it as a reference.
3. Vary the input signal frequency over the range of r17 kHz from the assigned channel
frequency.
4. Verify the input signal level needed to maintain the AGC reference voltage level does not
vary more than 6 dB.
 Input Signal Level Variance______ <6 dB @ +17 KHz
 Input Signal Level Variance______ <6 dB @ -17 KHz
5.7.5.10 Skirt Bandwidth
1. Apply standard glideslope test signal to unit at a signal amplitude of –93dBm.
2. Find AGC voltage and use as a reference.
3. Increase signal level to –33 dBm.
4. Vary selected frequency r132 kHz.
5. Verify the AGC voltage is less than the reference AGC voltage from step 2.
 AGC Reference Voltage______ dB @ +132 KHz
 AGC Skirt Voltage______ dB @ -132 KHz
5.7.5.11 Spurious Response
1. Tune the Glideslope receiver to 335 MHz.
2. Apply a 335 MHz signal at a –87dBm level.
3. Measure the AGC Voltage and use it as a reference.
4. Remove the test signal.
5. Apply an undesired image frequency test signal of 245 MHz with a 150 Hz signal, amplitude
modulated at 30%.
6. Verify the RF level of the undesired image frequency test signal of 245 MHz shall be greater
than –27 dBm to produce an AGC level equal to that of a desired frequency having a level of
–87 dBm.
 AGC Reference Voltage___________should be greater than -27 dBm image AGC
voltage