Garmin GNC 255A User Manual

190-01182-02 GTR 225/GNC 255 TSO Installation Manual
Rev. F Page 1-5
Table 1-5 COM Receiver Specifications
Characteristics Specifications
Classes C, E, H1, and H2
Frequency range
118.000 to 136.975 MHz, 25 kHz channel spacing
118.000 to 136.992 MHz, 8.33 kHz channel spacing
Headset audio output 100 mW minimum into a 500  load
Speaker audio output 12 W into 4 
Audio response Less than 6 dB of variation between 350 and 2500 Hz
Audio distortion Less than 5% at rated output power
Automatic gain control
(AGC) characteristics
Less than 3 dB of variation in the audio output from -93 to -13 dBm (power
absorbed by a 50  load)
Sensitivity
SINAD on all channels is greater than 6 dB when the RF level is
2 uV (hard) or -107 dBm (power absorbed by a 50  load) modulated 30%
at 1000 Hz at rated audio output power
Squelch Automatic squelch with manual override
Selectivity
6 dB BW is greater than +
7 kHz for 25 kHz channeling
60 dB BW is less than ±22 kHz for 25 kHz channeling
6 dB BW is greater than ±3.5 kHz for 8.33 kHz channeling
60 dB BW is less than ±7.37 kHz for 8.33 kHz channeling
Maximum audio output
reduction (offset
carrier operation)
11.2 dB

Garmin GNC 255A Specifications

General

Brand	Garmin
Model	GNC 255A
Category	Transceiver
Language	English

Summary

General Description

General Specifications

COM Specifications

Technical specifications for the COM transceiver functions.

VOR Specifications

Technical specifications for VOR reception.

LOC Specifications

Technical specifications for LOC reception.

Glideslope Specifications

Technical specifications for Glideslope reception.

Limitations

Installation Overview

Antenna Considerations

Cabling and Wiring Considerations

Installation Procedures

Equipment Mounting

Connector Pinout Information

Pin Function List

Detailed pin assignments for COM and NAV connectors.

Power, Lighting, And Antennas

Serial Data – RS-232

Post Installation Configuration and Checkout Procedures

System Configuration Overview

Mounting, Wiring, and Power Checks

Verifying installation integrity and power connections.

Configuration Mode Operations

Steps to access and navigate configuration settings.

Ground Checks (Configuration Mode)

Verification tests performed in configuration mode.

Ground Checks (Normal Mode)

Functional checks performed in normal operating mode.

Flight Checks

Procedures for verifying system performance in flight.

Software Loading

Appendix B GTR/GNC Data Format

Appendix D Interconnect Diagrams

Drawing List