Garmin GTR 225 Installation Manual

Also see for GNC 255: Pilot's guide

Contents

Garmin GTR 225 Installation Manual Manual pdf 38 page image

GTR 225/GNC 255 TSO Installation Manual 190-01182-02Page 4-6 Rev. B4.7.2 GTR/GNC Unit Insertion and RemovalIt may be necessary to insert the hex drive tool into the access hole and rotate the drive toolcounterclockwise until it completely stops in order to ensure correct position of the retention mechanismprior to placing the unit in the rack. The GTR/GNC unit is installed in the rack by sliding it straight in untilit stops, about 3/8 inch short of the final position. A 3/32-inch hex drive tool is then inserted into the accesshole at the bottom of the unit face. Rotate the hex tool clockwise while pressing on the left side of the bezeluntil the unit is firmly seated in the rack.To remove the unit from the rack, insert the hex drive tool into the access hole on the unit face. Rotatecounterclockwise until the unit is forced out about 3/8 inch and the hex drive tool completely stops. Thiswill allow the unit to be freely pulled from the rack.Be sure not to over tighten the unit into the rack. The application of hex drive tool torque exceeding15 in-lbs can damage the locking mechanism.4.7.3 Unit ReplacementWhenever the GTR/GNC unit is removed or reinstalled, verify that the unit powers up successfully.4.8 Antenna Installation and Connections4.8.1 COM AntennaThe GTR/GNC unit requires a standard 50  vertically polarized antenna. Follow the antennamanufacturer’s installation instructions for mounting the antenna.The antenna should be mounted on a metal surface or a ground plane with a minimum area of18 inches x 18 inches. Refer to Section 3.2.1 for installation location considerations.The antenna coax cable should be made of RG-142B, RG-400 or a comparable quality 50  coax.Check for insertion loss and Voltage Standing Wave Ratio (VSWR). VSWR should be checked with an in-line type VSWR/wattmeter inserted in the coaxial transmission line between the transceiver and theantenna. The VSWR should be inserted as close to the transceiver as possible. When rack and harnessbuildup is performed in the shop, the coax termination may be provisioned by using a 6-inch inline BNCconnection. This would be an acceptable place to insert the VSWR. Any problem with the antennainstallation is most likely seen as high reflected power. A VSWR of 3:1 may result in up to a 50% loss intransmit power.