Garmin GDL 88 Pilot's Manual

Also see for GDL 88: Installation manual

Garmin GDL 88 Pilot's Manual Manual pdf 14 page image

2-4Garmin GDL 88 ADS-B Transceiver Pilot’s Guide 190-01122-03 Rev. C2.2 Automatic Dependent Surveillance –Rebroadcast (ADS-R)Because it is not required that ADS-B In capable aircraft be able to receiveADS-B data on both the 1090 MHz and 978 MHz data links, a means to get datafrom one data link to the other is required. ADS-R is the rebroadcast of ADS-B databy FAA ground stations and provides this service by taking data from one link andrebroadcasting it on the other. For example, two aircraft are in the service volumefor a ground station, and one transmitting on 1090 MHz and the other 978 MHz,the ground station will retransmit the data from each aircraft on the other link toensure the two aircraft can “hear” each other.Figure 2-4 ADS-R Operation - FAA IllustrationThe GDL 88(D) is capable of receiving ADS-B traffic reports directly on a 1090MHz data link in addition to traffic reports and FIS-B weather uplinks on the978 MHz data link. This allows the GDL 88 to directly receive all ADS-B positionreports from aircraft in the vicinity guaranteeing the most complete traffic pictureis available to the flight crew without relying on being within ground stationcoverage and ADS-R to provide this complete picture.