Why is my GPS Losing Satellites in the Middle of my Flight?

Portable GPS units have the ability to experience loss of satellite reception as a result of Radio Frequency (RF) interference caused by a variety of sources. These sources can be as simple as a portable MP3 Player or cell phone used for in flight entertainment to a ground based air traffic control radar antenna on an airport. When these devices are powered on and are in close proximity to the portable GPS or antenna, the GPS may lose satellite acquisition as a result.

Another common source of RF interference is aircraft communication and navigation radios. When certain radios are tuned to a specific frequency there is the potential for enough RF interference to be released that the Portable GPS unit will experience loss of satellite reception as though the signals were being jammed. An article in the Aviation Consumer, dated February 15th, 1994 has outlined a list of aviation communication radios and frequencies that may cause a portable GPS unit to lose satellite reception in the aircraft. This information is listed below.

Notes: KX 155/165 transmitting on 118.15 was shown to jam an external mounted antenna. Narco MK 16 tuned to any 115 or 109 Nav channel was shown to jam a hand held GPS. Narco MK 12D/E and Nav 824/825, if not wired with memory keep alive, will default to 115.5 MHz in the active channel and will jam any GPS receiver.