On Tue, 18 Sep 2007 18:06:25 -0500, Mike Spera
wrote:

Well, as many of you can remember, I have posted my saga about
intermittent reception problems with my Garmin GPSMAP 396 from day one.

The same reason my 196 loses reception, from Garmin's support database

"
Question: Why is my GPS losing satellites in the middle of my flight?
Answer:

Portable GPS units have the ability to experience loss of satellite
reception as a result of RF interference caused by a variety of
sources. These sources can be as simple as a portable MP3 Player 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.

Radio Frequencies That May Jam GPS Receivers.

Transmit 131.285 and 121.186 Receive

Narco MK 12D/E Com 810/811, Nav 824/825 Com 131.220 and 119.285 Nav
115.464 and 109.672

King KX 155/165 Com 131.820 and 119.885 Nav 116.128 and 109.564

King KX 170/175 Com 122.285 and 130.186 Nav 113.651

Collins Microline Com 132.720 and 120.785 Microline Nav 116.028 and
109.464

Notes: KX 155/165 transmitting on 118.15 ws 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.
Last modified on: 08/30/2007

"