Well I am not sure what is intended to be on the L5 frequency in terms of power/link budget from the satellites but someone should tell the DOD etc that here in Europe at least there are many ( ie tens of ) civilian air traffic control radars on and around 1250 MHz. Their peak powers are in the gigawatt range and although the highly directional dishes tend to point upwards a bit, they radiate lots towards the horizon. Also it should be noted that many of them are not located at airports but on tops of hills/ mountains to give area coverage. Not the sought of RF environment that would suit weak signal handheld GPS receivers running on a couple of AA batteries with a patch antenna IMHO! BTW before anyone else brings it up I have to declare a non AMSAT interest in these frequencies- I am also involved in planning ATV repeaters in the UK and most of these have inputs around the 1245-1250 frequencies. - and yes we do co-exist with the radars! The 1250 possibility first came to my notice at the IARU Region 1 Conference in Tel Aviv in '97 but I had not been able to find out any further information up to just now. If any more detailed information is available/emerges I would be most interested in it! 73's to all Graham G3VZV -----Original Message----- From: Santillo, John <SANTILLOJ@pcmail.systems.gec.com> To: AMSAT BB <amsat-bb@AMSAT.org> Date: 14 April 1998 16:23 Subject: L-Band >Hello all. The below information came out of the Hudson Division >Loop newsletter. Althought it doesn't impact satellite uplink >frequencies directly, I thought it might be of interest to the group. > > > > *** From "The ARRL Letter" 4/10/98: The ARRL has learned that >the second civilian frequency for the Global Positioning System >(GPS) could wind up within Amateur Radio's secondary allocation >at 1.2 GHz. A decision on whether the new, second frequency will >be 1205 or 1250 MHz is expected to be made in August. An >allocation at 1250 MHz could mean the end of Amateur Radio in the >band 1240 to 1260 MHz. The Amateur 23-cm band runs from 1240 to >1300 MHz. > In February 1997, the Departments of Transportation (DOT) >and Defense (DOD) announced an agreement assuring civilian GPS >users of a second frequency--referred to as L5 and considered >essential for critical civilian GPS uses. According to a DOD >news release, the White House Commission on Aviation Safety and >Security, chaired by Vice President Al Gore, "called for the >establishment of a second civil frequency as part of a broader >program to maintain US leadership in aviation and satellite >technology." For more information, see >http://www.defenselink.mil/news/Feb1997/b022797_bt095-97.html.