Sorry -- I've been away from home on business while the latest flack occurred under the general topic heading "Galileo interference on L band".
First off, just so everyone can read the presentation materials that we used during the San Diego meeting, please take a look at the EaglePedia web site at http://www.amsat.org/amsat-new/eagle/EaglePedia/index.php/San_Diego_Digital_.... Then take a look at my presentation "Frequency Considerations for Eagle" at http://www.amsat.org/amsat-new/eagle/EaglePedia/uploads/1/19/Microwave_Freq_.... You will see (my slide 6) that I present the arguments pro/con about why (IMHO) L-band is at jeopardy as a long-term uplink band.
Let me add a few comments about why I'm so concerned. The reason that the Galileo E6 (functionally the same as GPS L2, and overlaying the amateur 1260-70 MHz uplink allocation) is important for some uses is that it, when used in combination with the primary 1.57± GHz "L1" frequency (which is what all your cheap hand-held GPS receivers use), can be used to correct the ionospheric errors; the ionosphere adds upwards of 10 meters to the pseudo-range for each GPS satellite. Because of geometric factors (expressed quantitatively in VDOP), this can in turn yield errors in height of up to about 30 meters. [The WAAS and EGNOS signals provide some correction for these biases to the few meter level, but cannot be relied on during severe ionospheric storms.]
There is a lot of factual evidence that when dual-frequency geodetic GPS receivers (costing ~$25,000 -- hardly cheap!) have been used in proximity to terrestrial amateur L-band stations, the GPS performance is seriously degraded. I direct your attention to several reports on the topic:
* Must reading -- GPS/GLONASS vs L-band digipeaters (Also see GPS World, Oct.2002) (warning contains numbers and equations, as well as uncomplimentary comments about digipeaters) http://elib.uni-stuttgart.de/opus/volltexte/1999/278/pdf/278.pdf#search=%22g... * Amateur and Radar QRM reported at a 1999 technical meeting: http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/33rdmeeting/Presentati... * A tutorial that shows how interfering signals can affect a spread spectrum GPS rcvr (caution -- contains more numbers): http://www.rin.org.uk/SITE/UPLOAD/DOCUMENT/Vuln-Owen.pdf#search=%22gps%20ama...
Even though US amateurs may feel that Galileo is a "European only" problem, read carefully Rick's (W2GPS) comments -- in his real life for many years he was a VP with ARINC (the people who worry about standards in the airline industry) and was on many FAA and ICAO committees that decide on airline safety.
Also realize that the Europeans are absolutely determined to develop their own GNSS (Global Navigation Satellite System) call Galileo -- in part because they don't really trust a system that depends on the US Military, and in part because they see a giga-Euro business opportunity for the EC. Who knows how long it will survive, but the Russians have their competing GLONASS system. And both the Chinese and Japanese see that they need to enter into the GNSS race is they are to be world-class technical competitors.
We, the Eagle technical team, have never said that L-band won't work NOW or 5 years from now. But our vision for Eagle is that when the first one flies 4-5 years from now, we want it to be a useful resource for at least a 10 year lifetime. We are very concerned about making a several million dollar (after you count the volunteer builder's blood, sweat & tears) investment only to have it blown away right after launch by the GNSS cartels just because we picked L-band to be anything like a "primary" uplink.
73, Tom