[amsat-bb] Re: S band and Eagle: an appeal for a higher level discussion

Bruce Rahn brahn at woh.rr.com
Fri Sep 8 18:13:20 PDT 2006

Tom Clark, K3IO wrote:
> We considered the RFI environment carefully (see my CSVHFS paper for
> details) as it would exist 10 years from now. Why 10 years? Well, it
> will take us 3-4 years to fly Eagle, and then we hope it will last and
> be useful for at least a decade, so a 10 year forecast seemed about
> right. In that time frame, many of us (me especially) feel that the
> European Galileo GNSS (Global Navigation Satellite System, i.e. GPS)
> (and possibly similar systems being designed in Japan & China) will have
> prime DOWNLINK signals overlaying our 1260-1270 MHz UPLINK band. The
> signals being sent down may well be deemed critical for "Safety of Life"
> services; it is not unlikely (double negative used intentionally) that
> administrations may cancel out our L-band uplink so those "damned Hams
> can't cause an A380 with 500 people on board to crash!". Since weight,
> power and volunteer engineering talent are all finite resources, we came
> to the conclusion that it was not prudent for us to invest in an L-band
> uplink.  C'est la vie.
Sigh....a bit of paranoia here? 

Galileo should be a bit more immune to jamming than our current GPS system due to the signal structure they will employ.  But, they are still going to have to make provisions for unwanted signals.  

It doesn't take much to knock GPS off the air...there have been a number of documented cases of aircraft loosing GPS tracking due to terrestrial interference.  The threat of interference by a regulated body such as amateur radio is far less than the threat presented by an uncontrolled group of terrorists.  Navigation system designers, be it GPS or Galileo, are going to have to count on interference (jamming) as a fact of life and make provisions for it.

Perhaps yanking the amateur allocation is one of those steps, but that would only address a minority problem...and leave the other, far greater threat, unchecked.  

Regards -- Bruce 

Bruce Rahn

Wisdom has two parts:
1.  having a lot to say; and
2.  not saying it!

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