Hi Dave,
That's a very good valid point! You see, its the technical issues like this I'd like to see debated and considered, not considerations made for the "unknown or uncertain."
If the L-Band antenna size needed causes compromises for some other more primary mission requirements, then the decision is easy. L-Band goes and I can live with that.
The future uncertain state of frequency allocations is one that I would have difficulty designing for today. "ALL" of our satellite allocations up to 24Ghz are on a "secondary" basis. That makes them fair game for interference from and to primary users and changes by regulatory bodies.
With that "uncertainty" in mind, do we jump up to 24GHz for our transponders where we're primary. Not a real good idea but we'd sure eliminate all this WiFi, Galileo discussion - at least until some commercial endeavor jumps on 24 GHz with a "killer" money making application and we're back to the "uncertain" all over again.
So when it comes to our below 24 GHz frequency allocations we should design for mitigations (co-existence) not abandonment.
But, it appears that the Eagle team, according to Rick's last post, will have L and S capabilities consistent with the overall mission requirements and that's a positive thing.
Regards...Bill - N6GHz
-----Original Message----- From: David B. Toth [mailto:ve3gyq@amsat.org] Sent: Friday, September 22, 2006 9:59 AM To: Bill Ress; AMSAT BB Subject: Re: [amsat-bb] Re: Galileo interference on L band
At 02:54 AM 9/22/2006, Bill Ress wrote:
Yes - those are admirable desires but we can't engineer for "unknown"
future
events. It just bogs us down with worry that we might not make the right "guess." Instead, as I stated before, base decisions on the engineering facts as we know them today (available technology, size, power, space, resources, user needs, etc.) and let the future bring on whatever it has in store for us.
If you can make arguments that L-Band won't work because of system engineering constraints or the mission objectives we have before us today - I can live with that. But lets take this Galileo "cloud" off the decision process.
Bill: I think one of the problems still is how to get a large enough L-band gain antenna on the satellite so that the ground station antennas don't end up being huge. If I got that wrong, perhaps Bob McGwier and the team could correct me. If we cannot get a high gain system with reasonable beam-width (steerable vs. non-steerable) on the satellite, then the ground station antenna might be unwieldy compared to the higher frequencies.
Again, I may have misunderstood this point, so I could easily stand corrected.
Dave