[amsat-bb] Re: Galileo interference on L band

[Bill Ress]

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 at 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