[amsat-bb] Re: Why do the amsats get more and more complex?

Bill Ress bill at hsmicrowave.com
Wed Sep 20 12:21:57 PDT 2006

Hi Bob,

Thanks for your response which is starting to focus on the pitch you really
need to make, and which you can defend (it's down toward the end!).

You state another "what if" and not a "fact."

"What will happen if the Galileo goes up is that no European airport will
allow a commercial jetliner to land without the Galileo system.  This
will inevitably lead to this basic system being in world wide use for
navigational purposes."

But consider the "fact" that all commercial airlines are currently using the
US GPS system and a MLS (microwave landing system) that uses around 5 GHz.
Our GPS system is also going through additional studies regarding issues
with potential interference and these are NOT Amateur transmissions. Since
the Galileo is intended to focus on "personal" and "for profit"
applications, (check out their web site and mission statements), I can't see
commercial airlines scraping their current working systems in favor of an
uncertain Galileo system. If they do - it will be many, many years down the
road. So I can't buy your commercial airline "fear" scenario. Again an
argument based on "fear" not "fact".

Again, I keep repeating that Galileo recognizes the potential for
interference (again - see their web site). We are but one of many potential
sources of interference. In "fact" to date they have not even included us in
their list of potential interfering sources (again see their web site).

You state "The receiver manufacturers will not want to build high quality,
expensive front ends
to filter out powerful emissions that could bring an airplane down. They
will choose the path of "clean the bums out" and they will win."

You can't be serious Bob? You know darn well any airborne receiver used for
aircraft navigation will be designed to be as bullet proof as possible.
Again read the Galileo web site for their comments about interference where
they state their system will "detect, identify and mitigate" potential
inference. Is this lip service to sell the system or a real desire to build
a solid system?

You state:

"So your idea is that we should spend $10,000,000  of donated money on
the back of prayer that Galileo will not force us off our band when we
KNOW it will be viewed as a safety of life service and that we will
overload the front ends of the receiver in the (admittedly very rare)
cases where the airplanes are in our emitter beams?  No one can be that
naive to believe that even the slightest possibility of interference
will be allowed."

No Bob, I'm saying that your reason for dropping L-Band should be based on
technical considerations not "fear" of what might happen.

You state:

"We cannot use L band for the advanced communications package anyway
because we do not want to increase the antenna size for the ground
user.  We want to accomodate CC&R restricted users with a 60cm (2 foot)
dish.   The L band feed required, being dual band with C band (say)
makes this infeasible."

Bob - now you talking the RIGHT ARGUMENT! Given a variety of technical
considerations, available money, available current, space etc., these are
the justifications you need to emphasize.

Get this "weak" (in my opinion) Galileo argument off the table and focus on
we what we know to be the "real science" that you are already bringing to
the project.

You stated another good technical "fact" when you said:

"Here is a fact you have not taken into account. The advanced communications
package  needs 10 MHz not a few tens of kHz but I have already discussed why
L band is not usable for the system (ground and
space) we are attempting to accomodate.  That has nothing to do with
Galileo or the loss of L band.   In fact,  if we can fit the antennas on
the spacecraft,  I see no reason we shouldn't include an L band receiver
and we should drop it into the Galileo null.   The issue will be
coordination with our AMSAT-DL friends and partners to mitigate
interference issues.  These should be rare indeed if we achieve our
target orbit for Eagle and they achieve their target orbit for P3E.  The
birds will be many degrees apart almost always when L band will be

Way to go Bob. Technical arguments! That's what I want and your hitting on
them now.

Bill - N6GHz
AMSAT #21049

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