[amsat-bb] Re: 10mtr and Galileo

[Bill Ress]

Hi John,

Consider this.

1) Galileo operating frequencies are already co-located with existing ground
ATC radar systems. It has been indicated that the Galileo receivers will
need to consider these and other interference issues (like us) and build in
anti-jamming capabilities. Our GPS system upgrades are already working
further in this direction.

2) Amateur L-Band satellite transmissions from a single operator would
typically occur for short periods of time. A moving vehicle (car or plane)
with a Galileo receiver would quickly be moving itself away from an Amateur
transmission site. So statistically the chances for interference between a
fixed Amateur transmission and a plane or car have to be very, very small
and then only for a very short period. I've seen AMSAT comments about the
possibility of an Amateur L-Band satellite transmission bringing down a 747.
Don't think so.

3) I understand that interference could cause loss of acquisition lock but
that code reception would "free-wheel" until lock is restored. In other
words, already there appears to be a way of handling momentary interference.

3) Galileo, when (if) built out will employ 27 active satellites in a medium
earth orbit (23,616 km). I'm not sure how many satellites will be in view at
any one time but one must consider that not all visible satellites signals
will be interfered by an Amateur L-Band satellite transmission which will be
using rather directional antennas.

4) I understand that the P3E folks have already worked out a solution by
locating their L-Band operations in what will be a Galileo spectrum null. If
that is the case, then the P3E folks are really using some good "science" to
develop their satellite L-Band operations. Good for them!!

Hey - I'm not in the thick of it - but it seems there are some serious gaps
in communication between AMSAT-DL and AMSAT-NA even though we read about
glimpses of real technical exchange. I hope we're not falling for the NIH
(Not-Invented-Here) syndrome.

Regards...Bill - N6GHz


-----Original Message-----
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org]On
Behalf Of John B. Stephensen
Sent: Sunday, September 10, 2006 7:47 PM
To: jules at g0nzo.co.uk; amsat-bb at amsat.org
Subject: [amsat-bb] Re: 10mtr and Galileo


What bothered people is the fact that we need high power L-band uplinks and
the statement in the report that "there is the potential for most amateur 23
cm transmissions to interfere with Galileo unless the Galileo receivers are
designed and built to withstand it".

73,

John
KD6OZH

----- Original Message -----
From: <jules at g0nzo.co.uk>
To: <amsat-bb at amsat.org>
Sent: Sunday, September 10, 2006 23:37 UTC
Subject: [amsat-bb] Re: 10mtr and Galileo


> Just for the record, the first Galileo satellite has already been
launched:
> http://news.bbc.co.uk/2/hi/science/nature/4566264.stm
>
> Also there was a study made by the UK microwave group (the body
representing
> UK amateur interests above 1GHz), which makes interesting reading. It
> suggests that the signals from Galileo would have little impact on
> terrestrial/EME 23cms opperation. Obviously the conclusions woule require
a
> little re-interpretation, with respect to satellite based reception. But
as
> Galileo transmissions will presumably be aimed at the earth, so that any
> amatuer satellite will receive signals greater than that on earth, for a
> minute part of it's orbit, I would think that the conclusions drawn would
> still be valid. It's an interesting read:
> http://www.microwavers.org/papers/iaru/C5-13_Galileo.pdf
>
> Jules
> G0NZO
>
>
> >Speaking of allocations being taken away, I just can't fathom the AMSAT
> >decision to drop L-Band up because of the "Galileo Affair." Now that's a
> >decision based on "crystal ball engineering" and not fact. I've even read
> >that if Galileo ever was launched - and that appears in the latest press
to
> >be questionable" the US "would has threatened to shoot them down!"
> >
> >Regards...Bill - N6GHz
>
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