[amsat-bb] Re: S band and Eagle: an appeal for more transparency (was Sband and Eagle: an appeal for a higher level discussion)

Edward R. Cole al7eb at acsalaska.net
Thu Sep 7 19:33:33 PDT 2006

Hi mode-S users:

I've read the comments (and their are quite a few...hint!), before adding
my opinions.

First of all P3E has a much closer (we hope) launch date and is much
further down the road in construction.  I'm guessing they didnot anticipate
that the WiFi generated noise floor posed a significant problem.  Perhaps
they can provide a larger mode-S ERP (I haven't compared spec's between the
original Eagle and P3E).  In any case, I am glad that P3E will fly both
mode-S and Mode-L...and then we will see the "truth" in the Eagle
engineering projections!

I wrote Bob McGwier (N4HY) soon after the referenced presentation was put
out as a web-link (I believe it was slated to be presented at this years
symposium, so was not intended to be pre-released).  But many of us read it
and discovered the major project changes that have been decided by the
design team (dion't you think major shifts in design ought to have some
public comment input ...i.e the users).

I proposed that the mode-S translator (S2) be flown as a contingency module
to the beacon Tx (S1, I believe) and tested in orbit as a linear
transponder.  If the noise floor issue is found to be a problem then the
module would just sit in standby (in case of failure of S1).  Bob rejected
that proposal.

Now, I'm hearing folks talk about the C-C Rider project but that has also
been scrapped (at least as a 5-GHz in-band transponder) according to the
presentation.  What I understood was that mode-C would be used for
digital-voice and video downlink with mode-S uplink.

BTW Eaglepedia does not reflect any of the recent design changes.  An
considerable portion is only outline with no content.  The general
membership will be challenged to follow the evolution of design (meetings)
in order to discover what is the current version of the project.  I guess
we will see in time how that Eaglepedia works out.

Unless the membership (read this as users...quite a few with recent AO-40
experience) can sway the design, I see big issues looming for Amsat-NA
"management".  I for one will use the mode-UV transponder on Eagle and
mode-LS on P3E.  Since I will be on social security by the time Eagle is
launched, I have little prospects for funding new mw bands.  But we will see!

one users opinion,
Ed - KL7UW

At 06:57 PM 9/7/2006 -0500, Stefan Wagener wrote:
>I have to agree with Bruce, however I don't take statements made by Bob
>McGwier (N4HY) (see below) for face value. 
>Quote by Bob(email to Amsat-bb on Tue 25/07/2006): "In upcoming journal
>articles and in Eaglepedia documents showing the detailed calculations upon
>which our statements are based" 
>Quote End 
>It is important that the data are presented, discussed, accepted or thrown
>The main problem with the whole discussion is that the majority of folks
>have NOT seen the data. In addition, if the data are as sound as they are
>portrait, why is AMSAT-DL not believing in them and is including S-band as a
>downlink. How is the discussion between ANSAT-NA and AMSAT-DL going on this?
>The lack of transparency is concerning and Eaglepedia is just an empty word
>if key documents and information is not published especially if it is
>available. Waiting for journal articles to come does not help. At the same
>time Eaglepedia still has the now "old" mechanical design specs and
>information on the S-band TX transponder available with no indication that
>both are obsolete.
>73, Stefan VE4NSA
>-----Original Message-----
>From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
>Behalf Of Bruce Robertson
>Sent: September 7, 2006 5:06 PM
>To: amsat-bb at amsat.org
>Subject: [amsat-bb] S band and Eagle: an appeal for a higher level
>....As I understand it, the Eagle design team have used standard
>predictions of
>801.11 usage to determine mathematically that by the time of launch the
>radio environment will simply not support reliable communications. I cannot
>imagine that they like these conclusions. Implementing new bands entails
>new risks, after all. But numbers don't lie (or shouldn't), and it would be
>a horrible disservice to all of us if they designed and launched a bird
>that was effectively mute at launch.....
>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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Ed - KL7UW 
BP40iq,  Nikiski, AK      http://www.qsl.net/al7eb
Amsat #3212
Modes: V - U - L - S

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