[amsat-bb] Re: Eagle Satellite Design

Bruce Robertson broberts at mta.ca
Sat Sep 9 10:22:02 PDT 2006

Quoting Luc Leblanc VE2DWE <lucleblanc6 at videotron.ca>:

> On 9 Sep 2006 at 6:21, Rick Hambly (W2GPS) wrote:
> .
> > 
> > If, after considering all the information that is now available, you
> still
> > feel strongly that we are doing a bad job then ask yourself not what
> > can do for you, but what you can do for AMSAT. > Subscription
> settings: http://amsat.org/mailman/listinfo/amsat-bb
> Your clients eg:your actual and former members nearly unanimously voices
> their opinion about 
> maintaining an S band downlink on Eagle as previously planned by you by
> the way. Do you feel 
> strongly that you are doing your job ignoring them?

This is a long letter, and though it replies to Luc, it is not specifically
directed at him. I respect Luc as a long-standing contributer to this list
 and an experienced satellite radio operator who has dug my lousey signal
out of the mud many times. However, in my opinion, the statement above is
not an accurate description of the situation. Many of us are willing to be
convinced by the science, and I, for one, have heard nothing convincing
from the pro S-band group and some pretty discouraging numbers from Bob B.  

What the board faces in this discussion is some members who, according to
the research of their engineers, want two mutually exclusive things: a
satellite design that will support the defined uses; and an s band
downlink. To my mind, if the research is right, the Board is making the
only sensible choice: to plan to build a working bird without the s band
downlink. It seems silly to build a bird that has a S band downlink and
doesn't work, that's why there are people who think they'd rather do other
things with their lives. (Of course, The horns of this dilemma may be
avoided if the research is wrong.)

> Answer your own question first don't blackmail your membership. You are
> a grown up and you are able 
> to take you own decision... when you already feel the pressure from your
> membership it takes only 
> an open mind to adjust the plan not bad faith.

Thus as I see them, the statements of other Board members do not constitute
extorsion (which I assume Luc means when he writes 'blackmail'). In fact,
I'd say there is good evidence that this board has put together an
excellent Design Team: they've focussed well on the purpose of the bird in
its future use and, in the process, questioned all assumptions. I worry,
though, that the reaction on this list will inspire them to delay
announcements of partial results. We want an open process, under peer
review; let's act like peers.

One idea came to me this morning as a means of exploring the situation on S
band right now. Setting aside Eagle for a moment, this will help some of us
get an idea if our set-ups will work for P3E and ESEO, which, if they both
work, will give us plenty of S band linear action.

 If we degrade our links to AO-51 by an appropriate amount, we could
simulate working a S band HEO satellite (ok, in FM mode :-). I'm not sure
what the gain of the antenna on AO-51 is, and I believe the power out is
3w, but perhaps that's max and not in use. Based on Bob's formula, the
improved path loss will, I think, be on average (40000km /2000km )^2 = 400
or 26 dB. 

So, assuming that the HEO has higher gain antennas and better power out,
just for fun, let's put some 20 dB resistor pads in the right place (help
me here: it would need to be between the antenna and the downconverter,
right?). Actually, the right amount of RG58 could probably do the trick. We
could even have a sim-HEO night on AO-51. Someone in Ohio could pretend
they're in New Zealand :-)

73, Bruce VE9QRP

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