[amsat-bb] S-Band and Eagle

ANTHONY JAPHA tjjapha at earthlink.net
Tue Sep 12 14:18:26 PDT 2006

There have been so many thoughtful comments on the S band question that
it's been fun to follow the thread.  I'd like to chime in.

I bought S band gear just before AO40 went south.  Not a lot of equipment,
just a W7LRD dish with helix, a K5GNA converter, and a few odds and ends. 
Unfortunately, I never got to put them on the air.  Now I try out the
converter on AO-51when the mode is right.  I live in Manhattan, operate
portable, and have a fairly decent QTH to get maybe a 100 degree window. 
Mode V/U on AO-51 is a breeze with an HT, and FO-29 provides the occasional
DX QSO using a pair of FT817s and an old 20 watt 2 mtr. amp.

S-band here is nearly hopeless.  I live in a census tract that contains 10
city blocks.  There are 15,000 people in 9,000 households.  I would not be
surprised to find that 75% of those households had some sort of 2.4 Ghz
device!  The bird can be directly overhead, but only the rare station pops
up out of the noise for a few syllables at a time.  Using an Arrow ant. for
435 Mhz., by contrast, much is heard on both FO-29 and AO-51.

That is my experience.  It is an anecdote, to be added to the many others
that have been shared.  I would be shocked if a satellite designer paid
much attention to it if he had some more aggregate data on which to base a
design decision.  It's a shred of evidence, no more, no less.  Even a cub
reporter shouldn't write about it without doing some research into what
others are experiencing and whether my experience squares with what
informed people and the data suggest.  For one thing, my QTH probably isn't
typical, to say the least.  The designers of Eagle probably aren't hung up
on making sure that users in my position should be able to use all the
bird's modes.  They probably don't design for the superstations either. 
The job is to make the bird useful to the greatest number of possible users
given the budgets they face (money, power, size, etc.).

The evidence I've seen in these exchanges seems to favor the designers by a
large margin.  They have cited their evaluation of the available data
regarding the present and future use of S band.  Are there data to the
contrary?  The fact that some stations can make it through a tough QRM
situation isn't very convincing.  It is the great majority of stations that
should be able to use the bird.  

I have a couple of concerns.  Is the emphasis on making the bird accessible
to very modestly equipped stations (like mine?!) going too far?   The
bird's potential use in emergencies sounds farfetched to me.  Maybe if
we're down to a choice between the bird and a semaphore!

I'd also like to know much more about the ground equipment required for S/C
mode.  How will it interface with existing equipment in the shack?  Are
these new pieces of gear add-ons to existing transceivers or do they stand
alone?  What functions to they perform?  Sorry, but I'm not up on digital
SSB and CW as you can see. 

Finally, is enough known about U/V to tell us now what ERP and receive
capability will be needed?  That is, how big will the antennas need to be?

Thanks for all the work being put into this by the design team.  If Eagle
is going to fly any time soon, we've got to let them get on with it.

Tony, N2UN
LM 183 

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