RE: [amsat-bb] Eagle disappointment - No

[Robert McGwier <rwmcgwier@xxxxxxxxxxx>]

Wayne wrote:

If the power budget can only support one high-power transmitter at a time, I
think it's reasonable to have V-band transmit near perigee for 100 MA's and
S-band transmit near apogee for 155 MA's.  The switch point is at roughly a
squint angle of 30 degrees.  It would be nice if both transmitters could be
on for a short time so that V-band-only operators could make contact with
S-band-only operators.


I write:

If there is nothing but omni antennas on for "Mode B" (U to V band),  then
"squint angle" does not mean very much and people are overreacting.  The
satellite is small.  It is not physically possible to get a high gain
antenna on for two meters.   Remember that once you have stabilized the
satellite with respect to the stars, the spacecraft tends to remain in that
orientation and is subject to small perturbations that will have to be
corrected for with magnetorquers.   I think almost all of the reaction I
have
seen so far makes the assumption that we will have smaller half power beam
width antennas (such as the ones on AO-40).  The size alone dictates we will
not.  The designers are doing you a great favor by stating ahead of time
that when the path loss is smaller (closer to earth), is when we will use
the mode that will have poor antennas.  Remember, they don't hate U to V
(Mode B) users.  They hate what physics says they must do.  Finally,
I wish we would stop saying we will replace AO-10 or AO-13 since we clearly
will NOT since both of those satellites had a reasonably large frame
and could get gain on two meters as a result.


Finally,  I have thought, since the very first time I heard the concept
that it was, and continues to be, a mistake to do a satellite design of
this type without a launch in mind.   If we can't get a Russian or
ESA ride, there will be no ride to elliptical at all since we are not
carrying propulsion.

Bob


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