Re: [amsat-bb] RE: Leo Class stations

[Jesse H Morris <w4mvb@xxxxxxxx>]

Hi David and the Group,

When I first got back on the air about 7 or 8 years ago I used a 2M
antenna arrangement of a 14 elemment crossed yagi fixed at about 15
degrees elevation, a 5 elemement quad fixed at about 45 degrees elevation
and a HB version of the "Egg Beater".  As the satelite went up in
elevation I just switched transmit antennas.  It worked great on RS-10
and RS-15.  It was fixed phase but it even worked well on the uplink for
FO-20/29 most of the time.   An elevation rotor was necessary for the
downlink on these birds however if your wanted to really enjoy the
operation.  I solved that problem, as many did, with a $60 TV rotor
mounted sideways.    In addition, some sort of phase switching was also
necessary for relaible operation.  I built several antennas during three
or four years of testing and I found that I really did not need circular
polarization.  Switching between vertical and horizontal polarization
worked just as well.  (Yeah I know you get a 3db advantage when the
circular polarizations line up properly but how often does that happen
and who can tell the difference anyway on a LEO pass?)

The point is that getting everything to work is a lot of fun (for me
anyway) and if you wait until you get everything perfect to start the
process you may never get on.  I don't learn much with success but my
failures in the past several years have taught me plenty - and provided
me with a lot of enjoyment.  Even with simple equipment you can get on
one of the birds and as you learn more you can get better.  My first
RS-15 contact was made with a 5/8 wave whip antenna sitting on a fence
post and 50 watt of power from my HB 2M transverter. It took Dave, G4CUO
and I the entire pass to exchange signal reports and grid locations - but
we did it!  I still use an old Yaesu FT-107M for a transmit IF and
transverters for 145 and 435 uplinks.  I guess that leaves me out of the
"one true rule" operations.

I can't help but believe that there would be a lot of operational
interest in new RS style LEO birds but I also recognize that there is not
much interest in building such satellites.

Just my two cents worth.

73 de Jess - W4MVB


On Tue, 24 Feb 2004 22:14:02 +0000 David Carr <dc@dcarr.org> writes:
> Steve,
> 
> I'm currently am in the midst of experimenting with various LEO 
> antenna 
> arrangements to expand my portable operation.  One idea that I 
> currently 
> like is the idea
> of using a simple az-only TV rotator (available at RadioShack,etc 
> for 
> ~$60) to rotate a small vertical beam.  The beam is tilted upwards 
> slightly with respect to the horizon.  This provides good gain for 
> the 
> lower elevation parts of the pass, and as the bird gets up higher 
> its 
> increasing signal strength compensates for the beam's reduced 
> sensitivity at higher elevations.  The relatively low gain of the 
> system 
> makes pointing requirements not all that stringent.
> I believe Bob Bruninga has described this setup in the past.  You 
> might 
> find some relevant info at 
> http://web.usna.navy.mil/~bruninga/rotator1.html
> 
> Hope this helps,
> David Carr
> KD5QGR
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