Re: [amsat-bb] G5400 woes

[Bob Bruninga <bruninga@xxxxxxxx>]

On Sun, 11 Jan 2004 kb9cry@comcast.net wrote:

> ...There's nothing gained by placing a sat assembly way up in the air..

TRUE!... Entirely correct for AO-10, AO-40...    right on!

But unfortunately many HAMS think they need these huge arrays for LEO's
as well and there, exactly the OPPOSITE is true.  There, every LEO spends
33% of all ACCESS time below 10 deg elevation.  AND 66% of all access
times below 20 degrees!  Thus you need to see as close to the horizon as
you can.

What people should do is exactly as you describe.  Put the AZ/EL array
just a step ladder off the ground for AO-40.  Then buy a $60 Radio Shacek
TV rotator and a small beam and put that on top of the tower.  Mount the
single beam vertical polarization and tilted up at 10 degrees.  You will
hear every LEO satellite 98% of all access times. NO ELEVATION ROTATOR
NEEDED!  For anything above 40 degrees (8% of the time) remember that the
bird is 10 dB closer than it was on the horizon so the lack ot perfect aim
is insignificant.

DONT USE CIRCULAR for LEO's unless you have a polarity switching relay
either!  MOST of the time the signals are close enough to vertical to give
continuous good signals, and why give up 3 dB of gain most of the time and
the wrong polarity HALF the time when it is rarely if ever needed?
Just not worth the complexity.. (for LEOs).  Of course it is REQUIRED for
non LEO's (AO-40 is the only one right now...)

We need to make the general HAM poplulation understand that the CLASSIC
OSCAR array is only useful for AO-40 and no other bird.  (Its GREAT TO
HAVE, but not at all required and is far more trouble thatn it is worth
for the LEO's)...  We need to get the other 99 % of HAM radio operators
(who are not AMSAT savvy) to understand how simple it is to work the
LEO's.. with either a vertical AND LOW LOSS CABLE runs or better, with a
small Beam and TV rotator...

See my plot of LEO access times at each elevation angle on:

http://www.ew.unsa.edu/~bruninga/rotator1.html

de WB4APR, Bob

K9CRY continues:

> ...  For myself I'm glad I mounted my goo on a single tower section
> atatched to a base stub sunk in concrete.  I can reach the antennas from
> a long stepladder.  Now as far as rotators, I'm thinking of putting my
> spare G5400B on eBay and purchasing one of the new worm gear units from
> Alfa Radio; I have one of their Spids turning my new 40M beam and i!
>  t's real nice.  Check these out at: http://alfaradio.ca/
>
> Bummer dude; good luck and be safe.  Phil  KB9CRY
> ----
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