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Re: UO-22 azimuth-only system



On Fri, 30 Aug 2002, Jonathan Naylor wrote:

> what I did was to put an azimuth only system together with a vertically
> polarised 9ele yagi for the uplink with a fixed elevation of 30
> degrees. This meant that the 3dB points of the yagi occured at the
> horizon and at 60 degrees of elevation.

Here is my table from my http://www.ew.usna.edu/~bruninga/rotator1.html

EL  PCT CUM-% RANGE RNG-GAIN ANT-GAIN OVERALL-GAIN
--- --- ----- ----- -------- -------- ------------
10   32   32  3030     0       10         10
20   35   67  2440     2       10         12
30   17   84  1827     5        8         13
40    8   92  1460     6        6         12
50    4   96  1190     8        2         10
60    2   98  1020    10        0         10

Two important points.  Below 10 deg where 30% of all passes are, the
satellties are also 10 dB further away.  You dont want to give up ANY gain
on the horizon.  So point your beam at 10 degrees which gives full gain
from 0 to about 20 or more where you need it most.

As the satellite gets higher, it is closer and so any drop in gain above
40 deg is more than made up for by the satellite being 6 dB closer and
only being there 8% of all in-view times.

But if your terrain will not let you see down to the horizon (you have to
live on a hill), then instead of 10 degrees from the horizon, just mount
the beam 10 degrees above what you CAN see and you will have an optimum
system.

Hook it to a radio shack or any cheap rotator and there are almost 18
satelites you can pickup easily...  If you happen to have a THD7 or D700
then run APRStk (dos) and it will autotune the radio, auto configure the
internal TNC's, and auto rotate the radio shack rotator for a fully
automated satelite monitoring station for all the digital and FM
satellites.

And I am not "pushing APRStk" here.  I wish OTHER amateur satellite
tracking programs would provide the simple two-bit LPT1 port (right, left)
control for such simple ($20) rotator systems.  See the web page above...

We dont need full AZ/EL OSCAR class arrays and $800 rotator controller
systems for *ANY* LEO satellite.  And all of our satelltes are LEO's
except for OSCAR 10 and 40.  I wish more authors and AMSAT programmers
would recognize this and support the simple LEFT-RIGHT cheap-TV rotator
interface...  I think it would bring in more people to working the LEO
birds.

de WB4APR


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