[amsat-bb] Re: Phase 4 versus Eagle
kl7uw at acsalaska.net
Fri Dec 14 10:43:29 PST 2007
I have direct personal experience with this when I was a TVRO
installer up here in Alaska.
Before the mid-1980's TV-satellites pointed their antennas at mid
America around Kansas - Nebraska. Due to Alaska being not only at
the far northern fringe but also western edge of the beam, signals
were down around 6 to 10 dB (from memory). This meant that to
receive the signal in Alaska one needed at minimum a 12 to 14 foot
dish. IN Barrow (Lat=70) it took 16 to 20 foot dishes pointed a few
degrees above the horizon (7-deg max due south). As time went on the
satellite industry re-pointed some of the satellites to better favor
Alaska and Hawaii resulting in being able to use 8 to 10 foot
dishes. Today we get ku-band sat-TV with the use of a 30-inch dish
(you use an 18-inch dish in the lower-48). We find that we need a
1-1.2 m dish to overcome rain/snow fading, though.
OK how does this relate to P4? For far-north or far-south stations,
it will require careful ham station antenna location that can see a
clear low horizon elevation angle and probably more antenna gain to
overcome being on the fringe of the satellite antenna
"footprint". If the sub-satellite (straight down) position on the
equatorial orbit is too far east or west of one's local longitude,
there will be no view above the horizon for the extreme latitude stations.
This will have no technical cure. So hopefully the orbit positions
that can be obtained will be favorable to the maximum population. I
would expect P4A and P4B will ride to mid-America and European
positions. The Pacific sat probably would be the last launched if
one were trying to reach the maximum ham population centers (only logical).
So you can see why Alaskan satellite operators are hoping for the
launch of P3E and Eagle. Otherwise we may be in for a long wait till P4C!
PS: I'm taking the liberty of assigning the designations P4A, P4B,
P4C (not AMSAT terminology).
Following the saga with interest - and hope!
73, Ed - KL7UW
At 08:50 AM 12/14/2007, Andrew Glasbrenner wrote:
>I noticed the new release of SATPC32 12.7 includes Intelsat
>spacecraft in one of the keplerian/satellite options. You can scroll
>through them and get an idea of the possibilities and range of
>footprints. Real life performance will be, as Bob suggests,
>dependent on our antenna pattern. Other services are usuable from
>the poles, such as Inmarsat, given enough gain and a clear horizon.
>MTI uses this as a selling point for their phone with the 4 ft
>dishes we S-band types are so fond of. So we might work fairly well
>out to the edge, again, dependent on the antenna.
>73, Drew KO4MA
> >From: Robert McGwier <rwmcgwier at gmail.com>
> >We do not know the answer yet. Our request is for multiple payloads,
> >covering with subsat over Atlantic, Pacific, and Central U.S. We would
> >need one over the Indian Ocean to cover the 2 pi radians of the equator
> >with antenna pattern. The north and south pole would be left out so I
> >am sure the emperor penguins and polar bears would be upset!
> >Simon Brown wrote:
> >> Where would this GEO be positioned? Even rough information would be
> >> interesting.
> >> Simon Brown, HB9DRV
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Ed - KL7UW
BP40IQ 50-MHz - 10-GHz www.kl7uw.com
144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w
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