[TowerTalk] Snow and rain attenuation
jimlux at earthlink.net
Tue Nov 1 08:47:38 EST 2005
At 11:28 PM 10/31/2005, VR2BrettGraham wrote:
>Any dish not pointed by somebody who knows what they are
>doing & with a spec-an could be as much as 1 dB down from
>where it could be.
>Dish size on the ground is always too small - despite filings
>to ITU for coordination of the bird in the first place.
And there you have the basic conflict in high gain antennas. If you make
it big enough to have the link margin you want, then you've got to point it
too accurately, which raises the installation cost.
There ARE solutions, of course.. you can make an electronically steered
phased array for fine pointing, for instance. (This is what I've been doing
for the past two years at work, except for transmitting video back to earth
from Jupiter or Mars)
So far, though, nothing is cheap enough for the exceedingly cost sensitive
world of consumer electronics. I personally find it amazing that they can
mass produce LNBs with 20K noise temperatures at 12 GHz and sell them for $50.
That whole industry (as Brett can tell you) calculates everything down to
the penny. Since they subsidize the receiver and dish/LNB cost, that
factors in. "Do we make the dish 2" bigger, and spend $0.50 per unit for
aluminum on millions of dishes, or do we add another square meter of solar
panel to the bird." I used to work with a Set Top Box manufacturer, and
they agonized about pennies: "Do we really need that bypass capacitor there?"
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