[ 27 September 2004: Message edited by: Mike Keenan ]

cricket

Right?

[ 28 September 2004: Message edited by: Albireo ]

quote:

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Originally posted by Coyote:
They're in the sky.
cricket
Right?
Technophobes, present ignorance.

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"Sky?" So, I know these things are up there. However, my dish is aimed barely over the hill south of my house. There are places around here which can't get a satellite signal, because of that hill. Are the satellites high enough to have line of sight over the curvature of the earth all the way to the poles? When they are not even high enough to clear a hill?

We need a forum 'Everything you sorta wanna know, but are too lazy to look up yourself

[ 28 September 2004: Message edited by: Tackaberry ]

quote:

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Originally posted by Doug:
People in the far north probably do have a problem getting satellite signals if they happen to be north of a hill.

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quote:

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Originally posted by Tackaberry:
So how many satellites are up there? If they are restricted to such a small band, how come they never crash into each other?

We need a forum 'Everything you sorta wanna know, but are too lazy to look up yourself

[ 28 September 2004: Message edited by: Tackaberry ]

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The "band" isn't that small. I don't know its exact size, but I would guess that it is several thousands of km wide. Also, more importantly, geosynchronous satellites have fixed positions relative to each other, as long as they are roughly at the same height relative to Earth. This is true of any satellite, by the way. Satellites closer to Earth orbit faster, satellites further away will be slower. Satellites in geosynchronous orbit turn around the Earth with a speed equal to that of the Earth's rotation.

[ 29 September 2004: Message edited by: Surferosad ]

Is it a parabolic dish, or a spherical one? (bear with me).

Parabolic dishes have the received square in the middle of the curve of the dish, so the signal reflects off the dish and is focused there. But, a parabolic dish is a difficult shape to manufacture. A spherical dish is easier to manufacture, but won't focus all the signal to a point directly in front of the dish. It will, however, focus the signal properly if it's set so the incoming signal 'strikes' the dish a glancing 'blow'. That's why (AFAIK) that ExpressVu and similar satellite TV dishes have the receiver slightly below the 'dish', instead of directly in front of it. This would make more sense if I could sketch you a drawing..

So your signal is probably arriving from somewhat higher than you thought it was just from looking at where the dish is 'pointing'.

quote:

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So how many satellites are up there? If they are restricted to such a small band, how come they never crash into each other?

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Lots!

There's even alot of space junk up there in orbit (space pollution!) that all has to be tracked to make sure things don't bump in to each other. Every geosynchronous satellite has its own "parking space" so to speak and "who gets what" is all decided by international agreements.

Not all satellites are in geosynchronous orbit either. (Although communications satellites have to be). Some satellites are in various eliptical (sp?) orbits.

There are also weather satellites, research satellites (monitoring pollution and things like that), military spy satellites that take pics of the "other guy's" war toys, even ham radio satellites (I've played with some of these...they're really cool!)

And of course there's the International Space Station which is a large enough object that it can be seen with the naked eye when it's doing a pass (although not in urban areas!).

I once saw the old Soviet "MIR" space station doing a pass over southern Ontario. MIR was a pretty large object as satellites go. The ISS is even larger.

Satellites in this net, I think there are 24 now, rise and set, but it is rigged so that at least three of them can see any point on earth all the time. Your GPS receiver does an automatic triangulation on the ones it can "see", and computes the data from them.

All the ocean radio aids to navigation are being phased out, and soon Decca, Loran and other systems will be but a memory for us old salts to yarn about. If you ever had to do a Loran fix by hand, well, God bless you.

VLF surveys measure the secondary field given off
rock and ore bodies as a percentage of the primary field transmitted from the nearest military VLF substation, which could be as far away as Cutler, Maine, for example. Various mineral deposits have their own distinct VLF "signature." Mag surveys measure the intensity of the earth's magnetic lines of flux as well as the angle of dip they make with respect to the earth. Again, an ore body will alter the norm or baseline reading of the surrounding country side. Power stations, water, electrical transmission lines and Canadian taxpayer funded oil and gas pipelines to carry our raw materials south can appear to be an ore body or mineral anomaly when graphed.

Of course, exploration companies now take advantage of multi-spectral satellite and radar exploration techniques, thanks to taxpayers ...again.

[ 08 October 2004: Message edited by: Fidel ]

The site has detailed information about most of the satellites. It's fun to go looking for the ones placed in the wrong orbit.