Satellite TV

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Satellite TV
« on: September 11, 2008, 09:03:18 AM »
Hello,

A question regarding satellite tv in the FET:

Some footage.

Satellite television, like other communications relayed by satellite, starts with a transmitting antenna located at an uplink facility. Uplink satellite dishes are very large, as much as 9 to 12 meters (30 to 40 feet) in diameter. The increased diameter results in more accurate aiming and increased signal strength at the satellite. The uplink dish is pointed toward a specific satellite and the uplinked signals are transmitted within a specific frequency range, so as to be received by one of the transponders tuned to that frequency range aboard that satellite. The transponder 'retransmits' the signals back to Earth but at a different frequency band (a process known as translation, used to avoid interference with the uplink signal), typically in the C-band (4–8 GHz) or Ku-band (12–18 GHz) or both. The leg of the signal path from the satellite to the receiving Earth station is called the downlink.

The downlinked satellite signal, quite weak after traveling the great distance (see inverse-square law), is collected by a parabolic receiving dish, which reflects the weak signal to the dish’s focal point. Mounted on brackets at the dish's focal point is a device called a feedhorn. This feedhorn is essentially the flared front-end of a section of waveguide that gathers the signals at or near the focal point and 'conducts' them to a probe or pickup connected to a low-noise block downconverter or LNB. The LNB amplifies the relatively weak signals, filters the block of frequencies in which the satellite TV signals are transmitted, and converts the block of frequencies to a lower frequency range in the L-band range. The evolution of LNBs was one of necessity and invention.

Satellites used for television signals are generally in either naturally highly elliptical (with inclination of +/-63.4 degrees and orbital period of about 23 hours, 56 minutes, 4.091 seconds hours(http://en.wikipedia.org/wiki/Synchronous_orbit)) or geostationary orbit 37,000 km (22,300 miles) above the earth’s equator.

The question:

At first, how is satellite television possible in the FET?

second: Why is it that me and a friend of mine (who lives 11KM away from me) have the satellite dish in almost (less than ¼% difference) the same angle towards the same satellite?

http://en.wikipedia.org/wiki/Satellite more footage
« Last Edit: September 11, 2008, 09:06:14 AM by IgnoranceIsStrength »

Re: Satellite TV
« Reply #1 on: September 11, 2008, 09:16:16 AM »
At first, how is satellite television possible in the FET?

It isn't.


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second: Why is it that me and a friend of mine (who lives 11KM away from me) have the satellite dish in almost (less than ¼% difference) the same angle towards the same satellite?

Because your dishes are pointed at satellites that are located 25,000 miles above the equator, so the difference in the bearing to that satellite is very small due to the difference in distance between the two dishes.

Re: Satellite TV
« Reply #2 on: September 11, 2008, 04:09:27 PM »
Satellites are not made to fly that low, it's just impossible with that design, so the 2nd answer is invalid.

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AmateurAstronomer

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Re: Satellite TV
« Reply #3 on: September 11, 2008, 04:53:42 PM »
Satellites are not made to fly that low, it's just impossible with that design, so the 2nd answer is invalid.

That low? That's near the high end of the spectrum.

"A Low Earth Orbit (LEO) is generally defined as an orbit within the locus extending from the Earth’s surface up to an altitude of 2,000 km. Given the rapid orbital decay of objects below approximately 200 km, the commonly accepted definition for LEO is between 160 - 2000 km (100 - 1240 miles) above the Earth's surface." Reference

"A High Earth Orbit is a geocentric orbit whose apogee lies above that of a geosynchronous orbit (@35,786 km, 22,237 miles). Highly Elliptical Orbits are generally considered to be a subset of High Earth Orbits."Reference

And as you already said...
"Satellites used for television signals are generally in either naturally highly elliptical (with inclination of +/-63.4 degrees and orbital period of about 12 hours) or geostationary orbit 37,000 km (22,300 miles) above the earth’s equator."Reference

Secondly, inclination on the 3 disk's I've helped family members set up was marked in 5 degree increments at best. Setting them up is 50% guesswork and 50% luck. If your friend who lives 7 miles away and yours are set the same, (except ¼% different) it might just be visual appearances.

And I'm sorry, but I honestly do not get what your question is on that point.

At first, how is satellite television possible in the FET?

It isn't.

Not true... I've heard theories that say they are blimps, or alternatively, that they are towers. 25,000 mile tall babel like towers.

Quote
second: Why is it that me and a friend of mine (who lives 11KM away from me) have the satellite dish in almost (less than ¼% difference) the same angle towards the same satellite?

Because your dishes are pointed at satellites that are located 25,000 miles above the equator, so the difference in the bearing to that satellite is very small due to the difference in distance between the two dishes.

This wouldn't be such a bad mark for flat earth, except that charting out all possible locations for this emitter on a flat earth based on the required direction and inclination posted in the manual received on purchase would show a line in the sky, instead of a point. Or possibly a disc, I'm not sure I'm imagining it properly.
Reality becomes apparent to the patient observer. Or you can learn a thing or two if you're in a hurry.

Re: Satellite TV
« Reply #4 on: September 11, 2008, 07:35:29 PM »
Satellites are not made to fly that low, it's just impossible with that design, so the 2nd answer is invalid.

That low? That's near the high end of the spectrum.

I'm thinking he misread that as feet instead of miles.
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