distance,from satellite to earth?

[Turok]

Hello!
on my 1000.post here,i want to bring some answers into the questions,how the distance,from earth to satalillite will vary,during,the difrent seasons!

in winter,the cband recption,of weak channels,is much better,then in summer time,i dont think ,that "only"the coldnees is the mainreason for it,on indian dordashan transponder for example, i have good signal,when it temprature is 7 minus.when it 5+ or more then it will interupts the picture!

but back to the distance,
its vary up tp 5000 km,some one told me around one month ago,i can imagine this,that the satelite,is in winter time,"only" 33500 km away from earth ,instead of normaly 38000!

but is it on every satelites ,the same distance ,that vary?
i dont think so,but i think its the same prinzip,then distance,form earth to moon,in summer time,in the full moon nights,it is also shorter,then in wintertime,when the moon looks smaler!

okay,now iam waiting,for your (electro)physical input

could this 5000 km,distance,that the satellite is nearer to the earth,could affekt the signal quality,in a better result?
espasaly in out of foot print reagions,also in kuband!

to years ago,we have a very intresting situation,in kuband,on thaicom,on the mtv thailand transponder,this is switched off in the meantime!

it was posible,to receive this channel,here in central europe with a 2,40 m dish,

only of the coldness,or the lower dinstance,i dont know?
,mabe in thailand whould also work,to reveive european satelites,when it whould so cold,then in europe,i dont know,but this fact,that is pirciply also works,in kuband,when the terms are convenient ,is very intresting!

in brazil,with the 8 meter dish,dr dish told,it is only posible,because of signal reflection from earth atmoshpere!
that breaks the signal,and reflect it stronger !

 

[Analoguesat]

The broadcast satellites are geostationary - they dont move at all . (Well actually they do move a little - each one has a box roughly 30 miles across which is its space to float around in)

Difference in signal strength do vary during the year (most noticable in extreme fringe reception conditions) This can be caused by

- the satellite switching over to internal batteries when it goes into eclipse at the equinoxes
- water vapour or rain in the atmosphere especially on extreme slant paths though a lot of atmosphere
- lnb's getting too hot or too cold causing the internal oscillator to drift slightly.

etc
-

 

[Turok]

Hello! good Morning!
thank for your first input
yes i understand this fact,but the earth,and the moon,is also always,at the same postion,but the difrent,from earth to moon,is not always the same,there is a 3. unkown part,in the gestacionary puzzle,that i dont understand!.@ the moment!
maybe the earth,and the moon,also drift alot,because,there is no earth gravitation in the universe?

 

[Topper]

Turok the moon does not come in to the calculation at all, it has no bearing on the satellite transmissions that we receive on earth, the only thing the moon influences are the tides and the Pendle Witches

 

[Channel Hopper]

Turok

Analoguesat's answer to you did include 'etc.' which would cover quite a few additional variables, almost all of whch would mean an improved signal at your location.

The affect of low temperature on the dish is most likely the reason for improvement, on a large sectional metal dish, the reflector assembly may have more of a parabolic shape to it, and the distance of feed horn to reflector surface could be nearer to the manufacturers specification. Additionally the time of assembly of the dish could also be a factor, if it was installed in winter, it will now be at the same shape when the dish bolts were tightened.
Other factors are humidity within the feed will be lower, the thermal noise of the LNB will also have improved, and the noise generated from the ground and other nearby objects will be lower, giving a better carrier to noise ratio.

To be honest there is no single 'main' reason for changes in reception characteristics of satellite signals, with the exception of the temperature change across the whole link, but even that would mean alterations of each part of the link budget. You also have forgotten that the uplink of a particular transmission may also be affected through seasonal change, and the broadcaster hasn't taken any measures to adjust the signal to compensate.

I would disagree with you that the distance of the satellite to the earth changes between summer and winter. If this was the case the position of the satellite would have to change, something that doesn't happen with geostationary ones.

 

[Turok]

Thank you Channnel Hopper,for your intresting deep analyses!

i think the dish size,from the uplink itself,is also resposible for the signal strenth,not only the beam focus alone!
espasaly on 68,5 e in cband,we have many difrent beams,indian dordashan transponder,also a problem to receive in africa ,i read here on board!
sometimes here sometimes not,but most of the indian channels also sends on 28,5 east,but not all!

i take the moon only for an accord example,because his distance,from moon to earth,is not always the same over the year,and difrent from,the place,on earth where you watch from!

in greece for example,in summer nights,the moon is much more bigger,then here in central europe,the phase,that the moon here,is like a big brighting eye,is here relatifly short!

i cant explain this,why its everywhere difrence,it could be only a quesiton of the distance itself,in my opinion!
maybe iam wrong i dont know

 

[Analoguesat]

The moon's distance does change because its orbit isnt actually circular - its elliptical. This week the full moon has been the closest to the Earth for 15 years:

_http://news.bbc.co.uk/1/hi/sci/tech/7779294.stm

 

[Channel Hopper]

Thank you Channnel Hopper,for your intresting deep analyses!

i think the dish size,from the uplink itself,is also resposible for the signal strenth,not only the beam focus alone!
espasaly on 68,5 e in cband,we have many difrent beams,indian dordashan transponder,also a problem to receive in africa ,i read here on board!
sometimes here sometimes not,but most of the indian channels also sends on 28,5 east,but not all!

No, the uplink antenna and associated equipment is designed to transmit to the satellite
1)at a specific minimum signal level,
2)to overcome all weather conditions,
3)work in the case of a failure of any components, and
4)minimise outside jamming of the signal.

This is why the uplink station consists of very large dishes, full redundancy HPA's and pressurised feed systems.
Additionally the downlink from the satellite itself (at a different frequency to the uplink) as well as the dish direction, can be adjusted by the uplink station to follow a specific footprint above a country, or continent.

The lower

 

[Turok]

Hello!
ohh,i now the reason now why i cant sleep at night,its always the same when full moon is outside,now seems to be the magnetic field is much stronger now!

around 2 years ago ,there was a intresting moon darknees,that goes around 45 minutes ,was very intresting,i look out the window,with my sony 800 x zoom digicam,the moon looks complete red,like in the movie,the dark side of the moon


,so longer,you look into the moon,so easyer,you can imagine,the vulkan mauntains on it,some say,when you know,the location,and weather is good,you can also see the satelites,with normal eye,without any telescope from earth!

but i look and look,and never see any bird!

maybe,we split the moon part,of this topic,into the meeting zone

 

[Low Profile]

Temperature has a huge effect on noise. The only reason that it's generally overlooked is because in the main it's difficult to do anything about. If you put an external (outdoor) antenna on a spectrum analyser you can see the noise level rise during the day (with the sun). Burying the coax cable, and cooling the LNB may help.

 

[FlyerUK]

Hello! good Morning!
thank for your first input
yes i understand this fact,but the earth,and the moon,is also always,at the same postion,but the difrent,from earth to moon,is not always the same,there is a 3. unkown part,in the gestacionary puzzle,that i dont understand!.@ the moment!
maybe the earth,and the moon,also drift alot,because,there is no earth gravitation in the universe?

not quite true, the difference in distance between earth & moon varies, since the moon is in an elliptical orbit, currently it's at its closest for 15 years. The sats are, however, geostationary, their distance varies very little.

 

[dago]

m8, radio signals are greatly effected by temperature, inthe north
pole radio signals travel much easier than at the equator. that is
why super cool computers are far more efficent.
regards.

 

[julian_1234]

m8, radio signals are greatly effected by temperature, inthe north
pole radio signals travel much easier than at the equator. that is
why super cool computers are far more efficent.
regards.

I don't think the temperature directly effects their "ease" of travel.
The reason you get more range is probably there's more chance of getting inversion layers that can duct the signal, and also you're likely to get fewer people locally using the same frequency (and hence less interference).

 

[Channel Hopper]

And then there are those living on a flat earth ......