Signal disappears between 8pm and noon

[soundbets]

Anyone else ever encountered this problem?
At about 7:30 – 8:00pm every night, one of our dishes seems to lose signal completely. From 100% to nothing in ten minutes. Then at about noon, it comes back again!
I have checked the menu on the receivers this is affecting and everything is set how it should be, including the timers (I first thought maybe the kids had cracked our lock-out code and managed to change the timers to switch off – but that would have been too easy a solution!)
I called DTV but they had no idea, and just told me to check the cabling… but the cables are almost brand-new, and even if they weren’t this doesn’t seem like a cable problem to me.
During the “down” time when we check on the signal meter, we have zero signal on Satellites A & B, and still 96% on C. But obviously the system won’t work from just one satellite.
We have two dishes on the roof there - the uppermost one works fine, it is the lower one that cuts out. So I’m wondering if there’s any way that the upper dish is eclipsing the signal to the lower at certain points in the day. That would make sense except that a satellite is supposed to orbit WITH the earth and so stay static. All our receivers worked fine for the first month after we installed the second dish – and then suddenly this starts happening. It is not due to cloud cover & nothing is blocking the southern exposure...
Any ideas anyone? I'm stumped.

 

[meStevo]

Might just be certain environmental conditions and your equipment reacting to it, and this reaction ends after a very short period. Plastic on the LNB cooling off and contracting, something funky like that.

Either way, I just had odd problems w/ signal on my DVRs from only 1 sat, I couldnt explain it because standard receivers worked fine, but whenever id hook a DVR to any tap it wouldnt get signal from the 101. If you're not getting signal and your cabling is solid, I'd suspect the LNB. If you have a replacement or if both dishes are convenient to get to swap the LNBs and see if it follows it?

 

[mike123abc]

Well satellites are not fixed in the sky. They make figure 8s in orbit and wobble some.

Perhaps when it gets dark an owl perches on your roof...

 

[Neutron]

No they don't! Satellite TV satellites are in a geosynchronous orbit 22,500 miles high. They follow the Earth's orbit.

 

[boba]

Tell us what you have for equipment. It sounds like you have some temperature sensitive LNB that cools off at night and warms back up around noon. Do you have two separate satellite dishes each feeding a receiver or do you separate dishes combined to feed multiple receivers?

 

[slacker9876]

No they don't! Satellite TV satellites are in a geosynchronous orbit 22,500 miles high. They follow the Earth's orbit.

24,600 mi



Figues 8's ... certainly he was phucking with us...

 

[mike123abc]

No they don't! Satellite TV satellites are in a geosynchronous orbit 22,500 miles high. They follow the Earth's orbit.

When viewed from the ground they make figure 8s. They are not in a perfect orbit after all the moon and the sun are pulling on them too (not to mention the rest of the universe). They make course corrections regularly. That is why satellites eventually run out of fuel and go out of service. Even solar winds pressure the satellite out of orbit (the solar cells are like solar sails).

Satellites are kept in a .1 degree box assigned to them by the FCC, when they get close to an edge they are course corrected back into place. They also wobble and have gyroscopes to help keep them pointing at the earth. Perhaps if the earth were the only body in the universe they would stay fixed in place. But, the amount of movement is small compared to the distance and your dish cannot see it unless you are on the edge of a spot beam and you move in and out of it.

http://www.ctiinfo.com/SatControl/ComTrack/InclinedOrbitTutorial/satgeom5.htm

 

[soundbets]

Thanks everyone - it turns out it WAS the LNB. We switched it out and the problem vanished. Interesting education on satellites as well!

 

[meStevo]

Yay, gratz

 

[mick_murray]

24,600 mi



Figues 8's ... certainly he was phucking with us...

Not really in order to maintain orbit Satellites are continually flown to maintain position, the most common pattern is a figure 8 in an oblong box at the location. When peeking large dishes it is best done when the bird is in the centewre of the box. This is how ever not the case with a 18" dish.

 

[Neutron]

What I was saying was these satellite do not make a figure 8 like I'm picturing in my head. I'm thinking of how Sirius satellite radio operates, and their satellites do follow a figure 8 pattern. D* and E* are in geosynchronous orbits, so they follow a circular pattern relative to the Earth's rotation, not a figure 8. If they were in a figure 8 pattern you wouldn't be able to keep in a LOS to the satellites.

 

[mike123abc]

The satellite is not making figure 8s, just that when observed from earth it looks like they are making a figure 8. They stay in an assigned area .1 degrees of arc. Very small box. They just make course corrections to stay in the box. A standard pattern of course corrections designed to save the most fuel makes them look like they are doing figure 8s in the sky when observed from earth. They do not travel backwards, they just slow down in orbit and the ground gets "ahead" then they speed up and the ground gets "behind" they also are not exactly on the arc over the equator and drift back and and forth over the equator. The combination looks like a figure 8.