C band Question ?

[1ADAM12]

Does anyone notice a little difference betwen SQ in daytime and after dark?

 

[pendragon]

While we sometimes refer to the satellites as geostationary, they do not stay exactly in the same position with respect to the earth. Satellite operators are assigned "boxes" to keep their satellites inside, and to conserve fuel, the birds wander around over a one day period. I believe a decent sized C-band antenna can see these effects, but I haven't done an analysis. Technically you should align your dish only to satellites when they are at "center-of-box", which many operators publish, but this isn't as critical for FTA as those with really big dishes. But most of those can track dynamically anyway.

 

[meinename]

Yes I noticed it alot when I was starting out.

Middle of box seems to be 8am-10am on the West Coast for most orbits that I aim for.

The 7am to 10am Work Block works out best for me to peak dishes.

Doesn't mean I'm right, but it works so far on Ku and I'll be putting that theory to the test this next week with a 10 footer.

Right now the 8.5 footer with a 4DTV likes to move the peak signal for all satellites 10 clicks east or west depending on time of day.

 

[Mr Tony]

depends on the channel and what size dish you have

If the signal is strong at noon it probably will be the same at 9:00 at night.....but weaker signals do fluctuate

 

[1ADAM12]

Yes I noticed it alot when I was starting out.

Middle of box seems to be 8am-10am on the West Coast for most orbits that I aim for.

The 7am to 10am Work Block works out best for me to peak dishes.

Doesn't mean I'm right, but it works so far on Ku and I'll be putting that theory to the test this next week with a 10 footer.

Right now the 8.5 footer with a 4DTV likes to move the peak signal for all satellites 10 clicks east or west depending on time of day.

Thanks for that.

That is what I see also.

Almost not noticable 1 - 2 % SQ.

Kinda wondered if it had to do with ionization of the F1 layer, I've not seen this on KU.

 

[B.J.]

Yes I noticed it alot when I was starting out.

Middle of box seems to be 8am-10am on the West Coast for most orbits that I aim for.

The 7am to 10am Work Block works out best for me to peak dishes.

Doesn't mean I'm right, ....

You're not right. Every sat orbit is different, plus there are very few satellites where you could see the orbital variations with normal sized dishes. For most sats, the variation isn't going to me more than a tenth of a degree, and you aren't going to see that affect your signal. There are lots of computer programs you can use, or write yourself that will allow you to find the equator crossing times, which would be the daily episodes of interest. Years ago, NBC used to use a sat that had a sizeable inclination, and I used to use an orbital prediction program to predict the equator crossings, and I'd start seeing the signal appear when the sat was a bit more than a degree from the equator, and it would improve to perfect reception as it crossed the equator, then become unwatchable again after it was more than a degree off in the other direction. I later wrote my own program to predict the crossings. These programs will also show a slower, not daily, drift in longitude, which generally would be more than the north south daily drift for the stationary sats. Usually the sat controllers just let the sats drift for a few days, then kick them back to where they're supposed to be.
It used to be that people who watched G10r would complain about interferrence from the nearby Echo-9 sat, and it was interesting to see how this longitudinal drift would correspond to the complaints on the forums.

EDIT: Over the years, I've seen dozens of posts about how reception either improves at night or gets better at night, and I've also observed these effects myself. I never have completely rationalized all these effects, but I'm sure that they are usually due to things like temperature, humidity, solar noise, and terrestrial noise, and even interferrence from other occasional video sat signals rather than orbital effects.

 

[1ADAM12]

EDIT: Over the years, I've seen dozens of posts about how reception either improves at night or gets better at night, and I've also observed these effects myself. I never have completely rationalized all these effects, but I'm sure that they are usually due to things like temperature, humidity, solar noise, and terrestrial noise, and even interferrence from other occasional video sat signals rather than orbital effects.

Thanks for that observation.

 

[pendragon]

I've certainly seen very small reductions in SQ with increased humidity and heavy cloud cover on C-band. It's possible in some climates such variations are roughly diurnal. It is also possible that thermal expansion/contraction in the dish, mount, pole, etc. may have an effect on pointing, too. However I have become slowly suspicious that there may be more happening.

Several months ago I was watching a multi-hour high rate feed on my 3m from over the pond on a satellite that barely reaches Colorado. At the start I had the barest of link margins. Over the next few hours it deteriorated and started breaking up, but I found I could improve things by bumping the controller a click east or west. It got worse, and out of curiosity I went to the dish and gave it a crosstrack nudge first one way and then the other. I got the hang of it and eventually it started heading back the other way. I probably should have grabbed the orbital elements, but didn't. The cloud cover was clear the whole time and our weather station showed no significant variation in temperature or humidity.

I do see consistent, but very tiny variations on a daily basis for satellites where have the 3m mechanically locked for long periods of time. The curious thing is the times for the peaks/lows change over days and sometimes abruptly. Different satellites are not on the same schedule. The 3m has a HH motor and its step size is about 0.05 degrees. I can measure similar, miniscule signal variations by stepping it by one click, so I believe the antenna pattern is not constant over a 0.05-0.10 degree range.

So far my observations are purely anecdotal. While a little interesting, this hasn't qualified yet as worthy of a thorough investigation. Admittedly I'm only speculating at this point.

 

[delta_charlie]

Hi all, I think it may also have to do with the ionosphere. There is a huge difference between day and night operations on the low ham radio frequency. I think there might be some effect on the high satellite frequency. If you want to learn more Google "ham radio ionosphere"

Later, DC

 

[Scott Greczkowski]

Might also be seeing some TI which is different in the day then it is in the night.

 

[jimbofta]

Well...I would suggest that at least part of this puzzle is temerature-related. LNBs work more efficiently, the lower the temperature.

I used to record 'banned' Beavis and Butt-head episodes on a KU feed from MTV Canada, and the best recordings were ALWAYS in the dead of winter. Ahhhhhhhh, the good old days when there was a lot of in-the-clear programming!

Jimbo.

 

[Iuplink]

You're not right. Every sat orbit is different, plus there are very few satellites where you could see the orbital variations with normal sized dishes. For most sats, the variation isn't going to me more than a tenth of a degree, and you aren't going to see that affect your signal. There are lots of computer programs you can use, or write yourself that will allow you to find the equator crossing times, which would be the daily episodes of interest. Years ago, NBC used to use a sat that had a sizeable inclination, and I used to use an orbital prediction program to predict the equator crossings, and I'd start seeing the signal appear when the sat was a bit more than a degree from the equator, and it would improve to perfect reception as it crossed the equator, then become unwatchable again after it was more than a degree off in the other direction. I later wrote my own program to predict the crossings. These programs will also show a slower, not daily, drift in longitude, which generally would be more than the north south daily drift for the stationary sats. Usually the sat controllers just let the sats drift for a few days, then kick them back to where they're supposed to be.
It used to be that people who watched G10r would complain about interferrence from the nearby Echo-9 sat, and it was interesting to see how this longitudinal drift would correspond to the complaints on the forums.

Correct on the NBC bird part. They used to do a lot of early am satellite shots on GSTAR4 which was an inclined orbit bird, which "wobbled" in a figure 8 pattern. We would call the satellite access center to find out where exactly the bird was, whether it was at the top of the arc or at the bottom and then aim our antenna accordingly, manual peaking. The problem was if it was on the top of the figure 8 and heading down I had to repeak 2 or 3 times to keep up with it before the morning liveshots. As of last checking SBS 6 is at an inclined orbit somewhere near where it used to be positioned.

 

[B.J.]

C...As of last checking SBS 6 is at an inclined orbit somewhere near where it used to be positioned.

According to the latest 2 day old keps, SBS6 is inclined, but it is no longer in a geosync orbit. It looks like it's been parked out about 230 miles outside the Clarke belt. and it's longitude is drifting about 4.6 deg per day, so I'm guessing that SBS6 may never be used again.

 

[Inno]

Regarding temperature relating to signal strength, I have not noticed it much in my area, maybe because we do not get more than 3-4 weeks of sustained really high temperatures (80° and above).......this year maybe only a week if that. My feeling is that there are so many factors such as layers of atmosphere, clouds, TI, precipitation even if it is not visible to us.......so many things we can not see between us and the satellites that there are sure to be changes on a regular basis. What I used to tell customers when I was installing was something like "there is a lot of space between us and the satellites that I can't even imagine and they have an effect on your signal strength". I never took much time to figure it out except that if signal was marginal, increase dish size.
I have however noticed temperature playing a roll with UHF TV reception although it may have something to do with other factors at play with the changing seasons. In the middle of winter the UHF reception is always much better than any other time of the year.........now with everything digital I should notice a slightly higher signal strength I'm guessing.

The talk about satellites in inclined orbit etc. is very interesting, thank you for adding those bits of information.