Astra 28, 2D fade out

[Huevos]

I've heard 101 (mostly stupid) explanations why this satellite fades out at certain times in fringe reception areas. What is the real reason?

 

[Analoguesat]

It can be for many reasons:

- increasing absorbtion of the signal due to dust in the atmosphere
- increasing absorbtion of the signal due moisture in the atmosphere
- the satellite moving around in its "location box" on a day to day basis which is enough to change the footprint by a tiny amount at extremne fringe locations
- at the equinoxes it will be switching to on board battery power as it goes into eclipse.

etc etc

 

[guest poster]

increased solar noise depending on where the sun is

reflected solar noise .. depending on where the moon is

lower power at uplink due to everyone putting the kettle on or air con (or whatever) at certain times of the day on the same grid as the uplink site...

We can induce solar outage on a certain under sized dish on certain ground locations on 26e on the weaker mbc tp at the same time every day in a given few months as the sun rises ... should also work in the west at sun set.

the outage = 15-30 minutes though

 

[Huevos]

- increasing absorbtion of the signal due to dust in the atmosphere
- increasing absorbtion of the signal due moisture in the atmosphere
- the satellite moving around in its "location box" on a day to day basis which is enough to change the footprint by a tiny amount at extremne fringe locations
- at the equinoxes it will be switching to on board battery power as it goes into eclipse.

OK, we can count out 1, 2 & 4 because this is a regular daily occurrence. And what about number 3? Is that going to be completely regular, day in day out, year in year out?

 

[Analoguesat]

Post EXACTLY what symptoms and times you see it - and your location (nearest reasonable sized town will do)

 

[Huevos]

38.5N, 0.5W. Symptoms: depends what gear is being used. Peak signal is about 3pm and weakest about 3am. 1.8m with a Pace 2600 will just about hold all vertical transponders all night. Any smaller dish and you start to lose them for part of the night (first they start to pixel and later completely disappear). With a Grundig box normally lose all transponders by about 8pm even with a 2.4m dish. But it's the same every day, year in year out, except if it is raining or cloudy which makes it worse.

Anyway the question is what is going on that makes this fade out so regular?

 

[guest poster]

Have you logged it for several years ... it should alter slightly through different times of the year a bit-

The sun outage on 26e on undersized dishes is regular over a period but alters through the year with the seasons... that is the sun getting behind the satellite we think... and that explains the brief outage compared to 2d. Also it can be difficult to measure it on larger dishes.

But 2d's evening outage sounds more like the setting sun in the west hitting the antenna of the satellite..? that is... 28e/ 2d in the east is 'aiming' westward to the UK and the setting sun is in the west low ... aiming in part back over the east at a similar low angle doing a bit of an unwanted 'solar' uplink..

Well... it sounds good ... even if it’s complete ‘/*&^%…

(could be bang on actually)

 

[guest poster]

hmm.. here's another one... sounds even better...

Years ago we used to do a bit of skip talking... bouncing radio waves off the ionized layer (the original DX ing) and talking to people around the world on power that couldn't get that far without bouncing off the ionized layer and back off the Earth & water ....

So what about the ionized layer when it comes to microwaves ?

I remember the characteristics change at night becoming better at reflecting certain frequencies than in the daytime.... and it had an 11 year cycle of high and low levels (I think) and it could go up at short notice days after large solar flares I think... and you'd get a call that the skips up and be talking to folk all over the place that night...

Is this another factor in the equation or is this the real answer that lies at the heart of the characteristics of daily fade and signal increase cyles on 2D & 7w on their respective fringes and behind why characteristics can change depending on location but on similar fringe signal levels?

Anyone up on this one...

 

[Huevos]

2d's evening outage sounds more like the setting sun in the west hitting the antenna of the satellite..?

I can't see that at all. The sun is in the southern hemisphere at the moment for a start, and even if it were related to solar noise the Sun is moving 15º per hour so the effect would be very short.

Could the satellite spin axis be slightly tilted? If so someone on the opposite corner of the footprint would have the opposite effect (strong at night, weak by day).

 

[pipino]

hi,
funny you saying that yesterday i didnt lose the signal from Astra 2D until 1:30 AM!!! ,something very strange because normaly i get total fade out from 11PM ,so i had total of 22 hours of full reception of Astra 2D vertical (10.847) ,i go for option 3 like Huevos...i wish we can reach that astra2d to move it a bit so we get 24hours of full signal .regards

 

[guest poster]

I can't see that at all. The sun is in the southern hemisphere at the moment for a start, and even if it were related to solar noise the Sun is moving 15º per hour so the effect would be very short.

What I was thinking was at the satellite getting a low angle from the sun... not the Earth's sunset horizon shadow. That low angle from the sun would persist at the GSO....

....and adding that to the ionized layer factor... could the solar noise not 'skip' at that low angle towards the satellite with the ionized layer funnelling the noise eastward at that low sun angle?... yes it would.... not sure on frequencies though... we used to use lower frequencies - very high didn't bounce as I remember but microwave can interact, possible breaking down and even cause ionizing.

Could the satellite spin axis be slightly tilted? If so someone on the opposite corner of the footprint would have the opposite effect (strong at night, weak by day).

Yes.. that does happen ...

7w here is the opposite but 2d & 7w have different characteristics depending where their being received.

 

[guest poster]

..........,i go for option 3 like Huevos...

I don't think huevos went for 3, it's not a regular daily cycle but it certainly is another variable that varies the signal not only at the footprint's fringe (good point AS) but also the position on the satellite cluster and where you have focused to.

 

[Analoguesat]

Of course its also possible its locally generated interference causing the problem - theres a big problem with C-band reception at the moment in the Middle East thanks to the roll out of wimax broadband.

Whilst its not going to be that at the Ku band frequencies, it could be any number of locally generated signals leaking into a system.

 

[Huevos]

it could be any number of locally generated signals leaking into a system.

For example what? This problem covers most of the south east of the peninsula. Also if it were noise why would people with larger dishes be less affected. Also, put a meter on it and there is no signal. The transponder just disappears.

 

[Analoguesat]

If you were in the UK Id say the police Tetra system or something similar.

People with bigger dishes will be less affected as they have more signal coming into the cabling in the first place.

Remember - the amplifiers on the satellites are only transmitting at about the power of a 100W lightbulb, it doesnt take much interference to disrupt the signal into nothingness.

By my reckoning 38N / 1W is somewhere near Murcia in southern Spain isnt it? You are right at the southern limit of effective reception there - infintessimal footprint shifts as the satellites swing around from day to day may well be enough to tip you over the edge of the "digital cliff". The satellites move around inside their box moving north and south a few miles every day. 2D reception conditions can vary immensely over a few miles - its been well documented over the years.

Stick a bigger dish up and many of your problems will go away

 

[Huevos]

By my reckoning 38N / 1W is somewhere near Murcia in southern Spain isnt it? You are right at the southern limit of effective reception there - infintessimal footprint shifts as the satellites swing around from day to day may well be enough to tip you over the edge of the "digital cliff".

Alicante. As you get further south Murcia - Almeria the signal improves. Even further south (Malaga) a 1.2m dish works fine.

 

[mich181189]

Ah yes. Basically, at night the ionosphere is refective, during the day it's transmissive, but it's frequency dependant. Above about 50mhz it's nearly always transmissive, hence why amsat satellites can be heard on 145/440mhz

 

[guest poster]

Alicante. As you get further south Murcia - Almeria the signal improves. Even further south (Malaga) a 1.2m dish works fine.

Alicante.... City noise ? and an airport ...? we've seen that before here for 7w.. it's not a daily cycle (some is though) but can add noise to worsen the cycle signal loss effect.

 

[Huevos]

Alicante.... City noise ? and an airport ...? we've seen that before here for 7w.. it's not a daily cycle (some is though) but can add noise to worsen the cycle signal loss effect.

Alicante is the name of the city and the province (same as New York, New York). I'm in the country here well away from any cable based interference. I've been watching "A Time to kill" for about an hour but now (00:25) it's starting to get unwatchable. Very frustrating.

 

[guest poster]

Ah yes. Basically, at night the ionosphere is reflective, during the day it's transmissive, but it's frequency dependant. Above about 50mhz it's nearly always transmissive, hence why amsat satellites can be heard on 145/440mhz

I don’t think it’s simple but there must be a noise/ signal loss factor due to ionization, it doesn't take much at the low levels of 2d or 7w on the fringe. Microwave can cause ionization too- that energy has to come from somewhere and the times match quite well. It can’t reflect too well because we’d be getting high frequency stuff bouncing all over the place… noise from the setting sun skimming the ionized layer sounds like it’s a viable part of the daily cycle noise equation for 2d & 7w fringe...




we're not going to change it though...