Astra 2D evening fading in Spain

I

Indasol

Member
First Post!! - Has anyone properly (i.e. in terms of dBs) plotted the variation in signal level of the Astra 2D signal in Spain? I’m sure many are familiar with Stefano Ferrairo’s excellent work on the variation in 2A/2B North transponders http://idd009rc.eresmas.net/, has anyone plotted similar variations for 2D? Also, and this may have come up elsewhere in this forum, do we have an accepted scientific explanation for the phenomenon?
 
Indasol said:
First Post!! - Has anyone properly (i.e. in terms of dBs) plotted the variation in signal level of the Astra 2D signal in Spain? I’m sure many are familiar with Stefano Ferrairo’s excellent work on the variation in 2A/2B North transponders http://idd009rc.eresmas.net/, has anyone plotted similar variations for 2D? Also, and this may have come up elsewhere in this forum, do we have an accepted scientific explanation for the phenomenon?
Click to expand...

I dont know about plotting footprint but the phenomenon is simply equated to a torch beam and variable shaped reflectors. The earths magnetic field, which is not even or consistent also has some efffect, I would think.
Regards
dave
 
Dave
I don't think I understand the analogy you're making. If we assume that the satellite is the torch, if it's in geostationary orbit why should the surface area it illuminates vary? It should be noted that these variations are predictable in so much as the time at which the signal falls below the receiver threshold is the same every day to within a matter of minutes, as is the recovery of signal level.
 
There have been a few threads attempting to fully explain this signal variance. Some of it can be explained by daily satellite repositioning causing a footprint wobble and general orientation of solar panels, whilst there may be an element of power conservation during certain periods also.

I seem to remember a couple of other potential causes being discussed, but can't bring them to mind.
 
It can be seen from S.Ferrairo's research http://idd009rc.eresmas.net/ that the 2A North and 2B North variations are almost exactly equal and opposite. These 2 satellites reside in the same constellation so any earthly variables can presumably be ruled out. What is involved in the repositioning process?
 
Don't know, but I'm sure there is someone on the forum who does.
 
I would say if, you were near the fringe for your
dish size the weather would play the most
dominate role.
 
Hi

If you go to, http://www.astra2d.co.uk/, you will find lots of information. Interesting reading under, "Footprints", "The Astra 2D Forum" and "old message board".
I was led to believe, many moons ago, that the satellite horn antennas were specially shaped or a number linked together to produce a footprint, that was my understanding.

gmbp:-righton
 
Schnuffi said:
I would say if, you were near the fringe for your
dish size the weather would play the most
dominate role.
Click to expand...
Schnuffi, The weather certainly does play a significant part in received signal strenghth and consequently the duration of the 'window' for which reception is possible. However the point is that given stable weather conditions the signal still varies throughout the day, in a pattern that is repeated to within minutes day after day. Astra 2D reception falls to it's lowest level around 11pm here on the Costa Blanca and begins to recover around 2am, but I haven't been able to plot the 24hr variation due to a lack of suitable test equipment. Has anyone else? Incidentally 2D is weakest in the evening, whereas 2A North is weakest late afternoon, so I don't think it's related to nightfall.
 
gotmybuspass said:
Hi

If you go to, http://www.astra2d.co.uk/, you will find lots of information. Interesting reading under, "Footprints", "The Astra 2D Forum" and "old message board".
I was led to believe, many moons ago, that the satellite horn antennas were specially shaped or a number linked together to produce a footprint, that was my understanding.

gmbp:-righton
Click to expand...
Yes, I've seen this website, and very good it is to. No conclusive answers to this particular issue that I have seen though. I think your correct about the formation of the footprint, however why does the shape or/and relative position of the footprint vary throughout a 24Hr period? Incidentally the published footprints from SES Astra are very theoretical in my opinion, in reality I believe there are a multitude of spikes/dips and sidelobes to the pattern which explain why a 1.5m dish is OK for 2D in Marbella but a 2.4M is required in Alicante.
 
The only prolem with the map that I can see is that it overestimates the signal strength in the centre of the beam.

From personal experience I know that a 60cm dish is a bit on the small side for good reception of 2D in Southern France in the Vaucluse department. I suspect that other areas within the centre might be similarly overestimated.

PaulR
 
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