Inclined Birds ..

[Vipersan]

OK got your attention with the header ..
We all wish our birds were inclined ...err ..very sexist ..
;)
Seriously though ..
The figure 8 movement of an inclined satellite is a tricky enough thing to follow accurately ..
But my question is this ..
Given that the bird 'describes' this movement with presumably a loop above and below the true arc ..
..and that the degree of inclination is described as say 4 degree inclined ....ie ...+ or - 4 degree above and below ...making a total of 8 degees of shift..
Is the figure 8 described .. face on ..in which case it appears to shift laterally as well ..
..or edge on in which case it should appear as though moving only in a vertical dimension ...
..though occasionally being further away or closer to the observer..
rgds
VS

 

[Lazarus]

And there I was watching Julia Bradbury on Countryfile .....................

 

[Vipersan]

Sorry to drag u away Gordon ..

I've spent the day ...trying to track Astra 1C and 1D @2 deg East ..
No easy task ..but not impossible ..
Here are a few caps ...from the 1.8m fitted with 'the mole'..

I also caught 4 dog track feeds ..sadly all encrypted ..
Hove
Perry Barr
Oxford
& Kinsley ..

Did however get a couple of clear caps to post from ITN feeds..
These birds are _far_ from inactive..
rgds all
VS

 

[Vipersan]

Here's a thought ...
Since a laptop or preferably a pda can produce Infra Red signals and emulate button presses of a remote control ..
How about having a program running on a pda (adjustable time interval ...and reverse point)
..For example the programmed pda could be set to issue a single click East command every 4 minutes or so ..in this case go East would Elevate the dish one click ....at a pre defined interval ...ie the top of the figure 8 loop ....it would reverse ...sending 'decline' pulses/go-west ...and again reversing at the bottom of the loop ..
You effectively let the pda control the V-box and therefore in control of automatically tracking an inclined Satellite..
Has this been done already ?
On the cheap that is ..??
Its certainly worth thinking about.
rgds
VS

 

[fergyc]

Sorry to drag u away Gordon ..

I've spent the day ...trying to track Astra 1C and 1D @2 deg East ..
No easy task ..but not impossible ..
Here are a few caps ...from the 1.8m fitted with 'the mole'..

I also caught 4 dog track feeds ..sadly all encrypted ..
Hove
Perry Barr
Oxford
& Kinsley ..

Did however get a couple of clear caps to post from ITN feeds..
These birds are _far_ from inactive..
rgds all
VS

The dog feeds are all for Sky, when that bird's been on the arc I've caught an unencrypted one. When my new 80cm comes in I'll use the zone 2 to get the feeds. Someone on LJ's site uses it for the 3pms for the Football League show, it has all the Championship games ect. He marks the elevation scale with tipex at 3pm and uses that.

 

[Vipersan]

..thanks Fergyc ..
Wouldn't it be cool though If my idea for autotracking an inclined bird could be used ..
You would of course need an actuator driven dish with 2 directions of movement ..
rgds
VS

 

[Rick]

It's possible to strap a couple of LNB's to the side of the focal one and adjust until they are set for reception at required times. The inclined birds coming in as on offset. This can be done with a motorised as well.

The Triax Multi LNB brackets mounted vertically work really well for it on a 40mm LNBf, using black premium or eco lnb's let's you get them spaced 2 degrees on a TD110

 

[Vipersan]

Good Idea Rick ..
Sadly not for me though ..
As mounting anything permanent on the 1.8pf ..would make it difficult ..if not impossible to use in C band..
but certainly a good idea for a fixed installation .
rgds
VS

 

[Channel Hopper]

The figure of eight shown in illustrations is usually exagerrated in the horizontal plane. For a dish of less than 3 metres, only a vertical correction each 12 hours is required to retain full strength on the satellite.

As Rick has mentioned, two LNBs mounted vertically does the job well for most people, however I had toyed with the idea of using the hinge in the Triax feedarm design to give the correct movement. Now all you need is a pice of string and the services of a punkawalla. (probably not difficult to find in these economic times)

 

[colinp]

I've just purchased an inclined orbit setup from a chap in Bristol that he made himself.I will post picks in the next week or so once it's installed.It was these birds that I bought it for.Regards

 

[Huevos]

The figure 8 movement of an inclined satellite is a tricky enough thing to follow accurately ..
But my question is this ..
Given that the bird 'describes' this movement with presumably a loop above and below the true arc ..
..and that the degree of inclination is described as say 4 degree inclined ....ie ...+ or - 4 degree above and below ...making a total of 8 degees of shift..
Is the figure 8 described .. face on ..in which case it appears to shift laterally as well ..
..or edge on in which case it should appear as though moving only in a vertical dimension ...

The shift is east/west, i.e. lateral shift, but on a 4º inclined satellite it is such a small amount it probably doesn't even equate to one count on your polar axis actuator.

In and out movement is a different thing and is due to eccentricity of orbit. All satellites have this, even ones considered to be holding station perfectly. For example Astra 3B is a brand new satellite considered to be holding station fine, yet over a 24 hour period it wanders in and out between 35,778km and 35,807km. Compare that to Astra 1C and the figures are 35,773km and 35,812km, barely any different. But anyway, for all intents and purposes when you think of a geosynchronous satellite (inclined or not) you can imagine it as being tethered geocentrically and operating at a fixed altitude.

For a dish of less than 3 metres, only a vertical correction each 12 hours is required to retain full strength on the satellite.

I don't agree with this at all. If a bird is inclined 4º, over a 12 hour period there is a shift of 8º (i.e. full south to full north, doing the return trip over the next 12 hours). That is a shift of 1º every 90 minutes and we are talking about movement that is almost linear in relation to time. Even on just a 1 metre dish 1º is a lot to be off target.

 

[Vipersan]

The shift is east/west, i.e. lateral shift, but on a 4º inclined satellite it is such a small amount it probably doesn't even equate to one count on your polar axis actuator.

In and out movement is a different thing and is due to eccentricity of orbit. All satellites have this, even ones considered to be holding station perfectly. For example Astra 3B is a brand new satellite considered to be holding station fine, yet over a 24 hour period it wanders in and out between 35,778km and 35,807km. Compare that to Astra 1C and the figures are 35,773km and 35,812km, barely any different. But anyway, for all intents and purposes when you think of a geosynchronous satellite (inclined or not) you can imagine it as being tethered geocentrically and operating at a fixed altitude.

I don't agree with this at all. If a bird is inclined 4º, over a 12 hour period there is a shift of 8º (i.e. full south to full north, doing the return trip over the next 12 hours). That is a shift of 1º every 90 minutes and we are talking about movement that is almost linear in relation to time. Even on just a 1 metre dish 1º is a lot to be off target.

Hi Huevos ..I'm inclined (pardon the pun)..to agree with you on the 12 hour correction issue ..
For example ...when I went to bed last night around midnight ..
Astra 1D was + 2.8 degrees
..and required a very dramatic re-alignment when I got up around 8:30 >9:AM this morning ..
as it was then roughly -2.8 degrees..

I find that a big dish (1.8pf)..having a tighter beam particularly in ku ..
requires constant adjustment ..at least once an hour to keep max focus/strength ...on 1D
I assume this to be true for 1C also
..maybe an offset dish is more tollerant of vertical movement.
rgds
VS

 

[Channel Hopper]

I don't agree with this at all. If a bird is inclined 4º, over a 12 hour period there is a shift of 8º (i.e. full south to full north, doing the return trip over the next 12 hours). That is a shift of 1º every 90 minutes and we are talking about movement that is almost linear in relation to time. Even on just a 1 metre dish 1º is a lot to be off target.

If you read it within the full context of the post (in keeping with the thread subject, minus women on the side), you will note that I was commenting on foregoing any horizontal adjustment of the dish to counter the apparent East/West movement each 12 hours, the only adjustment required is perpendicular to the geostationary arc.

 

[Vipersan]

..One thing I can say chaps ..
Its a very interesting subject and one I hadn't persued untill recently ..
I'm grateful for all ideas ..hints and tips ..
For my personal setup ..I'd much prefer some form of auto tracking ..
and may well persue this .
rgds all
..gotta go to work now
VS

 

[fergyc]

I've just purchased an inclined orbit setup from a chap in Bristol that he made himself.I will post picks in the next week or so once it's installed.It was these birds that I bought it for.Regards

Very nice can't wait for the pictures

 

[Huevos]

I've spent the day ...trying to track Astra 1C and 1D @2 deg East

What sort of dish size is required (more or less) for those two satellites?

 

[Channel Hopper]

That is a shift of 1º every 90 minutes and we are talking about movement that is almost linear in relation to time.

I'd question this claim. The satellite reaches each maximum of the arc at a constant velocity, and on the earth this would play out as more or less a sinusoidal track. The movement through the arc is however perceived by the ground observer as faster than the outer extremes of the lissajous 'figure of eight' owing to the planar difference. So for the majority of the time (approximately 70% of each twelve hour cycles), the satellite is observed within 30% of the two maximum inclinations.


[tube]Ohp6Okk_tww[/tube]

 

[fergyc]

What sort of dish size is required (more or less) for those two satellites?

80cm is fine

 

[wod]

this is something I want to pick up as it has the rugby league feeds on it now. just need to see how to modify my 1224 to be able to raise/ lower the dish.

vipersan, is it just news on this satelite as I heard championship football feeds are on this too.

 

[Vipersan]

Hi Wod..
Not witnessed any yet ....but there are reports that it is the case ..
Will post if I spot anything ..but its all a bit new to me .
Only been cruising these birds since Sunday.


Ok one for the nature lovers ..
Live lambing feed on 11455H SR6600 3/4Astra 1d
Nature Watch

broadcast in 4:2:2

otherwise only sound..

rgds
VS