Help Required Motorised system fine tuning

[cwsat]

I have a feeling my motorised system is slightly 'out' the more east I go. Turksat is pretty much my stable limit, but it's very weak.

Unfortunately I am completely blocked past 8w so I can't test Hispasat.

My minidish on 28.2e is outperforming my 85cm motorised dish which obviously isn't right. The quality seems down on certain TP's on 19.2e too.

The good news is I have a meter, albeit a ibravebox v9 and my mount and pole are bang on plumb so I am happy it is not that. I am using USALS.

I have read on here it's best to send the dish out to Turksat and tip it backwards / forwards and left and right to see if it is out? If it is, is it simply a case of adjusting the USALS lat and longitude or the arc?

 

[Mickha]

Don't adjust your Latitude, and longitude, as this doesn't appear to be your problem.
It sounds like you're not tracking the satellite arc, correctly.


To find your accurate latitude, and Longitude positions, you can use many apps, but I tend to use dishpointer.com, by typing in your postcode, zooming in on the map, and moving the green icon, to where your dish is located, you can get an accurate Latitude, and Longitude, reading. Remember - (negative), longitude readings = West, positive = East.

 

[ozumo]

Regarding 28.2°E & 19.2°E, Astra satellites have a skew offset of around 7° and Eutelsat birds about half that, so a fixed dish of the same size with correctly skewed LNB will outperform a motorised dish that has zero LNB skew. It's particularly noticeable on transponders where there is another TP with opposite polarity but the same frequency i.e. 11344H & 11344V on 28.2°E.

Pick the satellites you need better reception on and set the LNB skew to suit.

 

[Mickha]

A motorized dish is supposed to move, altering the angle, of the dish, and LNB, to approximate the correct LNB skew, if set up correctly, but I doubt it will ever beat a fixed dish, with a manually skewed LNB.
With an 85cm dish, in the UK, and the power of 28.2E, and 19.2E, you shouldn't need to alter the LNB skew, to peak the signal, providing you set the motor/dish, and LNB up correctly.

 

[cwsat]

I have been out to the dish tonight and firstly, worked out my LNB needed to be moved in the holder, which increased the quality on the weaker TP’s on 1west significantly.

I then moved the dish around to 28.2 and it’s quite clear the dish is tipped too far forward. I put my hand on top of the dish, pulled back gently and gained 10% quality on weaker TP’s.

Out of curiosity I adjusted the dish elevation to perfect the signal levels on 28.2 and then sent it back around to 1west. Significantly weaker.

I have got the dish as good as possible on 1west again.

So it seems it is ‘out’.

On a side note my bravebox v9 never seems to top 85% quality.

 

[Lazarus]

I have been out to the dish tonight and firstly, worked out my LNB needed to be moved in the holder, which increased the quality on the weaker TP’s on 1west significantly.

I then moved the dish around to 28.2 and it’s quite clear the dish is tipped too far forward. I put my hand on top of the dish, pulled back gently and gained 10% quality on weaker TP’s.

Out of curiosity I adjusted the dish elevation to perfect the signal levels on 28.2 and then sent it back around to 1west. Significantly weaker.

I have got the dish as good as possible on 1west again.

So it seems it is ‘out’.

On a side note my bravebox v9 never seems to top 85% quality.

That SQ reading is fine - a great many boxes seem to indicate no higher even though you know that the actual signal is strong and fully coherent.

It's only an indication, not a precision instrument.

 

[ozumo]

I then moved the dish around to 28.2 and it’s quite clear the dish is tipped too far forward. I put my hand on top of the dish, pulled back gently and gained 10% quality on weaker TP’s.

Too much declination. Think of declination as how flat the arc is - reducing it flattens the arc, increasing it does the opposite and tip the dish too far forward as you move away from due south. Send the dish back to 1°W, reduce declination and then lower elevation to peak it. Send the dish back to 28.2°E and see how far off it is.

 

[cwsat]

Going back to basics and working out what is wrong, I am happy the dish is being sent to the right azimuth via USALS.

1west is performing as well as it can.

16e is performing as well as it did when the dish was aligned there statically.

28.2e is tipped too far forward and then continuing east, the issue exacerbates with 42east performing poorly.

The pole is plumb according to the spirit level.

Thinking back to how I set the motor up, I complained the setup guide for my latitude didn’t seem right, the dish was tipped back, I couldn’t get 1west with the elevation bolts undone completely. I then found the link below with others complaining…….

Dark motor supreme owners - elevation or latitude..?

Hi Guys Received a Dark motor yesterday and having problems tracking the ARC - I didn't have too much time to spend on it, before bad lighting stopped play. On the Dark motor bracket, the scale has Latitude on both sides (as opposed to latitude on one side, and elevation on the other (like a...

www.satellites.co.uk

 

[cwsat]

Too much declination. Think of declination as how flat the arc is - reducing it flattens the arc, increasing it does the opposite and tip the dish too far forward as you move away from due south. Send the dish back to 1°W, reduce declination and then lower elevation to peak it. Send the dish back to 28.2°E and see how far off it is.

I need help with the declination. I am trying to work out how to adjust it.

Do I need to reduce the elevation on the motor?

My Gibertini only has an elevation adjustment.

 

[ozumo]

I need help with the declination. I am trying to work out how to adjust it.

Do I need to reduce the elevation on the motor?

My Gibertini only has an elevation adjustment.

When mounted on a motor the elevation bracket on the dish is the declination adjustment. Elevation is adjusted by moving the motor in its bracket.

 

[cwsat]

When mounted on a motor the elevation bracket on the dish is the declination adjustment. Elevation is adjusted by moving the motor in its bracket.

Thanks for confirming.

So send the dish to 1west. Reducing the elevation / declination on the dish will mean increasing elevation on the motor to align 1west?

 

[ozumo]

Thanks for confirming.

So send the dish to 1west. Reducing the elevation / declination on the dish will mean increasing elevation on the motor to align 1west?

Move back to 1°W. Reducing declination is done by raising the dish like you would if you were increasing the elevation of a fixed dish. A little confusing I know. Once declination is reduced the dish will be pointing too high so you then have to reduce the elevation of the motor to compensate. With less declination the dish face will tilt down less as it moves away from due south and hopefully be closer to the ideal arc.

If you still need to pull the top of the dish back to increase 28.2°E signals go back to 1°W and reduce declination and motor elevation again. Or the opposite if you need to push the dish forward. It's mostly trial and error.

 

[cwsat]

Move back to 1°W. Reducing declination is done by raising the dish like you would if you were increasing the elevation of a fixed dish. A little confusing I know. Once declination is reduced the dish will be pointing too high so you then have to reduce the elevation of the motor to compensate. With less declination the dish face will tilt down less as it moves away from due south and hopefully be closer to the ideal arc.

If you still need to pull the top of the dish back to increase 28.2°E signals go back to 1°W and reduce declination and motor elevation again. Or the opposite if you need to push the dish forward. It's mostly trial and error.

Thanks @ozumo I will give this a go.

Would I be better off trying to bring Turksat up in quality and then the rest including 28.2 will follow?

Obviously using the method you have given me.

 

[ozumo]

Would I be better off trying to bring Turksat up in quality and then the rest including 28.2 will follow?

Yes the further away from due south the better as the tracking error will be larger.

 

[cwsat]

Just out of curiosity is there a stronger sat past 42e?

Keep reading about 53e.

 

[ozumo]

Just out of curiosity is there a stronger sat past 42e?

Keep reading about 53e.

52°E Turkmensat is strong though I understand there may be issues with some transponders at the moment.

 

[Terryl]

The could be other reasons that your not tracking right, one is that the pole (or mast) is not rigid enough, and the dish is sagging. two is that the pole or mast mounts are flexing when the dish gets to one side of zero location.

How is the pole/mast mounted (in the ground with or without concrete, or mounted to a wall, on the roof with a tripod mount, or other structure) and what type and how thick is the pole/mast? And how long is it to the bottom of the motor from the last support.

One way to check this is to use two small sperit levels, one mounted just below the motor in an North/South orientation, the other the same location orientated East/West, do this with the dish and motor at Zero,then move the dish/motor and see if it changes.

 

[cwsat]

Went out to the dish this afternoon and the declination was massively out. I think it was 4 journeys too and from 1west to finally get it right.

I have 28.2e performing really well now. Is there such thing as a weak transponder on 28.2? If so, I wouldn’t mind checking it on my meter.

Tomorrow I will have a look past 28.2e and see how Hellas and Turksat perform.

 

[deeptho]

The way to check if you are spot on is to slightly push (at the back) on the dish above and pull below.
If the signal drops and if it also drops when you push at the bottom and pull above then you have reached dish heaven (at least
until you want a bigger dish) .

You can do similar tests at the arc edges, to find out which of the drawings in Michka's first post applies.

In fact, it is better for the dish to point slightly too high (a fraction of a degree) in the center of the arc (1.0W) because that will lead to lower errors
at the arc ends. For an 85cm dish it probably does not matter that much but on a 1.2m dish it helps noticeably.

And once you are satisfied, you need to find some way to mark the current settings (paint?), or to actually measure some angles
on the dish. It is not too difficult to make an inclinometer with same card board and string and obtain a result more accurate (e.g., 0.1 degree)
than with a digital inclinometer. This allows you to realign if for some reason the dish moves.

Also tighten all bolts as much as you can. Otherwise a big storm can undo your work.

 

[a33]

In fact, it is better for the dish to point slightly too high (a fraction of a degree) in the center of the arc (1.0W) because that will lead to lower errors
at the arc ends.

I don't understand what you mean here.
Do you mean to only use the so-called modified dish declination offset angle, but not the modified motor elevation angle (tilting the motor axis forward, towards the equator)?
That would be a funny thing to do, I think. The modified motor angles are normally implemented as a package.

Apart from that, when the fine-tuning is done accurately, he already arrived at the best possible (modified) angles, for center of the arc AND the extremes of the arc.
So, what do you mean, and why would that lead to lower errors?

Greetz,
A33