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Skew angle


Welby1965

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23 minutes ago, Welby1965 said:

Anyone know what the skew angle of an LNB is on a sat dish for a narrow boat??

I don't see how the skew angle alters between a house and a NB, it depends on the latitude of the LNB and hence its position in the 'footprint' of the satellite.

Generally the 'skew' is built in to suit much of the UK, unless you are in the 'extremes' of the UK it should be pretty close as supplied.

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3 minutes ago, Welby1965 said:

In the instructions it says alter the LNB skew to - 14 degs for the Midlands but I'm not sure that is correct given the slope of a NB roof 

The skew is the 'rotational' angle of the LNB within the 'arm', that is not affected by any slope on the roof - are you thinking of 'elevation' which is the angle of the dish to the horizon ( ie tilted up or down)

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7 minutes ago, Alan de Enfield said:

... are you thinking of 'elevation' which is the angle of the dish to the horizon ( ie tilted up or down)

Which (as it sounds) is unaffected by the roof of the boat as is set in relation to the horizon - a spirit level and protractor can be useful for setting this.

 

It only ever needs doing once of course.

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Moor the boat, make sure the dish  has a line of sight to the sat. remembering that you don't need to point the dish straight at the sat. as that is not quite how it works (trees and buildings are a menace) , get it about right using a sat finder - cheap and nasty is fine- and then if you can find a signal strength facility on the telly adjust the dish to the best you can get. This will tell you if the whole caboodle is working properly. We do this half a dozen times a week so it is not as bad as it sounds. Boats wobble so don't use a long pole for the dish - it just exaggerates the movement. If you still have trouble try sitting the dish on a pole on the bank to eliminate other probs. The joints in the co ax cable are vulnerable and we re make ours from time to time.. We have a primitive system and it works well but you must fine tune it from the televisions own signal strength thingy. This works for us all over Europe from Holland down to the Rhone and across to the Rhine and the dish, box, telly, and sat finder are the sort of stuff that most people would not even pull out of a skip.

  • Greenie 1
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Theoretically you'd need to adjust the skew angle of the LNB each time you move the boat as well as pitch and yaw of the dish as the roof of a typical boat slopes with with respect to the horizontal. Also as the water tank is filled and emptied! Similarly, you should be adjusting the pitch angle as you move north and south along the system. In practice, signal strength is much more sensitive to yaw than the other two angles. Back in the days when I used freesat on board, I just set skew angle to the average for roughly the middle of the canal network and that worked perfectly fine. Just adjusted yaw angle with a signal strength meter. Always got a good signal, provided there was nothing, trees, buildings, in line of sight to the satellite.

Jen

Edited by Jen-in-Wellies
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2 minutes ago, Jen-in-Wellies said:

Theoretically you'd need to adjust the skew angle of the LNB each time you move the boat as well as pitch and yaw of the dish as the roof of a typical boat slopes with with respect to the horizontal. Also as the water tank is filled and emptied! Similarly, you should be adjusting the pitch angle as you move north and south along the system. In practice, signal strength is much more sensitive to yaw than the other two angles. Back in the days when I used freesat on board, I just set skew angle to the average for roughly the middle of the canal network and that worked perfectly fine. Just adjusted yaw angle with a signal strength meter. Always got a good signal, provided there was nothing, trees, buildings, in line of sight to the satellite.

Jen

Yes - once set the Skew angle and elevation are set they should not need adjusting, but as you move around (you could be pointing North one day, West the next, etc) then the Azimuth (pointing the dish 28 degrees off South) will need finding every time you move.

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IMO - after years of fiddling around I've found -

Small dishes are a pain as they have no tolerance for the boat moving around

Storing a larger one is a pain, thus I settled for a flat panel 'dish that live in the cabin when we are cruising. Examples can be found on Amazon -

https://www.amazon.co.uk/Satellite-Dish-H30D2-Flat-Antenna/dp/B00319C8W0/ref=sr_1_3?crid=1MMLEFATB22U4&dchild=1&keywords=selfsat&qid=1587461546&sprefix=selfsat%2Caps%2C152&sr=8-3

 

Occasionally you can get returns at a better price.

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