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Simple DIY Cheap Theodolite to Check if View to Satellite is Clear.


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Old 06-06-2009, 20:58
SWIZZ?
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Several times, in variety of threads, people have wondered if the building or trees opposite are obstructing the satellite signal. As a caravanner, I often find that the most picturesque sites & pitches involve trees & hills.

To check these obstructions I made a simple theodolite from a school protractor, a plumb-bob & a 1.5mm diameter screwdriver.

Method.

Find your Latitude/longitude from a map, Google Earth or a satnav.

From http://www.al-soft.com get the elevation to your satellite. (It also gives your compass bearing if you aren't just copying your neighbour's).
I have also used http://www.satelliteforcaravans.co.uk but it seems to have a clickjacking problem at the moment ! For caravanning I carry a copy of Dave Sullivans excellent map of Astra 2 elevations across Europe.

Your elevation for Astra 2 should be about 25 to29 degrees in the UK.
Lets say yours was 28 deg. This is 28 deg from the 90 deg in the middle of the scale from 0 to 180 deg. Depending how which way you turn the protractor this will be either marked 118 deg or 62 deg. Drill a small hole at 118 or 62 just big enough to thread your cord attached to the plumb-bob. Tie off the cord with a thumb knot.

Suspend the protractor/plumb-bob, on the 1.5 mm screwdriver, through the hole at the place where all the angle lines converge. With the protractor next to the dish steady the bob & looking along the straight edge, anything in that direction will obscure the view of the satellite.

David
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Old 07-06-2009, 22:39
mk-donald
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Otherwise have a go with the Google Maps based www.dishpointer.com for 28.2E Astra 2A...
and use the draggable "show obstacle (line of sight checker)" element. Helped me know the extension on the house opposite was irrelevant.

MKD
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Old 07-06-2009, 23:46
SWIZZ?
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Otherwise have a go with the Google Maps based www.dishpointer.com for 28.2E Astra 2A...
and use the draggable "show obstacle (line of sight checker)" element. Helped me know the extension on the house opposite was irrelevant.

MKD
There are number of these sites, I quoted
http://www.al-soft.com which site works for me but www.dishpointer.com doesnt because my connection is just below that required "Loading … You need a fast internet connection such as ADSL broadband, Satellite broadband or T1 with a recommended download speed above 1Mbps and javascript enabled." My speed is usually 0.95 Mbps.

How does the program know the height your neighbours extension? & that is in line to the sat.?

I live in rural France & my property is not even on Google maps I find it difficult to see how any such program can tell that my dish can see the Astra 2s between my 2 trees.

Google maps have better coverage in urban areas & you got it to work for your problem extension. However I think the protractor might have been quicker.

David
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Old 08-06-2009, 09:41
grahamlthompson
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There are number of these sites, I quoted
http://www.al-soft.com which site works for me but www.dishpointer.com doesnt because my connection is just below that required "Loading … You need a fast internet connection such as ADSL broadband, Satellite broadband or T1 with a recommended download speed above 1Mbps and javascript enabled." My speed is usually 0.95 Mbps.

How does the program know the height your neighbours extension? & that is in line to the sat.?

I live in rural France & my property is not even on Google maps I find it difficult to see how any such program can tell that my dish can see the Astra 2s between my 2 trees.

Google maps have better coverage in urban areas & you got it to work for your problem extension. However I think the protractor might have been quicker.

David
It does not know the height of an obstruction, you drag a pointer to the object and it tells you how high it has to be to obscure the satellite beam
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Old 08-06-2009, 11:21
SWIZZ?
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It does not know the height of an obstruction, you drag a pointer to the object and it tells you how high it has to be to obscure the satellite beam
So Graham, afterwards you need to estimate both the obstruction height & the height of the dish.

I would use that system if I could not safely get to the dish.
But if you can reach the dish the hanging protracter is so much easier. Try it & see for yourself ! No batteries or $ly subs !

www.dishpointer.com & http://www.al-soft.com seem to work in similar ways but dishpointer needs a fast connection while the al--soft site gave me a download which works offline. It also takes the 2 diameters of your dish & gives the actual dish inclination, for an offset dish.
Great if you are moving around with a caravan & laptop.

David
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Old 08-06-2009, 11:28
grahamlthompson
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So Graham, afterwards you need to estimate both the obstruction height & the height of the dish.

David
Correct. I used a kitchen roll cardboard tube taped at the right angle to a piece of card with a button on a thread as a plumb bob, and pointed the tube in the right direction and simply looked through the tube. Using this I found a place only 6ft high on the side of my house which is near invisible from the front.

http://www.4shared.com/file/93010600...ified=3b65d5bc
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