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Default Satellite dish positioning

Has anyone tried using a satellite dish low on the northeast side of a
flat?

Looking at some on-line alignment info, it looks as though for the
Freesat satellite the dish needs to point almost exactly parallel to
surface of the wall, which might attenuate the signal pretty badly
depending on things like possible refraction.

Do any of the satellites further east than the Astra 2 A-B-D also carry
Freesat signals? If so, the dish could be pointed further from the
wall.

The point of this idea is to keep the dish off the roof and out of the
way of roof repairers, aerial installers, and the like.

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Default Satellite dish positioning

Terry Casey writes:

Looking at some on-line alignment info, it looks as though for the
Freesat satellite the dish needs to point almost exactly parallel to
surface of the wall, which might attenuate the signal pretty badly
depending on things like possible refraction.

So long as it is parallel to or angled slightly away from the wall, you
shouldn't have a problem - the beam width is very narrow.


A guesstimate based on eyeballing a Google map suggest that the wall is
in a plane about 40 degrees counterclockwise from due south, i.e. about
140 degrees.
The satellite data says it is at 143 degrees, which would put it 3
degrees behind solid sandstone :-(

However I belatedly thought of looking for other dishes, and can see
one. So maybe......

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Default Satellite dish positioning

David Hansen writes:

Shouldn't do so. Many buildings have satellite dishes in this
position on the walls.


The problem is that the satellite might be out of view, just barely,
_behind_ the side of the wall.

I asked the City if they had any maps showing building orientation, but
seemingly not.

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Default Satellite dish positioning

In article ,
Windmill wrote:
I asked the City if they had any maps showing building orientation, but
seemingly not.


Have you tried one of the sites that superimposes the direction to
satellites on top of Google Maps? E.g. http://www.dishpointer.com

-- Richard
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Default Satellite dish positioning

On Wed, 27 Oct 2010 20:49:26 GMT, Windmill wrote:

The problem is that the satellite might be out of view, just barely,
_behind_ the side of the wall.


At this time of year the sun is roughly in the same position as the
constellation of satellites for Freesat/Sky etc about 0920 GMT (1020
BST)(*). Anywhere that is clearly sunlit at that time should be able
to see the satellites. Dish mounts do let you peek a dish around a
corner.

(*) Fairly sure I've got the time right, if I haven't some one will
no doubt correct me.

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Default Satellite dish positioning

In article o.uk,
Dave Liquorice wrote:

At this time of year the sun is roughly in the same position as the
constellation of satellites for Freesat/Sky etc about 0920 GMT (1020
BST)


This will vary across the country (and of course with the date), so
don't rely on it if it's marginal.

-- Richard
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Default Satellite dish positioning

On Thu, 28 Oct 2010 09:25:47 +0000 (UTC), Richard Tobin wrote:

At this time of year the sun is roughly in the same position as

the
constellation of satellites for Freesat/Sky etc about 0920 GMT

(1020
BST)


This will vary across the country (and of course with the date), so
don't rely on it if it's marginal.


Pay attention to the qualifiers "at this time of year" and "about" in
relation to the time and "clearly" in relation to the illumination.

The bearing will be correct no matter the time of year but I agree
the elevation will change quite a bit between the equinoxes ("at this
time of year") when the sun is more or less in the same place and mid
winter/summer when it will be below (winter) or above (summer) the
position.

I got the time wrong. For here with a longitude of 2.5W it's more
like 1035 BST (I looked at the shadow on our dish...). If I've worked
it out right 1020 would be for a location with a longitude about
1.5E.

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Dave.





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Default Satellite dish positioning

In article , spam-no-
lid says...

Terry Casey writes:

Looking at some on-line alignment info, it looks as though for the
Freesat satellite the dish needs to point almost exactly parallel to
surface of the wall, which might attenuate the signal pretty badly
depending on things like possible refraction.

So long as it is parallel to or angled slightly away from the wall, you
shouldn't have a problem - the beam width is very narrow.


A guesstimate based on eyeballing a Google map suggest that the wall is
in a plane about 40 degrees counterclockwise from due south, i.e. about
140 degrees.
The satellite data says it is at 143 degrees, which would put it 3
degrees behind solid sandstone :-(


The satellite data will be WRT true north but, if the map data
originates from the Ordnance Survey, it will be WRT grid north, so you
may not be comparing like with like ...

.... and you did say 'about 40 degrees'! How accurate is 'about'? After
all, a 3 degree discrepancy could mean the difference between success
and disaster ...!

You may find this useful:

http://www.macfh.co.uk/JavaJive/Audi...SatelliteCalcu
lator.php

or

http://tinyurl.com/3afzpuw

This uses Google maps but, if you enter your OS grid reference or
PostCode, you also have the option of using OS maps.

If the position is not quite accurate, you can drag the dish location
around the map. At maximum zoom, the OS shows the outlines of buildings,
which might be particularly useful to you ...!

--

Terry
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Default Satellite dish positioning

In article o.uk,
Dave Liquorice wrote:

The bearing will be correct no matter the time of year


That's not true, unless you read the time from a sundial rather than a
mechanical clock. The eccentricity of the earth's orbit and the fact
that the sun does not stay exactly within the plane of the equator mean
that sun time varies from human time by up to 16 minutes, which
corresponds to an error in the bearing of up to 4 degrees.

See http://www.sundials.co.uk/equation.htm

-- Richard
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Default Satellite dish positioning

(Richard Tobin) writes:

Have you tried one of the sites that superimposes the direction to
satellites on top of Google Maps? E.g.
http://www.dishpointer.com

I'll try that. The map I was using showed a line but not its compass
heading, which by inaccurate eyeball was approx. 140 degrees.

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Default Satellite dish positioning

(Richard Tobin) writes:

Have you tried one of the sites that superimposes the direction to
satellites on top of Google Maps? E.g.
http://www.dishpointer.com

Tried that one; it's better than the one I used before. It shows that
the line-of-sight to the satellite is about 0.1 degree more than the
angle of the rear, NE side, of the building (just guessing, it barely
converges with the rear of the building over a distance of about six
stairs spacing; maybe 500 feet).

Amazing coincidence.

So if the dish is fixed a few feet from the wall it _should_ work.

Thanks for the pointer.
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Default Satellite dish positioning

"Dave Liquorice" writes:

On Wed, 27 Oct 2010 20:49:26 GMT, Windmill wrote:


The problem is that the satellite might be out of view, just barely,
_behind_ the side of the wall.


At this time of year the sun is roughly in the same position as the
constellation of satellites for Freesat/Sky etc about 0920 GMT (1020
BST)(*). Anywhere that is clearly sunlit at that time should be able
to see the satellites. Dish mounts do let you peek a dish around a
corner.


It's a very very close thing, but there is one (only one) other dish
along the whole length of the street i.e. in about 100 rear-facing
flats.
So either possible, or the dish owner has been disappointed.

Might have to build a contraption to space the dish away from the wall.


--
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Default Satellite dish positioning

(Richard Tobin) writes:

Have you tried one of the sites that superimposes the direction to
satellites on top of Google Maps? E.g.
http://www.dishpointer.com

Just had another look, to reconfirm that a dish will probably work.

Amusingly it tells me that my nearest satellite installer is in
Mississauga, Canada !

--
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Default Satellite dish positioning

In article ,
Sam Wilson wrote:

This is probably a bad idea since I know almost nothing about how radio
waves propagate at sat-TV frequencies, but is there any chance of
getting a reflection of something at the other side or at the end of the
block?


I don't think that works. For expert advice try uk.tech.digital-tv.

-- Richard
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Sam Wilson writes:

This is probably a bad idea since I know almost nothing about how radio
waves propagate at sat-TV frequencies,


Pretty much straight line, I think. Otherwise the airport surveillance
radars which show ATC/S where on the taxiways planes are on a foggy day
or after dark wouldn't be much use.
(I think that's called X band , or some such, running at frequencies
vaguely similar to satellite Ku band.)

but is there any chance of
getting a reflection of something at the other side or at the end of the
block?


Quite probably, but AIUI the direct signal is already very weak, having
travelled 22,400 miles.
I'm sure one could use a reflection if one used a 30 foot dish, say,
but......

I also assume you're not on the ground floor since you would
already have thought about mounting the dish on the ground away from the
wall, right?


One floor up.

I'm pondering where best to put the dish so the protruding [ shaped
attachment to the neighbouring drainpipe doesn't get in the way. But I
don't know the elevation above our horizontal of synchronous satellites
at our latitude.
About 30 degrees, I'm guessing. Obviously I will learn this along the
way!

--
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Default Satellite dish positioning

In message , Windmill
writes
Sam Wilson writes:

This is probably a bad idea since I know almost nothing about how radio
waves propagate at sat-TV frequencies,


Pretty much straight line, I think. Otherwise the airport surveillance
radars which show ATC/S where on the taxiways planes are on a foggy day
or after dark wouldn't be much use.
(I think that's called X band , or some such, running at frequencies
vaguely similar to satellite Ku band.)

but is there any chance of
getting a reflection of something at the other side or at the end of the
block?


Quite probably, but AIUI the direct signal is already very weak, having
travelled 22,400 miles.
I'm sure one could use a reflection if one used a 30 foot dish, say,
but......

I also assume you're not on the ground floor since you would
already have thought about mounting the dish on the ground away from the
wall, right?


One floor up.

I'm pondering where best to put the dish so the protruding [ shaped
attachment to the neighbouring drainpipe doesn't get in the way. But I
don't know the elevation above our horizontal of synchronous satellites
at our latitude.
About 30 degrees, I'm guessing. Obviously I will learn this along the
way!

In the UK, the Astra 2 A-B-D - Eurobird 1 bunch (at appx 28.2) are at an
elevation of around 25 degrees, depending on your latitude. It's
surprising how low that is!

BTW, I'm also in the process of getting a satellite system going, and I
find that this is definitely one of the more useful sites for programme
and channel information:
http://en.kingofsat.net/freqs.php?&p...ordre=freq&fil
tre=Clear
--
Ian
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Default Satellite dish positioning

tony sayer writes:

[......] but is there any chance of
getting a reflection of something at the other side or at the end of the
block?

Just wouldn't be strong enough to do that, let along at being just the
right angle etc!...


ISTR that reflection also rotates the plane of polarisation by 90 deg.
Which would confuse these LNB things, because apparently different
channels are transmitted with different polarisations.

I read that this is the reason why you need LNBs with two or more
outputs if you want to have two or more TVs able to receive different
channels at the same time - a single LNB output can be switched by a
single sat receiver to receive differently polarised signals, but it
can't be set for both vertical and horizontal polarisation at the same
time.

Or that's my understanding.

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Default Satellite dish positioning

On Fri, 29 Oct 2010 19:30:58 GMT, Windmill wrote:

But I don't know the elevation above our horizontal of synchronous
satellites at our latitude. About 30 degrees, I'm guessing.


Close enough but remember if you are talking about a Sky "mini dish"
they are offset dishes. This means that the face of the dish is more
vertical than one would expect.

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Dave.



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Default Satellite dish positioning

On Mon, 01 Nov 2010 15:11:54 +0000 (GMT) someone who may be "Dave
Liquorice" wrote this:-

Close enough but remember if you are talking about a Sky "mini dish"
they are offset dishes. This means that the face of the dish is more
vertical than one would expect.


In southern Scotland the dish of offset dishes is usually pretty
much horizontal. In the north the dish can appear to point
downwards.


--
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Default Satellite dish positioning

In message , David Hansen
writes
On Mon, 01 Nov 2010 15:11:54 +0000 (GMT) someone who may be "Dave
Liquorice" wrote this:-

Close enough but remember if you are talking about a Sky "mini dish"
they are offset dishes. This means that the face of the dish is more
vertical than one would expect.


In southern Scotland the dish of offset dishes is usually pretty
much horizontal.


I think you meant 'vertical'.

In the north the dish can appear to point
downwards.


From Gretna Green to Lerwick (which is a long way east), the difference
is about 3 degrees (for an elevation of around 17 to 21 degrees).

From Gretna Green to Kirkwall, it's a bit less.

http://www.dishpointer.com/
--
Ian
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Ian Jackson writes:

Don't forget that the polarization of the signals is 'skewed', so they
don't arrive exactly horizontal and vertical. The LNB will need to
mounted so that it is also skewed (rotated in its mounting clamp). In
the case of the 28 degree east satellites, the skew angle is around 13
degrees clockwise, looking towards the dish.


Useful info; thanks.

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