Today's really stupid question...
Is there a good reason why the satellite that broadcasts TV to the UK
and western Europe is located at 28.x degrees east? Would there be
advantages (eg stronger received signal compared with radiated power)
if the UK's satellite was closer to 0 degrees longitude? Is it because
the area of sky above roughly 0 degrees lat and 0 degrees long is
already occupied by other satellites?
In message <tn79sb$27thh$1@dont-email.me>, NY <me@privacy.invalid> writes
Today's really stupid question...
Is there a good reason why the satellite that broadcasts TV to the UK
and western Europe is located at 28.x degrees east? Would there be
advantages (eg stronger received signal compared with radiated power)
if the UK's satellite was closer to 0 degrees longitude? Is it because
the area of sky above roughly 0 degrees lat and 0 degrees long is
already occupied by other satellites?
Is it so that it can also cover the Indian subcontinent and at least
part of China? (Mumbai is at about 73 degrees east, for instance.)
Today's really stupid question...
Is there a good reason why the satellite that broadcasts TV to the UK and western Europe is located at 28.x degrees east? Would there be advantages
(eg stronger received signal compared with radiated power) if the UK's satellite was closer to 0 degrees longitude? Is it because the area of sky above roughly 0 degrees lat and 0 degrees long is already occupied by other satellites?
Well I know there are satellites close to zero, but it does not make
sense me. If you have a symmetric beam you get a lot of coverage of the Atlantic. I don't think there are a lot of people out there with dishes...
The Europe beam covers a lot a Europe including the UK but is weaker in
the UK.
On 12/12/2022 19:18, David Wade wrote:
Well I know there are satellites close to zero, but it does not make
sense me. If you have a symmetric beam you get a lot of coverage of
the Atlantic. I don't think there are a lot of people out there with
dishes...
The beams are not really symmetrical. They're quite cleverly shaped to
match the required coverage, though the edges are not perfectly well
defined, especially in places where the satellites are nearer the horizon.
The UK beam is relatively narrow and is much weaker over most of Europe.
The Europe beam covers a lot of Europe including the UK but is weaker in
the UK.
The West Africa beam covers a part of Africa starting in the west at
around Guinea eastwards through various countries like Ghana and Nigeria
and finishing just beyond the South East corner of the Democratic
Republic of Congo. The beam is completely separate from the beams
covering the UK and downlink frequencies can be and are reused without causing any problem.
How much is the beam attenuated by striking the UK at an angle of about
28 degrees from vertical in the longitude sense? Is that attenuation
less of an issue than the latitude angle of around 50 degrees (satellite
over equator, UK at about 50 deg N). I suppose the received power can be
made acceptable by making the beam narrower than would normally be
needed, to compensate for it spreading as it strikes the UK at an angle
to perpendicular.
Was a satellite at 28 E chosen simply so a single satellite can use
different antennae to feed a variety of beams to lots of locations in
Europe, western Asia and Africa? Until recently I thought that different parts of Europe used different satellites at different longitudes.
How much is the beam attenuated by striking the UK at an angle of about
28 degrees from vertical in the longitude sense?
On 13/12/2022 01:15, NY wrote:
How much is the beam attenuated by striking the UK at an angle of
about 28 degrees from vertical in the longitude sense?
It isn't. The signal is collected by a dish* or panel that is
effectively at a right angle to the signal direction.
*The small offset dishes have a surface that is actually a section of a larger parabola that has its central axis directed towards the satellite.
Bill
On 13/12/2022 01:15, NY wrote:
How much is the beam attenuated by striking the UK at an angle of
about 28 degrees from vertical in the longitude sense?
It isn't. The signal is collected by a dish* or panel that is
effectively at a right angle to the signal direction.
*The small offset dishes have a surface that is actually a section of a larger parabola that has its central axis directed towards the satellite.
If I've got my geometry (*) correct, the beam touches the earth's
surface at about 80 degrees north/south. But you need to make sure the
signal isn't attenuated by buildings and hills, given that at high
latitudes the dish will be almost parallel with the ground.
In message <tn79sb$27thh$1@dont-email.me>, NY <me@privacy.invalid> writes
Today's really stupid question...
Is there a good reason why the satellite that broadcasts TV to the UK and >>western Europe is located at 28.x degrees east? Would there be advantages >>(eg stronger received signal compared with radiated power) if the UK's >>satellite was closer to 0 degrees longitude? Is it because the area of sky >>above roughly 0 degrees lat and 0 degrees long is already occupied by
other satellites?
Is it so that it can also cover the Indian subcontinent and at least part
of China? (Mumbai is at about 73 degrees east, for instance.)
--
John Hall
"Home is heaven and orgies are vile,
But you *need* an orgy, once in a while."
Ogden Nash (1902-1971)
On 13/12/2022 00:44, Brian Gregory wrote:
The Europe beam covers a lot a Europe including the UK but is weaker in
the UK.
Correction: a little weaker in the UK.
--
Brian Gregory (in England).
On 12/12/2022 19:00, John Hall wrote:
In message <tn79sb$27thh$1@dont-email.me>, NY <me@privacy.invalid> writes >>> Today's really stupid question...
Is there a good reason why the satellite that broadcasts TV to the UK
and western Europe is located at 28.x degrees east? Would there be
advantages (eg stronger received signal compared with radiated power) if >>> the UK's satellite was closer to 0 degrees longitude? Is it because the
area of sky above roughly 0 degrees lat and 0 degrees long is already
occupied by other satellites?
Is it so that it can also cover the Indian subcontinent and at least part
of China? (Mumbai is at about 73 degrees east, for instance.)
Well I know there are satellites close to zero, but it does not make sense me. If you have a symmetric beam you get a lot of coverage of the
Atlantic. I don't think there are a lot of people out there with dishes...
On 14/12/2022 12:50, Brian Gaff wrote:
It depends. a bloke lived in Switzerland when sat transmissions were
analogue. he used to get the feed using a horn aerial made by Revox. He
brought it back over here, and the signals were almost unusable.
Oh wow.
And that was for Astra 2 at 28.2°E in both cases?
It depends. a bloke lived in Switzerland when sat transmissions were analogue. he used to get the feed using a horn aerial made by Revox. He brought it back over here, and the signals were almost unusable.
No, and you also need to realise that we are not just talking about one spacecraft, there are many up there now and with a dish on the ground an angled view of these will make them appear closer together allowing for a narrower capture beam width on the ground. I think its a bit of a trade
off, since you need it far enough above the horizon that ground
obstructions are not a major issue, while realising that the more of the atmosphere you pass through, the more weather will affect the signal. Remember that over most of the trip the signal is in what amounts to a vacuum, and will not lose as much of its strength.
How many satellites are there at 28.x degrees? I thought it was just
two: one at 28.2 which had a beam pattern that was more tightly focussed
on just the UK, and one at 28.5 which also covers a bit of north-west
Europe as well (or maybe the coverage patterns are the opposite way
round). Are you saying that there are actually several at each of the
two longitudes 28.2 and 28.5?
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