Tuesday 11 February 2014

Big changes to European reception of UK TV via satellite?


Viewers in parts of continental Europe,
Scandinavia and the Mediterranean
begin to lose further UK free-to-air
channels as a result of the switch to new
satellite Astra 2E.


The BBC satellite move is part of a
second phase of moving TV and
radio services across to a new generation
of three satellites that will provide
the UK and Ireland with TV and radio services
via Sky and Freesat.All of the three new
satellites have a much tighter spotbeam,
specifically designed for the UK and Ireland.
The first phase took place in late 2012,
when Astra 2F went into service and the
first batch of UK free-to-air channels,
including standard definition Channel 5,
were lost across parts of Europe.

Additionally, the reports also indicate
where "sidelobes" around the main spotbeam
are found, and where "nulls" are found.

The best image to illustrate the reception
situation comes from Asia-Pacific satellite
website APSATTV.












This is a cross section of a typical satellite's
footprint on earth.(Don't take too much notice
of the dB numbers here for the following
information.)

The main lobe or the big hump in the middle
- in our case,the UK spotbeam - is over the UK,
Ireland and the low countries.To keep it simple,
the hump is where signal strengths are the best.
To the left (West) reception disappears into
the Atlantic.

To the right (south and east  into continental Europe),
as you go further to the edge of the main lobe,
reception drops off rapidly, and we go into a null.

In the case of Astra 2E, the satellite signal drops
off rapidly over southern France,where dish sizes
for UK TV increase rapidly south of Toulouse.
The same is true over Germany,where a new
East-West divide slices the country in two.

This "null" is, according to reception reports,
over Catalonia, parts of Northern Italy,Austria
and up through parts of the Czech Republic
into Eastern Germany.If you're right under
the null, even the biggest satellite dishes are
unlikely to help. Users in Catalonia have tried and
failed with a 3 metre dish!

Beyond the null are side lobes. You can see in
the picture above the side lobes represented by
a smaller "hump". Places such as Valencia,
Western Poland and Southern Sweden have
reported surprisingly good results on
smaller dish sizes.

Then we go into another null, as we move
further away from the spotbeam.
Southern Spain, for example, is badly hit by
this null. Gibraltar's Panorama website recently
reported that some local satellite installers couldn't
get a signal from sister satellite Astra 2F
(which has a practically identical spotbeam) even
with a 6 metre dish.

As we see in the picture,
a further - but weaker - side lobe comes
into play the further away we get.
This has allowed some in the Canaries to get
some reception with a 3 metre dish - but very
localised and patchy.

Side lobes mean that you can't just assume
that satellite dish sizes need to increase steadily
the further away you are from the spot beam.
In fact, there are distinct 'waves', with dish sizes
increasing near nulls and decreasing near side lobes.


Here's a satellite a footprint map for Astra 2E.
NOTE: dish sizes are designed to be
conservative.
 Some users will have very
professional set-ups with satellite receivers

containing sensitive tuners. Any slight anomalies
or shortcomings in satellite set-ups will have a major
affect in fringe areas.

Some smaller dish sizes might be able to pick
up some,but not all channels on the UK spotbeam.
Early reception reports suggest the "nulls" are
slightly further away from the spotbeam on
 lower frequencies:so some regional variations
of channels may be available, but not others.

In addition,the spotbeam appears to 'wobble' a bit.
As the drop-off around the spotbeam is
so sharp, it means reception can vary

greatly from hour to hour.Some user reports
show that they have lost BBC channels,
before regaining them for a while.
 A larger dish size will normally provide some
reserve when that happens, and also for when
the weather is bad.

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