Getting programming from more than one satellite
The vast majority of satellite television viewers have a fixed
dish antenna, and there's nothing wrong with that if you are satisfied
with the programming available on the satellite that your dish is aimed at.
But what happens when you want a little more?
The cheapest option to get reception from a second satellite
is to fit another lnb to your dish alongside the original one. If the two
satellites you want to receive are reasonably close together, for example
the Astra and Hotbird Clusters at 19ºE and 13ºE in Europe, or the 5ºE and
1ºW satellites in Scandinavia, then this works tolerably well.
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The dual
feed principle.
You may find that you might need a slightly larger dish than
before, because both of the lnbs cannot be sited at the prime focus
of the dish (the most effective place), and there will consequently
be a small loss of signal.
In this case it is a good plan to ensure that the lnb
used to receive the stronger satellite is offset from the dish's centreline,
reserving this position for the weaker satellite.
Notice that to receive a second satellite to the left
of the dish's aim, the lnb has to be offset to the right.
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Because both the Astra-Hotbird and Thor-Sirius orbital positions
are 6º apart, this has opened up a quite large potential market, and some
enterprising manufacturers have produced 'monoblock' lnbs, two lnbs and a
DiSeQc switch in a single housing for just this application.
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A monoblock
lnb
This lnb has an internal DiSeQc switch and consequently
is a direct replacement for your previous lnb.
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So for the cost of a new monoblock lnb or an additional lnb,
mounting hardware and a DiSeQc or manual switch you will have greatly increased
the number of channels available to you for a relatively small outlay.
It is possible to add further lnbs, in combination with a
larger dish, to receive signals from 28ºE, 19ºE and 13ºE for example.
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The
Wavefrontier antenna.
Possibly the ultimate in multiple feed technology.
The specially shaped toroidal sub-reflector means that
you can keep on adding lnbs to receive even more satellites.
But there is a limit to how close together you can
mount the lnbs and it is not a particularly cheap or efficient horizon-to-horizon
solution.
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Alternatively, for maximum signal grabbing power you could
install additional fixed antenna systems for each extra satellite you want
to view.
But by now you are starting to spend serious amounts of
money, and unless near instantaneous switching between satellites or the ability
to watch signals from different satellites simultaneously is important to
you then there is a cheaper and certainly more 'future proof' way of achieving
your goal.
Its is, of course, to motorise your dish.
The pros and cons of motorised dishes
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Motorised
dish features
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Multiple lnb
features
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Satellite
hopping takes a few seconds, swooping from one horizon to the other can seem
very slow if you are impatient.
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Near
instantaneous hopping between satellites
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It's
an expensive solution if you only want to watch 2 or 3 satellites.
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Lower
cost if just 2 or 3 satellites required.
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You
can only watch one satellite at a time.
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With
sophisticated switching, it is possible to watch more than one satellite at a
time, if you have multiple satellite receivers.
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You
can see dozens of satellite positions.
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Number
of satellite positions can be limited by your receiver's software.
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The
lnb will be located at the optimum feed point all the time, maximising your
antenna's efficiency.
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Only
one lnb can be at the optimum feed point (Wavefrontier or Luneberg lens type
antenna excepted, but even then possibly only for a limited arc)
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Adding
additional satellite positions is effectively free.
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You
need to buy a new lnb, cable and perhaps additional switches every time you
want to add another satellite.
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It's
easy to add to or alter the satellites you watch.
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You
need tools/access to dish, good weather etc. to add or alter satellite
positions.
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You
can see satellites positioned very close together in the sky
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Unlikely
that you will be able to see satellites closer than 3º apart, as the lnbs get
in each other's way.
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You
can receive satellites from viewable horizon to horizon.
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Limited
arc of satellites receivable. Even the Wavefrontier dish has limitations
here, tilting the dish can help if you only want to watch half of the sky.
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Minimal
signal losses/reflections water ingress due to breaks in the cable run.
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Potentially
lots of cable joints, increasing the likelihood of signal losses/reflections,
water ingress etc.
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What needs to be done?
The site survey.
Basically this just means picking the best place to install
your dish.
There are a few things to consider.
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The aesthetic point of view, will it look nice, or at
least acceptable to the neighbours, the local planning authority etc.
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The security point of view, how safe will it be from
thieves, vandals etc.
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The safety point of view, will you or your installer
risk life and limb installing or adjusting and maintaining your antenna.
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The mechanical point of view, will your antenna, house,
passers-by, etc. be safe if high winds spring up - as they surely will one day.
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Perhaps most importantly, the technical point of view,
can you actually see the satellites from the chosen location.
We will leave most of these considerations up to you, they
are very dependent on your individual local environment. But we will discuss
the technical side in greater depth.
NEXT PAGE -->>
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