How international are Freeview boxes?

On Sat, 27 Sep 2008 12:23:15 +0100, Jim Lesurf wrote:

Well, there should be no noticable difference when the signal is
strong enough. :-)

Is it not also the case that 2k FFT mode does not permit real world
sized SFNs, because usually the transmitters are spaced too far apart
resulting in the timing delay between signals from the two transmitters
being outside of the possible window?

Or in other words, if you want to build a SFN, with sufficiently distant
transmitters, you have to use 8k FFT mode for it to work.

It would appear that OFCOM wishes to have a SFN in the East and in the
South, so if this is the case, these two regions will have to switch to
8k FFT mode at DSO rather than when DSO is complete for all regions.

In article , J G Miller wrote:
On Sat, 27 Sep 2008 12:23:15 +0100, Jim Lesurf wrote:

Well, there should be no noticable difference when the signal is
strong enough. :-)

Is it not also the case that 2k FFT mode does not permit real world
sized SFNs, because usually the transmitters are spaced too far apart
resulting in the timing delay between signals from the two transmitters
being outside of the possible window?

Yes and no. :-)

That isn't simply a question of the FFT mode. It also depends on the guard
interval between symbols, plus other non-code factors like transmitter
spacing and likely coverage areas.

However, yes, the shorter duration symbols of the 2k mode tends to mean you
also want a smaller duration guard interval to avoid too much 'lost time'
in terms of overall data rate.

Or in other words, if you want to build a SFN, with sufficiently distant
transmitters, you have to use 8k FFT mode for it to work.

In principle, you would not 'have to'. But in practice, 8k would be easier
to do without risk of sacrificing something else.

So yes and no. :-)

It would appear that OFCOM wishes to have a SFN in the East and in the
South, so if this is the case, these two regions will have to switch to
8k FFT mode at DSO rather than when DSO is complete for all regions.

Another factor, of course, is to be able to 'clear' a given area for the
chosen frequency. In the present situation and SFN would be hopeless due to
having to fit in the gaps between analogue. After analogue ceases this all
becomes much easier, so SFN is more appropriate. If they do an SFN it will
be interesting to see if it works as planned. Practice has a naughty habit
of not going along with theory. ;-

Slainte,

Jim

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