Archived from groups: alt.tv.tech.hdtv,alt.video.digital-tv (
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Aztech wrote:
> "Bob Miller" <robmx@earthlink.net> wrote in message news:h%RFd.7224
> <
>
>>>So why does the UK operate a MFN big-stick network, with only a few dozen
>>>main sites used for Freeview? We certainly don't have SFN's. I wouldn't
>>>really call a 1083ft transmitter pushing out 1000kW a 'little stick'.
>>
>>He only understands "big stick" when it is in the context of "big power". The
>>UK big stick big power is analog, doesn't count. Must be big stick big power
>>with COFDM. Big stick with little power that works with COFDM simply doesn't
>>compute. They don't want to hear it so they don't.
>
>
> The COFDM transmissions are low power precisely because of the high power
> analogue transmissions, they're paranoid about causing interference, not because
> the analogue transmissions are part of some non-existent SFN. A large
> transmitter pumping out 1MW PAL is accompanied by 8kW DTT, and this somehow
> proves DVB requires too much power... or it will somehow break if too much power
> was used for a "serious" system.
>
> So perversely this thread has told me that COFDM requires much more power to
> operate despite the fact the UK uses really low powers and simultaneously if we
> raised the lamentable ERP's used in the UK to decent levels the system would
> break because it's designed as a SFN (with the slight problem of nothing being
> on a single frequency) and would be inoperable as a serious big stick system.
>
> If anything one would expect things to break at when dealing with levels like
> 8kW, if we had the pleasure of 50-100kW transmissions I could stick a bent
> paperclip in the back of a box with little chance of failure.
>
> This is despite the fact the UK system isn't very elegant, there is no clear
> frequency ranges assigned to digital so muxes are squeezed in the analogue taboo
> (junk) channels at low powers, there are no VHF transmissions, aerials have a
> legacy of 'groupings' so they're only really sensitive to small parts of the UHF
> spectrum and digital transmissions are often outside the suited range resulting
> in poor gain, and because they took the cheap route we have 2K carrier mode with
> resultant guard intervals, 8K silicon was incorporated into all chipsets about
> 18 months later. It may have been the first network in the work but it really
> shows! I don't know how they're managed to shift so many Freeview boxes with
> such a system.
>
> They actually planned a network of high powered SFN's in clear frequency ranges
> (uhf ch30-40), this would of allowed for universal reception and efficient use
> of spectrum instead of the wasteful replication we now have, but they flogged
> the spectrum in '97 to an analogue channel instead!
>
> The planning of the DAB digital radio network is a lot nicer than TV, however in
> this case they use SFN as an excuse for hardly allocating any bandwidth to the
> service. The BBC for instance get 10 radio stations with national coverage into
> 1.5MHz of spectrum, and a commercial operator does the same, by example a single
> national FM station requires 2MHz of fm bandwidth.
>
> If our DVB implementation was done nicely it would knock you off your feet.
>
>
> Az.
>
>
The point is that even the dismal system you have knocks those who
understand it off their feet. BTW just to make the point DAB is COFDM
also and it is DAB using COFDM that the S. Koreans allowed to get their
broadcasters to start broadcasting using 8-VSB. Their broadcasters had
staged a sort of sit down refusing to begin broadcasting with 8-VSB for
YEARS because of how bad it is.
Only with the advent of the 5th gen receiver and DAB COFDM for mobile
were the broadcasters convinced to start using 8-VSB. They have two
channels of 1.25 MHz for DAB in Korea.
US broadcasters would have staged a sit down to but they were implicitly
promised multicast must carry and threatened with the loss of that and
other things if they did not go along with the shakedown and allow
Congress to give LG the 8-VSB monopoly. IF YOU DOUBT THIS just watch
their reaction if Chairman of the FCC Powell sticks to his guns and
DENIES then multicast must carry and their BUDDIES in Congress don't
overturn him.
There will much screaming and gnashing of teeth AND they will demand a
change in the modulation. All the dirty laundry will come out.
Bob Miller
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