In message , Rob
writes
Ian Jackson wrote:
Here they went from 1 megawatt to about 50 kilowatt (ERP).
And then there are several programmes on one transponder, instead
of one analog programme. This gives significant savings in power.

That's quite s drop in power. In the UK, it seems that the digitals are
being run at 1/5th of what the analogues were. Certainly the main
transmitter for London, Crystal Palace, was 1MW erp, but is now 200kW on
the main six digital muxes. [There are also a couple more running around
10dB less.]

When received with a similar quality setup as was required for longer
distance analog reception, the power is adequate. Of course it does not
allow indoor reception at 50km distance, but in the areas where indoor
reception is advertised there are local transmitters. "the countryside"
still needs a roof-mounted yagi, but they always did.
(I think the spec was a yagi at least 1.5m above the roof and 12m above
the ground)

Of course the 1MW was peak envelope power (at the sync pulses), with a
mean power a lot less than that (for typical content).

That is indeed true.

The UK black level (which is when the highest average power is being
transmitted) is 2.4dB below sync - and peak white (minimum power) is
14dB below sync. Even allowing for the relatively high average power
during the vertical interval, it's obviously the average TV programme
will consume a lot less power than if the transmitter was pumping out
full envelope power all the time. Of course, the 1MW is erp, and as the
transmitting antenna gains can be considerable, the transmitter won't be
putting out 1MW. But again, you've got combiner losses and feeder losses
.......
--
Ian