Jerry Stuckle wrote:
Most likely the company reduced the transmitted power by a factor
of 10 at the time of the switchover, to put the added link margin
in their own pockets.
(transmitting a megawatt of ERP as was regular in the analog days
puts a serious dent in your electricity bill, even when you have
a lot of antenna gain)


Not at all. If anything, they raised their power.

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.


OK, you mean absolute power. Yes, they can lower the ERP - but that
does not necessarily lower the power for the signal. Remember at 1MW
the power was spread over 4.25 Mhz (assuming video only, of course).
Digital requires much less bandwidth, so they don't need as much power
to get the same effective signal. However, digital still requires a
stronger signal than analog, in the bandwidth provided. You need quite
a bit of noise before it becomes visible in analog. Digital, a single
noise pulse can cause the loss of several bits of information. Because
of the compression involved, this is more than one or two pixels.

I think not much of that is correct.
The systems differ a bit between US and elsewhere, but over here the
channel spacing of digital and analog is the same, and the bandwidth
is similar (a bit more for digital if anything).

Also there is no discission of "spreading", we are just discussing
peak envelope ERP.
You could argue that a single digital stream sending 5 programmes
means that 1 programme is transmitted at 1/5 the power, but that is
not what I mean. The total ERP for 1 transmitter has been lowered,
and it transmits multiple programmes to boot.

Digital requires less power because it requires less signal-to-noise
ratio at the receiver.