Jerry Stuckle wrote:
On 3/16/2014 11:42 AM, Ian Jackson wrote:
In message , Jerry Stuckle
writes





HDTV requires a stronger signal than the old NTSC.

It really depends on how good your old analogue NTSC was. For a
noiseless picture, you would need around 43dB CNR, but pictures were
still more-than-watch-able at 25dB, and the picture was often still
lockable at ridiculously low CNRs (when you certainly wouldn't bother
watching it). Digital signals can work at SNRs down to around 15dB for
64QAM and 20dB for 256QAM (although if it's a little below this, and you
will suddenly get nothing).



That has not been our experience. We had a number of customers here in
the DC area who had great pictures on NTSC sets, but got either heavy
pixilation or no picture at all when the switchover occurred. We sent
them to a company which does tv antenna installations (we do a lot of
low voltage, including tv - but not antennas). In every case,
installing a better outdoor antenna solved the problem.

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)

On 3/17/2014 10:45 AM, Rob wrote:
Jerry Stuckle wrote:
On 3/16/2014 11:42 AM, Ian Jackson wrote:
In message , Jerry Stuckle
writes





HDTV requires a stronger signal than the old NTSC.

It really depends on how good your old analogue NTSC was. For a
noiseless picture, you would need around 43dB CNR, but pictures were
still more-than-watch-able at 25dB, and the picture was often still
lockable at ridiculously low CNRs (when you certainly wouldn't bother
watching it). Digital signals can work at SNRs down to around 15dB for
64QAM and 20dB for 256QAM (although if it's a little below this, and you
will suddenly get nothing).



That has not been our experience. We had a number of customers here in
the DC area who had great pictures on NTSC sets, but got either heavy
pixilation or no picture at all when the switchover occurred. We sent
them to a company which does tv antenna installations (we do a lot of
low voltage, including tv - but not antennas). In every case,
installing a better outdoor antenna solved the problem.

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.

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================

Jerry Stuckle wrote:
On 3/17/2014 10:45 AM, Rob wrote:
Jerry Stuckle wrote:
On 3/16/2014 11:42 AM, Ian Jackson wrote:
In message , Jerry Stuckle
writes





HDTV requires a stronger signal than the old NTSC.

It really depends on how good your old analogue NTSC was. For a
noiseless picture, you would need around 43dB CNR, but pictures were
still more-than-watch-able at 25dB, and the picture was often still
lockable at ridiculously low CNRs (when you certainly wouldn't bother
watching it). Digital signals can work at SNRs down to around 15dB for
64QAM and 20dB for 256QAM (although if it's a little below this, and you
will suddenly get nothing).



That has not been our experience. We had a number of customers here in
the DC area who had great pictures on NTSC sets, but got either heavy
pixilation or no picture at all when the switchover occurred. We sent
them to a company which does tv antenna installations (we do a lot of
low voltage, including tv - but not antennas). In every case,
installing a better outdoor antenna solved the problem.

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.

In message , Rob
writes
Jerry Stuckle wrote:
On 3/17/2014 10:45 AM, Rob wrote:
Jerry Stuckle wrote:
On 3/16/2014 11:42 AM, Ian Jackson wrote:
In message , Jerry Stuckle
writes





HDTV requires a stronger signal than the old NTSC.

It really depends on how good your old analogue NTSC was. For a
noiseless picture, you would need around 43dB CNR, but pictures were
still more-than-watch-able at 25dB, and the picture was often still
lockable at ridiculously low CNRs (when you certainly wouldn't bother
watching it). Digital signals can work at SNRs down to around 15dB for
64QAM and 20dB for 256QAM (although if it's a little below this, and you
will suddenly get nothing).



That has not been our experience. We had a number of customers here in
the DC area who had great pictures on NTSC sets, but got either heavy
pixilation or no picture at all when the switchover occurred. We sent
them to a company which does tv antenna installations (we do a lot of
low voltage, including tv - but not antennas). In every case,
installing a better outdoor antenna solved the problem.

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.

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.]
--
Ian

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).

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

Ian Jackson wrote:
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
......

The transmitters feeding the old analog 1MW ERP system were running
40kW output per vision carrier. So antenna gain minus feedline and
combiner losses was 14dB. The feedline was about 300m.
Not RG6, of course :-)

On 3/17/2014 12:09 PM, Rob wrote:
Jerry Stuckle wrote:
On 3/17/2014 10:45 AM, Rob wrote:
Jerry Stuckle wrote:
On 3/16/2014 11:42 AM, Ian Jackson wrote:
In message , Jerry Stuckle
writes





HDTV requires a stronger signal than the old NTSC.

It really depends on how good your old analogue NTSC was. For a
noiseless picture, you would need around 43dB CNR, but pictures were
still more-than-watch-able at 25dB, and the picture was often still
lockable at ridiculously low CNRs (when you certainly wouldn't bother
watching it). Digital signals can work at SNRs down to around 15dB for
64QAM and 20dB for 256QAM (although if it's a little below this, and you
will suddenly get nothing).



That has not been our experience. We had a number of customers here in
the DC area who had great pictures on NTSC sets, but got either heavy
pixilation or no picture at all when the switchover occurred. We sent
them to a company which does tv antenna installations (we do a lot of
low voltage, including tv - but not antennas). In every case,
installing a better outdoor antenna solved the problem.

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.

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================

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.

On 3/17/2014 3:15 PM, Rob wrote:
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.


There are major differences between Europe's PAL and the U.S.'s NTSC.
But the digital signal has much LESS bandwidth than the old analog one.
That was the major impetus over here to switch to digital - to free up
major bandspace in the VHF and UHF spectrums. We now have as many (or,
in some areas, more) stations in a much smaller band than before.

Digital requires less power because the bandwidth is much lower.

--
==================
Remove the "x" from my email address
Jerry Stuckle

==================