Re: Next year hdtv law comes into effect

phil-news-nospam@xxxxxxxx wrote: 
On Wed, 27 Jul 2005 16:52:00 -0400 Jeff Rife <wevsr@xxxxxxxx> wrote:

| See, for COFDM, 20 miles is "distant" because beyond that you need vast
| amounts of transmitter power to enable the required S/N to receive HDTV.
| When working with 7MHz channels, SD transmissions, and a maximum of 40
| miles from a transmitter/repeater to *any* home, COFDM does a decent job
| (absent impulse noise).
| | When restricted to US 6MHz channels, HD transmissions, and the need to
| service 70-100 mile distant homes, the 1MW maximum allowed by the FCC for
| digital stations just can't get most (much less all) homes the extra 20dB
| S/N that COFDM would need compared to 8-VSB.
| | One of the great advantages of digital over analog is that it's possible
| to precisely calculate the required S/N for reception. For analog, you
| have to pick a number based on subjective picture quality. The current
| numbers are about 19dB for 8-VSB, about 35-40dB for COFDM (it varies because
| it is unknown what FEC and other settings would be chosen), and about
| 50-60dB for analog NTSC.

So basically you are supporting the idea that 8-VSB could be better than
COFDM in places like West Virginia where a market exists out to 100 miles
or more.  Have you told Bob Miller about this?  Would he even listen?


|> Where did I say there was a chance to change the standard?
| | Mentioning that COFDM might do better under some very limited set of | ircumstances lets the COFDM bozo twist it so that it turns into "COFDM
| is being considered for the US".

How he twists what I say is not my responsibility.


|> | That sort of thing does not work for standards. The biggest reason is
|> | that TV stations have to invest a great deal of money in these things,
|> | and once they have done so, they would not change even if they made the
|> | "wrong" decision.
|> |> It can be a plug-in module of a transmitter. The bit stream portion (e.g.
|> ATSC) would be the same.
| | No, it wouldn't, since the number of bits available would vary a *lot*
| based on settings that are often hard to change.

Presumably the particular parameters chosen for COFDM or 8-VSB in the USA
would be designed to accomodate the ATSC bit rate and the 6 MHz channel
space.  At that point it is a matter of RF path linearity and dynamic
range.  It should be pluggable with a standardized (within the
manufacturer's model line) IF frequency being the output from the modulator
and the input to the transmitter RF section (up convert to transmit
frequency being the next significant stage after any needed common
filtering).


|> | We really don't care, because the US standard has been chosen, and it will
|> | not change. Stop writing things that might give people the wrong idea.
|> |> If you don't care, then don't read my postings.
| | How do we stop the uninformed (but seeking knowledge) from reading your
| uninformed (and merely wanting to cause a ruckus) postings? We can't, so
| we must answer your errors with corrections.

What makes you think I am trying to cause a ruckus?  What errors do you
think I have said that need correcting?  You were the one that jumped to
the _false_ conclusion that nobody ever watches a more distant station if
a closer one carries the same network.  I posted corrections to _your_
errors.


|> But to give you some fodder, yes, I do believe there is a way to make the
|> change happen.
| | There is no way to make the change happen, just like there is no way to
| change cable TV channel frequencies to be "better" for digital cable. Once
| you have a lot of devices sold that use a *standard*, you can't change on
| a whim.

You _can_ change ... you just incur a cost. When the cost is high, it's
generally a good idea _not_ to change. But that does not mean you can't. We _can_ change to COFDM if we want to (and want to incur the cost of
making all the 8-VSB equipment useless). But we most likely do not want
to. But don't use "can't" when that's not correct.


|> Can congress be convinced to reverse all this mess?
| | This, again, is a mistake that uninformed readers must not be confused by.
| There is no "mess" with digital broadcasting in the US. It works, and
| works well, when stations broadcast using full (or close to full) assigned
| power.

I stand by my position that it is a mess.  But that position does not come
from the choice of 8-VSB over COFDM.  My position that it is a mess is
based on the lack of suitable receiving equipment being available, yet
... and ... by the lack of a suitable means to subsidize some kind of
converter program to make an analog cutoff work fairly.

There also seems to be an issue that low-power stations are not testing
digital transmissions.  Someone mentioned an issue with FCC not having
money to buy some software that would allow them to process digital
applications from low power stations.  I think that is nothing more than a
lame excuse.  But I really don't know if any low-power stations are, or
are not, doing digital test/parallel transmissions.  Presumably, a low
power station transmitting with 1/100th the power of a full power station
in analog could cover their same (small) area in digital with 1/100th the
power of that full power station's digital transmission.

You are confusing Low Power TV stations with Full Power TV stations operating at low power. The FCC has allowed full power stations to operate at low power to save money. That is some fraction of the 1700 full power stations in the US. There are also another class of TV stations known as LPTV stations which number some 2700. While finally the FCC has put rules in place for these stations to go digital they have not put in place the software so that those LPTV stations can apply to go digital. For another thing it is far more problematic for a functioning LPTV station to go digital because they have NO must carry on cable rights and 99% are NOT carried on cable so any business they do is truly a broadcast business analog. They have also not been given any transitional other 6 MHz channel to broadcast on so they must HOT SWAP to digital where thier customers have NO or very few receivers.

That is called going out of business overnight.

Bob Miller



| There have been some major setbacks that have little to do with 8-VSB:
| | - most of New York DMA was without digital transmissions for most stations
| after 9/11 since the antennas were on top of the WTC

And the subsequent crunch on suitable antenna space?


| - many stations refused to purchase hardware to support pass through of HD
|  from their networks

That should be a contract issue between the station and their primary
affiliate.


| - multicasting has killed picture quality for quite a few stations

Not that I doubt you, but could you elaborate (so I know more about what
you are saying).


| - stations can't seem to figure out how to send legal PSIP data, and STB
|  manufacturers have managed to build far too many boxes that BSOD when
|  they see those illegal streams

Obviously certain manufacturers have chosen bad programmers and/or bad
operating systems for their development.  Maybe I should do some work on
this myself as I do know software development on Linux and have the PSIP
document from ATSC :-)

So what is the cause of stations not sending valid PSIP (as opposed to
those that just leave it absent)?  Are they, too, using Windows as the
software foundation?  Or are some of the minor flaws in PSIP tripping up
the efforts?


| All in all, 8-VSB is actually a non-issue when talking about the problems
| with the digital transition.

That's fine by me.  I've suspected all along that 8-VSB would be better
for the way I receive OTA TV.  I just don't have the technical documents
to build a case for that.

.

Relevant Pages

  • Re: Next year hdtv law comes into effect
    ... | amounts of transmitter power to enable the required S/N to receive HDTV. ... | When working with 7MHz channels, SD transmissions, and a maximum of 40 ... | miles from a transmitter/repeater to *any* home, COFDM does a decent job ... | digital stations just can't get most homes the extra 20dB ...
    (alt.tv.tech.hdtv)
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    ... One of the differences between analog and digital is that things like ... See, for COFDM, 20 miles is "distant" because beyond that you need vast ... When working with 7MHz channels, SD transmissions, and a maximum of 40 ... digital stations just can't get most homes the extra 20dB ...
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