Archived from groups: alt.tv.tech.hdtv (More info?)
"Bob Miller" <robmx@earthlink.net> wrote in message
news:y6C1e.43$x4.3@newsread1.news.pas.earthlink.net...
> Robert Peirce wrote:
>> I am very late to this discussion. What is the difference between "8VSB"
>> and "COFDM?" What are the advantages and disadvantages of each?
>>
>> I have a Samsung receiver, presumably 8VSB, connected to a rather large
>> rotating antenna mounted in my attic and I am quite surprised at how good
>> DTV reception is compared to what I get from analog. I am also pleased
>> that digital seems to work 100% or not at all instead of getting fuzzy as
>> analog does. The one problem I have is that certain digital channels seem
>> not always to be working at 100% or even at all. However, when they are
>> up, I get them.
>>
> Better late than never.
>
> Both are digital TV modulations. The way a signal is "modulated" so that
> it can be carried over an analog TV signal. If that is not confusing
> enough I will go on.
>
> COFDM stands for Coded Orthogonal Frequency Division Multiplexing and it
> is not a modulation actually. It is used to refer to QAM modulation that
> has been multiplexed using COFDM. By now you should have a mild headache.
> The core of COFDM, OFDM, was developed at Bell Labs many years ago and was
> updated in Europe with the addition of the "C". Its design direction was
> to solve the main problem of TV analog broadcasting which was multipath
> signal interference. Europe had already had a mis-adventure in their even
> more frenzied response to the Japanese taking over the world of TV when
> they developed and quickly abandoned the HD-MAC system so they were burned
> by HD and retreated to developing a digital system that would allow more
> programming to be delivered via multicasting. Their success in dealing
> with multipath reflections of DTV signals, both dynamic (airplanes,
> traffic dogs and people moving) and static (buildings), created a benefit
> they didn't design for, mobile and portable reception with omni antennas.
>
> 8-VSB is a modulation developed at breakneck speed in fear and loathing of
> all things Japanese in a contest to see you could develop a digital
> replacement for our current NTSC analog TV over the air broadcast system
> that has lost as much as 90% of its customers to cable and satellite if
> you count households who buy or steal cable or satellite. Its design
> parameters included, match the coverage and receive characteristics of
> NTSC and be able to deliver enough bits to carry an HDTV signal compressed
> with MPEG2 compression. It had to be receivable using a 30 ft directional
> antenna. It did not address any of the receive problems of NTSC and it did
> not try to advance the state of the art as to reception. And it didn't.
>
> One major difference with digital reception using COFDM or 8-VSB is that
> if you have interference of a certain amount you will lose the picture
> totally unlike analog reception where snow or lines in the picture do not
> totally kill the reception. So with digital you don't want to have these
> drop outs at all where with analog you can tolerate interference more
> since you may still be able to follow the game or story line.
>
> The big benefit of COFDM is that it does a very good job of handling
> multipath as is demonstrated in this video of mobile reception in the most
> hostile RF environment you can devise, Manhattan. We are using simple 3
> inch and 12 inch omni antennas and the broadcast is coming from a single
> transmitter with only one kW of power.
>
> www.viacel.com/bob.wmv
>
> There are three receivers. The one on the back of the seat is using two
> antennas connected to two tuners that combine the signals of both antennas
> in what is called diversity reception. The other two receivers include a
> USB receiver attached to a laptop and an STB with an internal screen that
> works off the cigarette lighter.
>
> There are six programs being broadcast using MPEG2 though you only see
> three since we do not change the channels in the video. With MPEG4 we
> could deliver up to 16 programs in a year or two. France is going with
> COFDM using MPEG4.
>
> The other advantage of COFDM is that it allows for the use of more than
> one transmitter in a diverse transmitter version of the diverse antenna
> concept. It is called and SFN or Single Frequency Network. It allows for
> each transmitter to be low powered with a much shorter tower and offers
> much better reception than a single stick high powered transmitter while
> using much lower power and being more reliable. If one transmitter fails
> for any reason the network would hardly notice.
>
> We have seen a large number of big stick fires, collapses and terrorist
> hits in just the last few years which have taken OTA broadcasting off the
> air in such places as Moscow, New York and other large populated areas.
> Neither New York or Moscow have totally recovered even after years.
>
> there is more.
>
> Bob Miller
Robert,
Just so you know, bob miller is a notorious usenet crank,
who would stoop so low as to use 9/11 to try to bolster his failed
datacasting/advertising
schemes and his general hatred of our over-the-air HDTV.
"Bob Miller" <robmx@earthlink.net> wrote in message
news:y6C1e.43$x4.3@newsread1.news.pas.earthlink.net...
> Robert Peirce wrote:
>> I am very late to this discussion. What is the difference between "8VSB"
>> and "COFDM?" What are the advantages and disadvantages of each?
>>
>> I have a Samsung receiver, presumably 8VSB, connected to a rather large
>> rotating antenna mounted in my attic and I am quite surprised at how good
>> DTV reception is compared to what I get from analog. I am also pleased
>> that digital seems to work 100% or not at all instead of getting fuzzy as
>> analog does. The one problem I have is that certain digital channels seem
>> not always to be working at 100% or even at all. However, when they are
>> up, I get them.
>>
> Better late than never.
>
> Both are digital TV modulations. The way a signal is "modulated" so that
> it can be carried over an analog TV signal. If that is not confusing
> enough I will go on.
>
> COFDM stands for Coded Orthogonal Frequency Division Multiplexing and it
> is not a modulation actually. It is used to refer to QAM modulation that
> has been multiplexed using COFDM. By now you should have a mild headache.
> The core of COFDM, OFDM, was developed at Bell Labs many years ago and was
> updated in Europe with the addition of the "C". Its design direction was
> to solve the main problem of TV analog broadcasting which was multipath
> signal interference. Europe had already had a mis-adventure in their even
> more frenzied response to the Japanese taking over the world of TV when
> they developed and quickly abandoned the HD-MAC system so they were burned
> by HD and retreated to developing a digital system that would allow more
> programming to be delivered via multicasting. Their success in dealing
> with multipath reflections of DTV signals, both dynamic (airplanes,
> traffic dogs and people moving) and static (buildings), created a benefit
> they didn't design for, mobile and portable reception with omni antennas.
>
> 8-VSB is a modulation developed at breakneck speed in fear and loathing of
> all things Japanese in a contest to see you could develop a digital
> replacement for our current NTSC analog TV over the air broadcast system
> that has lost as much as 90% of its customers to cable and satellite if
> you count households who buy or steal cable or satellite. Its design
> parameters included, match the coverage and receive characteristics of
> NTSC and be able to deliver enough bits to carry an HDTV signal compressed
> with MPEG2 compression. It had to be receivable using a 30 ft directional
> antenna. It did not address any of the receive problems of NTSC and it did
> not try to advance the state of the art as to reception. And it didn't.
>
> One major difference with digital reception using COFDM or 8-VSB is that
> if you have interference of a certain amount you will lose the picture
> totally unlike analog reception where snow or lines in the picture do not
> totally kill the reception. So with digital you don't want to have these
> drop outs at all where with analog you can tolerate interference more
> since you may still be able to follow the game or story line.
>
> The big benefit of COFDM is that it does a very good job of handling
> multipath as is demonstrated in this video of mobile reception in the most
> hostile RF environment you can devise, Manhattan. We are using simple 3
> inch and 12 inch omni antennas and the broadcast is coming from a single
> transmitter with only one kW of power.
>
> www.viacel.com/bob.wmv
>
> There are three receivers. The one on the back of the seat is using two
> antennas connected to two tuners that combine the signals of both antennas
> in what is called diversity reception. The other two receivers include a
> USB receiver attached to a laptop and an STB with an internal screen that
> works off the cigarette lighter.
>
> There are six programs being broadcast using MPEG2 though you only see
> three since we do not change the channels in the video. With MPEG4 we
> could deliver up to 16 programs in a year or two. France is going with
> COFDM using MPEG4.
>
> The other advantage of COFDM is that it allows for the use of more than
> one transmitter in a diverse transmitter version of the diverse antenna
> concept. It is called and SFN or Single Frequency Network. It allows for
> each transmitter to be low powered with a much shorter tower and offers
> much better reception than a single stick high powered transmitter while
> using much lower power and being more reliable. If one transmitter fails
> for any reason the network would hardly notice.
>
> We have seen a large number of big stick fires, collapses and terrorist
> hits in just the last few years which have taken OTA broadcasting off the
> air in such places as Moscow, New York and other large populated areas.
> Neither New York or Moscow have totally recovered even after years.
>
> there is more.
>
> Bob Miller
Robert,
Just so you know, bob miller is a notorious usenet crank,
who would stoop so low as to use 9/11 to try to bolster his failed
datacasting/advertising
schemes and his general hatred of our over-the-air HDTV.
/staff.washington.edu/mrc
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