AVS Forum banner

Status
Not open for further replies.
1 - 14 of 14 Posts

·
Banned
Joined
·
35 Posts
Discussion Starter #1


Geof, the moderator on Denver HDTV Tower topic, said this post is off topic there so I should start a new one.


This is very confusing and is giving me a headache. I read the article twice now and i will read it again but bear with me. (Article http://www.digitaltelevision.com/future11.shtml)


The article says that translators (some kind of station that rebroadcast NTSC TV stations) were taken away from NTSC stations to be used as DTV stations. The article says that instead of using one big stick antenna in a place like Denver you could use a ring of smaller antennas at much lower power (I Like that) and you are saying with this 8-VSB we could use translator stations. How many of these translator stations are there and would you have to take a lot of them away from what they are being used for now? I assume being used by other NTSC stations. (regular TV)


The article was saying you could use the same channel somehow as "on-Channel" repeating. Let me copy part, "It may also help the FCC deal with the problems of replicating service for the thousands of NTSC translators and LPTV stations that are being disenfranchised by the allocation of two channels to high power broadcasters during the simulcast period."


It sounds like the other way you could do this all with only one channel and would't have to use these translators.


Either way if you can get rid of the big broadcast antennas and all that microwaves that are burning people that would be good.


This paragraph caught my eye. Can translators do this. You say they were tested sucessfully in Utah. "Let's assume that we place five 300-foot towers around our stadium. It is highly likely that those inside the stadium will see more than one signal. If these signals are properly synchronized they add together to increase the signal level at any given reception site. Outside the stadium viewers at the fringes are likely to see a strong signal from the closest tower. If they are occluded from the cells around the stadium by geographic features (e.g. mountains and valleys), it is possible to add low power on-frequency repeaters to serve the population pockets around a market. Here, syncronization is less of a concern. It may be possible to simply receive the signal from the large cell transmitters and re-broadcast it out of sync with the main cells; in this case the power level from the local transmitter will be significantly higher than the distant signal, allowing a receiver to easily differentiate the local signal."


Is there anything else I should read on translators?
 

·
Registered
Joined
·
10 Posts
Rotary,


I could not find the article you referred to in your question, so I ended up being a little confused. Maybe some definitions will help us out.


Excluding satellite delivery, there are three possible methods of over the air (OTA) delivery of ATSC signals to homes that are not able to receive the primary station directly: Single Frequency Networks (SFN), On Channel Boosters (repeaters), and Translators.


SFNs are very rare in this country for TV delivery. They are being used in Europe, increasingly with digital signals. SFNs are groups of relatively low power transmitters all fed with signals locked to a reference time. These transmitters then send the signals out over the air, all transmitting on the same channel.


On channel boosters receive their inputs directly from the primary station. The signal is amplified and sent to a transmit antenna. Since the transmitted channel is the same as the received channel, the transmit and receive antennas must be "isolated" from each other. If you have ever held a microphone close to the amplified speaker it is connected to, you have an idea of what happens if there is not enough isolation between the receive and transmit sides of an on channel booster. On channel boosters are not widely used in this country because of this. However, ATSC signals require less isolation and therefore on channel boosters may become more widespread.


Translators receive the primary station, or any other TV signal source, change the frequency, and then amplify and transmit the signal on the new frequency. This nearly eliminates the need for isolation between the receive and transmit sides of the device. Translators have proven to be a very effective way of extending the reach of primary stations in this country, thousands are in use.


IMO, translators, along with some on channel boosters, will be the devices used to fill in the inevitable holes in ATSC coverage. Much of the infrastructure is already in place. Building SFNs for TV delivery would be very expensive and technically challenging to say the least.


Paul
 

·
Banned
Joined
·
35 Posts
Discussion Starter #3
Quote:
Originally posted by PRB:
Rotary,


I could not find the article you referred to in your question, so I ended up being a little confused. Maybe some definitions will help us out.


Excluding satellite delivery, there are three possible methods of over the air (OTA) delivery of ATSC signals to homes that are not able to receive the primary station directly: Single Frequency Networks (SFN), On Channel Boosters (repeaters), and Translators.


SFNs are very rare in this country for TV delivery. They are being used in Europe, increasingly with digital signals. SFNs are groups of relatively low power transmitters all fed with signals locked to a reference time. These transmitters then send the signals out over the air, all transmitting on the same channel.


On channel boosters receive their inputs directly from the primary station. The signal is amplified and sent to a transmit antenna. Since the transmitted channel is the same as the received channel, the transmit and receive antennas must be "isolated" from each other. If you have ever held a microphone close to the amplified speaker it is connected to, you have an idea of what happens if there is not enough isolation between the receive and transmit sides of an on channel booster. On channel boosters are not widely used in this country because of this. However, ATSC signals require less isolation and therefore on channel boosters may become more widespread.


Translators receive the primary station, or any other TV signal source, change the frequency, and then amplify and transmit the signal on the new frequency. This nearly eliminates the need for isolation between the receive and transmit sides of the device. Translators have proven to be a very effective way of extending the reach of primary stations in this country, thousands are in use.


IMO, translators, along with some on channel boosters, will be the devices used to fill in the inevitable holes in ATSC coverage. Much of the infrastructure is already in place. Building SFNs for TV delivery would be very expensive and technically challenging to say the least.


Paul
Sorry about that. The URL had a ) at the end that should not have been there.

http://www.digitaltelevision.com/future11.shtml


Basically it says that on-channel repeaters can see each other if they use this COFDM. In fact I just got an email that says the entire country of England is nothing but on channel repeaters and low powered transmitters. It also talks about a company, Pace, that is trying to make boxes like the Australian one I presume for as little as 25 Pounds. That would be like $35.00. Is this possible? The email says it is unlikely but they are endeavoring to do it.


This just gets more confusing. People on this forum seem to think (some of them anyway) that what we are using in the US, is it ATSC or 8-VSB or both, is the best. I can't get answers to almost anything here however. Your post is the exception.


They say I am off topic if I ask if the tower problem in Denver could be solved with this idea in the article you now should be able to get. I ask about the cheap box the Aussies have and they say it is irrelevant even though it does HDTV just like we are doing here. We are stuck with what we are using I am told. Why? If it is not the best or if it requires much more expensive boxes to receive it the FCC should be doing its best to get it changed before it is too late.


The Aussies have a box that cost $346.00 installed that does HDTV. The Brits are trying to get the cost of a box down to $35.00. The best we have is $500.00. How long have we been trying? Is there any hope the way we are going? I have a list of countries now that are not compatible with our system. Wouldn't our system have to be not just as good but better than this other to justify being different than everybody else?


Maybe that is why our boxes cost so much. They have economies of scale that we don't and they haven't even been at it as long as we have. Australia just started three months ago and they have sold 2500 boxes that don't even do HDTV yet. That would be the same as 35,000 here.


Bob U says that is all we have in use in the US after four years (35,000). Is that accurate? I can't seem to get any figures. Except in England that is they have one and a half million digital boxes in use.


I am waiting on information about Germany. this sounds spectacular. They claim that by the end of the year they will have a mobile system working over a part of the country where you can get perfect reception of digital TV with these SFNs and on channel repeaters.


Could we do that here?

 

·
Registered
Joined
·
5,658 Posts
Quote:
This just gets more confusing. People on this forum seem to think (some of them anyway) that what we are using in the US, is it ATSC or 8-VSB or both, is the best. I can't get answers to almost anything here however. Your post is the exception.
ATSC = Advanced Television Systems Committee. They are the responsible organization and governing body for Digital Television (DTV). For more information on this visit http://www.atsc.org/


The ATSC spec (A53) that governs DTV specifies 8VSB as the modulation. 8VSB modulation was chosen by the ATSC and also by the Canadians and S. Koreans. The rest of the world is pretty much using a different modulation - COFDM (or a variant). Each of these modulation types has strengths and weaknesses that make each suitable for different situations. If, as you say, England is made up of "nothing but on channel repeaters and low powered transmitters" then this is ideally suited for COFDM. The US, as you know, has never had this type of TV distribution. We have a different approach wherein the local stations have a big-ass transmitter that broadcasts as far as it can and to as many people as it can. This is not a strength of COFDM - 8VSB is better suited to this brute force approach.


The bottom line is that the US uses 8VSB whereas England, Australia, and many other counties do not. You cannot import any of those STB’s into the States and expect them to receive anything, let alone TV.


There are not a lot of Australians participating in this forum. As such most of us on this forum aren’t familiar with the Australian situation. I do know some fundamental facts such as when Australian DTV went online (January) and that so far sales are very slow. Asides from that I could not begin to tell you why their STB’s are cheaper (maybe the are subsidized?).


Quote:
They say I am off topic if I ask if the tower problem in Denver could be solved with this idea in the article you now should be able to get.
Again, COFDM is not being used in this country. Whether this approach would help the Denver situation is irrelevant because even if it could it cannot be used. The Denver folks have no H/DTV towers (except for Fox which does not broadcast HDTV) and that is what that thread is about. It is not about discussing theoretical solutions that have absolutely no chance of being implemented.


Finally, Bob U has an "axe to grind" with 8VSB. He loathes Zenith (the inventor of 8VSB) and well, you decide from there but he is clearly very biased. For sales figures of STB’s I would suggest you rely on the CE sales figures, not what Bob says.



------------------

Geof


[This message has been edited by Geof (edited 04-09-2001).]
 

·
Registered
Joined
·
632 Posts
Quote:
Originally posted by Rotary:
The Aussies have a box that cost $346.00 installed that does HDTV.
Where did you get that information? The quote from the Aussie broadcaster in another thread says it is a DTV (or SDTV) box, NOT a HDTV box.

 

·
Banned
Joined
·
35 Posts
Discussion Starter #6
Quote:
Originally posted by ADent:
Where did you get that information? The quote from the Aussie broadcaster in another thread says it is a DTV (or SDTV) box, NOT a HDTV box.
Here is the URL. Let me know what you think. If it works like they say it does this is what I want. You can hook it up to your regular TV. It would have to be PAL. But I just got the info that this will in fact do 576p which is something they are broadcasting over there.


I understand 1080i is the best. 720p is very good so 576p would be close to HD. I am told that in Australia they are doing triplecast. Analog PAL similar or a little better than our analog and two digital signals, 576p and 1080i.


Does that mean that you could get 576p on their regular TV with this box. I don't know. Somebody from OZ out there?

http://goanna.cs.rmit.edu.au/~pmcd/HD-STB.pdf

 

·
Registered
Joined
·
4,038 Posts
576p is regular PAL in progressive mode.

It is not HDTV, just like 480p is not HDTV.

AS far as HDTV in Australia, they have adopted complete

ATSC spec except they picked COFDM instead of 8VSB for OTA.

There is no triplecast and so far from what I heard there

wasn't any shows broadcast in true HD.

BTW since DTV started there in January a lot of people

complained that digital signal was interfering with

adjacent analog channels.
 

·
Registered
Joined
·
110 Posts
Quote:
Originally posted by Rotary:
I understand 1080i is the best. 720p is very good so 576p would be close to HD. I am told that in Australia they are doing triplecast. Analog PAL similar or a little better than our analog and two digital signals, 576p and 1080i.


Does that mean that you could get 576p on their regular TV with this box. I don't know. Somebody from OZ out there?
First a bit of background:

The main difference between PAL (Phase Alternate Line) and it's variant, SECAM (Sequential Couleur avec Memoire) and our NTSC is that they are synched to Europe's 50Hz power grid, versus the North American 60Hz. Therefore, PAL/SECAM use 50 interlaced fields per second, yielding 25 frames per second, vs. 60 fields or 30 FPS (actually, 29.97 - but that's another story). PAL uses 625 lines of vertical resolution (575 actual picture lines) while NTSC uses 525 (484 actual). Horizontal resolutions are 425 pixels for PAL, 465 for SECAM, and 427 for NTSC. All three systems use the same method for luminance ("black and white"), but difference methods for encoding color information.


So, the Australian 576p digital transmission is actually presented to the television as a 575i PAL signal. It is not a progressive signal.


There are several reasons why the Australian STB is cheaper than those in the US:

(1) They don't include DirectTV or DISH tuners, so no royalties included in the price;

(2) They don't include CATV tuners (QAM or 16-VSB), so the chipsets are cheaper;

(3) They don't output 720p or 1080i component video signals for HDTV, so those chipsets aren't needed, dropping the cost even more.


[I've since seen that the boxes do have 1080i component, so I stand corrected. Some have suggested that the boxes have been underwritten by the Aus. government, but I can't be sure. It's possible that they are being sold below manufacturing cost to jumpstart the market, though.]


But the main reason US boxes are so expensive right now is simple economics: supply and demand. Demand is very high right now, and supplies are very low. There is a healthy supply of RCA DTC-100 boxes right now, but most people want newer generation boxes with 2nd generation tuners. Stock levels of the Mitsubishi, Sony, Samsung, etc. boxes are very low or on allocation until manufacturing runs pick up.


A couple of manufacturers are supposed to introduce STB's similar to the Australian ones to the US market later this year - OTA only, composite and S-Video NTSC outputs only - no 480P/720P/1080I. They are the "$100" boxes the FCC talks about. The initial pricing will be less than $300, but will eventually drop over time to $50 or so. Plus DTV tuners will be incorporated into low-end TVs per FCC mandate.





[This message has been edited by jonlgauthier (edited 04-11-2001).]
 

·
Banned
Joined
·
35 Posts
Discussion Starter #9
Quote:
Originally posted by CKNA:
576p is regular PAL in progressive mode.

It is not HDTV, just like 480p is not HDTV.

AS far as HDTV in Australia, they have adopted complete

ATSC spec except they picked COFDM instead of 8VSB for OTA.

There is no triplecast and so far from what I heard there

wasn't any shows broadcast in true HD.

BTW since DTV started there in January a lot of people

complained that digital signal was interfering with

adjacent analog channels.
They will start broadcasting HDTV 1080i in June the same time this new box becomes available.


I like DVD quality and I know what that looks like and it is 480i or it could be 480p if you line double it right? I saw 480p on a rear projection system (8 ft. wide or so) and they said it was doubled DVD. That was awesome (Perfect Storm) so I would think that 576p on a much smaller screen would be good. I saw 720p demo on a computer monitor (Panasonic), stunning. I would like to see 1080i on a large screen.


Here is an email form OZ


"Clearer (no ghosts, RF or analogue type interference) and 16:9 wide

pictures.

DD 5.1 on some SD and all HD transmissions. STB has S/PDIF digital out for

DD amps.


This is the box to get if you're remotely interested in DTV. It's more

future proof than the Thomson or TEAC, or the current gen 1 SD units. It has

a multitude of vision outputs including 15 pin VGA for connection to a

Computer Monitor (Big 21" should look good displaying native 1080i,

progressively), or Data Projector, right down to old 4:3 PAL composite.


It's audio is on the button for me being digital output and as far as I know

they aren't going to get better than DD 5.1 any time soon, so it's perfect

in my particular DD only system.


It's the same price as the Thomson and TEAC SD boxes on the market now, and

it offers so much more.


Ivan


What is DD 5.1 and do we have that in our system?

 

·
Registered
Joined
·
5,658 Posts
To all who may reply...


ROTARY = Bob Utne


All he is trying to do is goat us.


------------------

Geof
 

·
Banned
Joined
·
35 Posts
Discussion Starter #11
Quote:
Originally posted by jonlgauthier:


So, the Australian 576p digital transmission is actually presented to the television as a 575i PAL signal. It is not a progressive signal.


There are several reasons why the Australian STB is cheaper than those in the US:

(1) They don't include DirectTV or DISH tuners, so no royalties included in the price;

(2) They don't include CATV tuners (QAM or 16-VSB), so the chipsets are cheaper;

(3) They don't output 720p or 1080i component video signals for HDTV, so those chipsets aren't needed, dropping the cost even more.


[I've since seen that the boxes do have 1080i component, so I stand corrected. Some have suggested that the boxes have been underwritten by the Aus. government, but I can't be sure. It's possible that they are being sold below manufacturing cost to jumpstart the market, though.]


But the main reason US boxes are so expensive right now is simple economics: supply and demand. Demand is very high right now, and supplies are very low. There is a healthy supply of RCA DTC-100 boxes right now, but most people want newer generation boxes with 2nd generation tuners. Stock levels of the Mitsubishi, Sony, Samsung, etc. boxes are very low or on allocation until manufacturing runs pick up.


A couple of manufacturers are supposed to introduce STB's similar to the Australian ones to the US market later this year - OTA only, composite and S-Video NTSC outputs only - no 480P/720P/1080I. They are the "$100" boxes the FCC talks about. The initial pricing will be less than $300, but will eventually drop over time to $50 or so. Plus DTV tuners will be incorporated into low-end TVs per FCC mandate.


[This message has been edited by jonlgauthier (edited 04-11-2001).]
Ok so you have 1080i and 720p but the 576p becomes 576i for a normal TV. I wonder if they could view it on a computer monitor and see the 576p?


COFDM has a QAM modulation so wouldn't it need a CATV tuner whatever that is. The description of COFDM says that it is Coded Orthongonal Frequency Division Multiplexing and the multiplexing means that it divides the one channel into 7000 channels and that in each one they have QAM. Which is similar to AM like AM radio?


But it doesn't have a satellite receiver like dish. That would make it cheaper.


Don't understand the bit about supply and demand. In England they have sold millions as part of a subscription service and the price is between $200 and $300 and they have been doing it for less time than we have. I don't see any advertising for them either. A very quiet demand. A very small supply.

 

·
Registered
Joined
·
110 Posts
CATV was originally "Community Access Television", now generally taken to mean CAble TV. The most popular modulation schemes in the analog world are QAM and 16-VSB. COFDM is a variation on Quadrature Amplitude Modulation, but not exactly. A COFDM-only tuner can't receive a cable QAM signal.


QAM is not quite like AM. Regular AM modulation is not phase-shifted. Quadrature means shifted by 90 degrees, or one quarter of a circle (360 degrees). That way you can encode 4 bits per baud (or signal transition) - pack more data into the same bandwidth.


You have the right ideal about the 7000 channels in COFDM. It is real similar in concept to ADSL in the Internet world. Chop up your available bandwidth into little chunks so that in the presence of noise, you lose some channels, but data still gets through on the others. ADSL is usually static - you test the phone line and use the max. number of channels you can. Rate-Adaptive (RADSL) is perhaps a better analogy to COFDM.


As far as the economics lesson - classical supply and demand theory says that when supplies are limited (i.e, manufacturers can supply enough boxes to meet customer demand), prices rise. As an exercise, call any Mitsubishi dealer and see how long the wait is for Mitsu's SR-HD500 or 400... "Millions of receivers" in England is a huge supply! A recent article stated that even though the government is subsidizing the cost of the receivers to "buy" votes (one per household), there are still many people who won't purchase them!


If you listen to some naysayers on this forum, STB's are stacked in warehouses because no one wants to buy them. Nothing could be further from the truth!

Quote:
Originally posted by Rotary:
Ok so you have 1080i and 720p but the 576p becomes 576i for a normal TV. I wonder if they could view it on a computer monitor and see the 576p?


COFDM has a QAM modulation so wouldn't it need a CATV tuner whatever that is. The description of COFDM says that it is Coded Orthongonal Frequency Division Multiplexing and the multiplexing means that it divides the one channel into 7000 channels and that in each one they have QAM. Which is similar to AM like AM radio?


But it doesn't have a satellite receiver like dish. That would make it cheaper.


Don't understand the bit about supply and demand. In England they have sold millions as part of a subscription service and the price is between $200 and $300 and they have been doing it for less time than we have. I don't see any advertising for them either. A very quiet demand. A very small supply.




[This message has been edited by jonlgauthier (edited 04-11-2001).]
 
1 - 14 of 14 Posts
Status
Not open for further replies.
Top