Canadian TV, Computing and Home Theatre Forums banner

1 - 20 of 58 Posts

·
Registered
Joined
·
508 Posts
Discussion Starter #1

·
Registered
Joined
·
8,292 Posts
^^^^
Antenna size. Lower frequencies mean bigger antennas. On the other hand, lower frequencies perform better in remote areas, where the radio has to cover greater distances. Which use has the greater need?
 

·
Premium Member
Joined
·
3,737 Posts
Wow — if this goes through, it would be a difficult situation for television.
You either drive broadcasters out of business by making them spend ever-higher sums of money on capital costs (new transmitters and broadcast antennas — again!) or making their OTA signals impossible to receive by forcing them to use VHF spectrum that's ill-suited for dense, urban markets.
Meanwhile, alternative technologies (mainly wide-area mobile internet) are free to gobble up previous and existing TV spectrum at will, without any thought to how much bandwidth they're hogging.
Absolutely unreal.
 

·
OTA Forum Moderator
Joined
·
24,867 Posts
Forced VHF Reassignment an opportunity?

A few "ifs"...

If we feel trepidation about re-occupying VHF-LO and VHF-HI with DTV using today's ATSC standard we would be absolutely justified, as the U.S. broadcasters have loudly and clearly shown (are you listening, Industry Canada?) with their low ERP assignment troubles.

If TV broadcasters are pushed back into the VHF ranges, it would be clearly necessary for the authorities to finance that process in some way. This actually represents an opportunity to revisit ATSC and it's capabilities. ATSC is not chiseled in stone, nor is it static. It has been in development since the early 1980s and has a fair amount of forward-thinking adaptability built into it. Further ATSC enhancements would attempt to address most or all of the technical problems in the VHF bands, while already existing ATSC capabilities can support greater services like MPEG4 and 1080p. Why not add those in such a big transition? How about increased co-location, with competing stations sharing the same major channel number yet in full HD on subchannels thanks to MPEG4? Whether private businesses would consider that kind of sharing or not, it is worth putting on the table.

For consumers the issue might not actually mean massive antennas for VHF-LO, as high ERP levels could mean satisfactory reception with quarter-wave elements (~4.5 feet length for channel 2). Of course deepest fringe areas would still want the old half-wave behemoths.

it is not too late to revisit some of the underpinning standards within the ATSC to embrace the latest technologies. A large-scale reassignment of VHF channels for DTV would represent a good chance to do it.
 

·
Registered
Joined
·
3,261 Posts
But don't forget that broadcasters want a piece of the mobile pie, too.
Look at CBC English's statement that they will forego VHF hi allotments in favour of UHF, because they want to be able to broadcast ATSC/MH for mobile use.
 

·
Registered
Joined
·
379 Posts
The problem is that no amount of mobile spectrum is never going to be enough. In fact I read in the Globe and Mail last week that some U.S. mobile carriers are actually looking to Canada for changes to pricing structure, as they're realizing unlimited data plans are putting too much of a strain on the existing networks.

The big problem I see with mobile Internet, etc. is that it is going to create a bigger digital divide than we've ever seen before. The rich socialite elites will have premium access to the best mobile 4G networks, while the masses will be lucky to have an SMS messaging-only device. Land lines are still the most efficient way of delivering the Internet, as far as I can tell.

I do agree, however, that some of the UHF band in the United States could be put to better use than it is being now. Too much spectrum being wasted on all-infomercial channels or networks like ION with rock-bottom viewership that would be better suited to cable. In Canada it would be easy to get rid of those stations (in fact I don't believe the CRTC even permits infomercial-only OTA stations), but the 1st Amendment in the United States presents an enormous challenge.
 

·
Registered
Joined
·
358 Posts
Couple of thoughts from south of the border:

Ultimately, you can't fight physics. With what seemingly were bad assumptions on the noise environment (or selective deafness to those who were trying to warn them), the FCC's propagation analyses underestimated what RF power would be necessary to replicate analog coverage. Additionally, with less noise, co-channel and adjacent-channel interference became more important, further putting limits on RF power.

There are precedents for accepting higher predicted interference in US broadcasting. Local AM stations (old Class IV, now Class C on frequencies like 1230, 1240, 1340, 1450, and 1490) started out as 250 watts full-time. Eventually daytime power was raised to 1 kW and stations had to accept any interference generated by such a move (in fact, Class C allocations are still made assuming 250 watt operation.) Finally, in an attempt to fight increased local noise, nighttime power was raised to 1 kW.

If VHF DTV power is raised with the acknowledgement that there will be more interference, it will take a while to figure out just how bad things are. From my casual review of filings where VHF stations have requested more power than would normally be allowed, predicted interference has rarely, if ever, shown up in measurements. So, one outcome might be improved urban (indoor) reception with some compromise to fringe reception, with that compromise to be determined later.

Trouble is, this is a really crappy way to re-do allocations.
 

·
OTA Forum Moderator
Joined
·
24,867 Posts
mjjl said:
some of the UHF band in the United States could be put to better use than it is being now
Undoubtedly true to many people, but I'd rather that we please stay focused here on the technical issues of this proposal facing broadcasters rather than the programming payload of stations. :)
 

·
OTA Forum Moderator
Joined
·
24,867 Posts
Dave Loudin said:
Trouble is, this is a really crappy way to re-do allocations.
Yep, with a lot of "not again!!!" sentiments about to be unleashed. Such is life in the amazingly rapid world of digital convergence.
 

·
Registered
Joined
·
3,396 Posts
While it might work for Rural America (which doesn't have a channel shortage problem to begin with),
it's a non-starter for nearly all Urban areas....the Hi-VHF channel slots are already taken.

Perhaps some would like to relocate to Ch2-6....and hope Ch5/6 aren't reallocated to FM Band....
That only leaves Ch2-4.....which can generate lots of 3rd order intermods into Lo-VHF band if FCC
increases power levels enough to overcome the Local Man-Made Noise, Indoor Rabbit Ears and
the alleged difficulty for VHF penetrating the walls of modern single family and multi-family buildings.....

Perhaps Low-Power Stations & Repeaters should be encouraged to use Ch2-4.....with considerable
savings on their monthly electric bill....
 

·
Registered
Joined
·
738 Posts
... If VHF DTV power is raised with the acknowledgement that there will be more interference, it will take a while to figure out just how bad things are. From my casual review of filings where VHF stations have requested more power than would normally be allowed, predicted interference has rarely, if ever, shown up in measurements. So, one outcome might be improved urban (indoor) reception with some compromise to fringe reception, with that compromise to be determined later.

Trouble is, this is a really crappy way to re-do allocations.
Increased power in the VHF bands requires that most stations in the band increase power to maintain the same Desired to Undesired (D/U) signal ratios. If every VHF station doubled power (+3 dB) then the D/U ratios remain the same and the interference will remain the same but the signal level will increase to the benefit of signal to noise limited viewers.

If more UHF spectrum is needed for wireless in major centers then it makes sense to use all 7 high VHF channels in those locations and use UHF farther out where the demand for wireless spectrum will be much lower based on lower population density. Reworking the spectrum assignments to maximize capacity for data while retaining the same number of television channels will be a major task. There are also some two-way radio systems allocated in channels 14 to 20 that could be moved to make more room for wireless data. Some of these radio assignments might be relocated in low VHF while other uses could be satisfied by public trunked radio systems and cellular.

In all these cases, the companies wanting to occupy the UHF spectrum must fund the other parties forced to relocate.
 

·
Registered
Joined
·
1,713 Posts
Another frequency transition so soon after just having one would be too much for broadcasters to accept and is poor government .Wireless will just have to work with what bandwidth they have.VHF low is almost useless for ASTC transmission.Poor building penetration in cities and poor response to static noises.
 

·
Registered
Joined
·
257 Posts
Agreed. NTSC standard is durable and compatible for 70 years. We haven't even switched to mandatory ATSC yet in Canada and there is already talk of shuffling the deck. MPEG 4? Let's just toss all those 1-10 year old TVs into the landfill.....
 

·
Registered
Joined
·
7,131 Posts
MPEG4 can be phased in easily over 5-10 years, similar to the way MGEG2 ATSC was phased in. Step 1, FCC mandates that all new TV and TV tuners sets meet new standards by a certain date. Since the new sets are backwardly compatible, there is no need to do anything further. Eventually, enough MPEG4 capable sets will be in the hands of consumers for broadcasters to launch new MPEG4 services. People with incompatible sets who want the new services can purchase add-on tuners.
 

·
OTA Forum Moderator
Joined
·
24,867 Posts
The "roll over" rate of technologies in the wireless mobile world is a good example of how flexible consumers can be when the "next best thing" contains direct benefits to them. Is anyone demanding that we stop at 3G? Of course not. 4G here we come! So, why should TV system changes and updates be any different?

As I've said, if an OTA channel re-transition is to take place it is an opportunity to give consumers better choices than ever, provided that backwards compatibility is maintained during the product overlap timeframe. This could be time well spent to make DTV better than ever, incorporating a lot of lessons learned with new capabilities such as MPEG4, 1080p, TrueHD 7.1, and other features. The ATSC standard has some ugly kludges in it (i.e. PSIP) that would benefit from a revisit/replacement.

A comment I've often made (as with many other people here and elsewhere) is that the mobile/wireless operators need to improve their use of bandwidth. Fair is fair, so the same should apply to DTV. So, as long as broadcasters aren't left having to pay for a re-transition (I agree with GeorgeMx's view on that) then this would be an ideal time to fold in a big improvement in DTV.
 

·
Registered
Joined
·
2,818 Posts
This topic brings up a very good question.
IF we moved to MPEG4 to fit more data in a smaller space, would existing tuners be compatible?
I mean, MPEG4's been in the ATSC spec for a couple years now.. would it not stand to reason that any tuner built since MPEG4 was added to the spec, be able to decode MPEG4?

If so, that only eliminates the very early adopters.
Whom, by the time we actually moved to mpeg4, will probably have replaced those devices (unless we're talking in the very near future).

And if this did happen, we'd probably have a few years' overlap just as we do now with analog-digital.
Only, maybe a UHF channel with mpeg2, and a VHF with mpeg4.
Or perhaps main+subchannel on the same physical channel, one mpeg2, one mpeg4.

This assumes it would require new hardware, of course.
It could be a simple firmware-only update, which means there's no issue at all!
 

·
Registered
Joined
·
4,459 Posts
I am not going to say for sure, but I would say quite a bit of gear is MPEG2 only.

Any PC based DVR, satellite based DVR which supports MPEG4 for satellite, and any HD TiVo model, can in theory support ATSC MPEG 4, if the modulation scheme stays the same.
 

·
Registered
Joined
·
6,257 Posts
IF we moved to MPEG4 to fit more data in a smaller space, would existing tuners be compatible?
AFAIK. Most if not all TVs and STBs will not decode MPEG4. As classicsat said, some satellite boxes and PC based PVRs might be able to do it though as they may already have MPEG4 decoder chips or else the software can be upgraded to do MPEG4 deciding (if the CPU is fast enough), though software decoding often isn't as good as hardware decoding.

would it not stand to reason that any tuner built since MPEG4 was added to the spec, be able to decode MPEG4?
No. Unless they are mandated to support it or they see a marketing benefit for adding it, manufacturers won't spend money to add new features.
 

·
Registered
Joined
·
2,818 Posts
I understand the 'bare minimum' piece
My point on that second part was more along the lines of "in order to call it an ATSC-compliant product, would it not be required to meet all aspects of the ATSC standard?"

Otherwise, what's the point of a standard if anyone can pick any piece of it that they want and still use the name?
 
1 - 20 of 58 Posts
Top