The official final DTV Table Of Allotments/channel change thread - Page 9 - AVS Forum

AVS Forum > HDTV > Local HDTV Info and Reception > The official final DTV Table Of Allotments/channel change thread

Local HDTV Info and Reception

AntAltMike's Avatar AntAltMike
01:25 PM Liked: 29
post #241 of 7380
08-23-2007 | Posts: 3,598
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Quote:
Originally Posted by GeorgeLV View Post

...As for an upper-VHF, unless the FCC allows 3 adjacent digital channels there's nowhere to put it given the current post-transition allotments.

7 - KLAS-DT
9 - KVVU-DT
11 - KLVX-DT
13 - KTNV-DT

They do if the towers are close to one another. In Washington, DC, we have channel 34 on one tower and 35 and 36 on the tower two blocks north of it, and 33 will be on one of those towers if it ever gets built. Channel 33 had initially been approved to be on a tower to be built on a lot adjacent to one of the others, but the tower construction authorization was revoked after it was half-built due to safety concerns (ice falling off that tower could land on Wisconsin Ave. traffic).
Falcon_77's Avatar Falcon_77
08:46 PM Liked: 10
post #242 of 7380
08-23-2007 | Posts: 2,602
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We have 41, 42 & 43 on Mt. Wilson.

What is the reason it is ok if they are close together?
Trip in VA's Avatar Trip in VA
10:18 PM Liked: 66
post #243 of 7380
08-23-2007 | Posts: 14,467
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Quote:
Originally Posted by GeorgeLV View Post

Reliable OTA reception of KVBC-DT is about as challenging as WBBM-DT in Chicago, that is, next to impossible. It's not a matter of signal strength so much as interference, anybody viewing from an OTA or DirecTV will experience intermittent breakups. (Cox Cable has a dedicated fiber feed.)

I'm surprised that KVBC's 27.7 kW signal is no better than WBBM's 4.4 kW signal. I'd imagine some improvement, though I can understand the continued interference problems.

Quote:


As for an upper-VHF, unless the FCC allows 3 adjacent digital channels there's nowhere to put it given the current post-transition allotments.

Three or more stations can be side-by-side. Note the other examples like DC.

@ HIPAR:

I hadn't seen that list in a while. I note that the FCC has added 16 to New York. I didn't remember some of these frequencies were on here.

*notes 15 in Cleveland*

*further notes WEWS-DT 15 Cleveland*

Uh-oh, I think the FCC made a boo-boo.

- Trip
Larry Kenney's Avatar Larry Kenney
02:33 AM Liked: 33
post #244 of 7380
08-24-2007 | Posts: 2,705
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Quote:
Originally Posted by GeorgeLV View Post

As for an upper-VHF, unless the FCC allows 3 adjacent digital channels there's nowhere to put it given the current post-transition allotments.

CHANNEL SPACING REQUIREMENTS - from the FCC web site:
Assignments on adjacent channels are permitted as long as the transmitters are within a 14 mile range.
Channels 7-13:
Prohibited on same channel: 0-170 mi
Prohibited on adjacent channel: 14.29-68.35 mi
Channels 14-51:
Prohibited on same channel: 0-139 mi
Prohibited on adjacent channel: 14.91-68.35 mi

Note on spacing requirements:
The "doughnut" shaped exclusion zone for adjacent channels recognizes
that adjacent stations only present a problem when there is a strong
station right next to a weak station you want to watch.

Larry
SF
greywolf's Avatar greywolf
12:19 PM Liked: 10
post #245 of 7380
08-24-2007 | Posts: 7,086
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Chicago has been running digital channels on 51, 52 and 53 successfully for years.
N5XZS's Avatar N5XZS
05:28 PM Liked: 11
post #246 of 7380
08-24-2007 | Posts: 1,174
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Just take a look at KNMD-DT "PBS" on channel 9 running at 200 watts ERP on Sandia Crest and KCHF-DT "REL" on channel 10 running at 30 KW ERP just 50 North miles or so.....

KCHF-DT for some reason is footdragging, by not moving to Sandia Crest mountain in order to let KNMD-DT to upgrade the TX power.

Both station are in Albuquerque's TV market DMA....

What you think it's gonna happen after the analog shut down date?

8-24-07
Calaveras's Avatar Calaveras
05:00 PM Liked: 107
post #247 of 7380
08-26-2007 | Posts: 3,176
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Quote:
Originally Posted by HIPAR View Post

My observation is that polarization is not preserved in the terrestrial environment. I suspect multiple specular reflections and scattering from vegetation, especially for UHF propagation, corrupts the original polarization.

Has anyone of you tried receiving 8VSB with a circular polarized antenna?

--- CHAS

I was wondering the same thing today after installing antennas for a friend yesterday only 17 miles from the antenna farm but looking through a stand of huge trees. Several of the stations are suffering some multipath and one is completely destroyed by multipath. My experience in ham radio with circular polarization at both ends over a non-line-of-sight path, is that CP wins hands down every time. I have not seen any real difference though over vertical or horizontal polarization if you have a true line-of-sight path. Unfortunately you need CP antennas at both ends and I doubt we'll ever see the broadcasters switching to CP antennas.

Chuck
foxeng's Avatar foxeng
06:15 PM Liked: 40
post #248 of 7380
08-26-2007 | Posts: 14,032
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Quote:
Originally Posted by Calaveras View Post

Unfortunately you need CP antennas at both ends and I doubt we'll ever see the broadcasters switching to CP antennas.

Transmit CP antennas were all the rage in the 70's until it was realized that there were no CP receive antennas and it was hurting coverage for the H pole antennas, so TV went back to horizontal polarization. The only time TV stations use vertical is in conjunction with horizontal (still the primary polarizaton) to counteract multipath due to mountains or other known multipath objects. Antennas can even be designed to radiate more H in one direction and more V in another to counteract multipath.
Tony Nx's Avatar Tony Nx
06:15 PM Liked: 10
post #249 of 7380
08-27-2007 | Posts: 23
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It is good to hear that in some areas there is a resurgance of outside antennas for OTA.

However here in the San Fernando Valley of Los Angeles all but hillside areas are mostly flat with Line-of-sight to Mt. Wilson, yet the retailers are telling customers they have to have cable or satellite to get Digital. A few retailers have a few rabbit-ear type indoor antennas labeled "For HDTV", but I have not seen any as good as the Silver Sensor.

Radio Shack and Frys carry only a few outside antennas. At Fry's they are in the electronics parts section, quite far from the TV section. My nearby Radio shack does not display any TV antennas. You have to ask, then after one clerk asking another if there is such a thing, one of them will dig around in the store room and bring one out.

Most people I have talked to about this react as if the idea of putting a TV antenna on their roof is preposterous. Seems to be thought of as some sort of tasteless 50's retro thing. Most Home Owner's Assn's forbid anything attached to the outside of the house. Although federal law prohibits such restrictions on TV antennas, home owners are afraid to annoy the HOA.

I too look at rooftops. Most of the few antennas I see in this area are either badly broken or pointed everywhere but at Mt. Wilson, looking like something not bothered to be taken down when they got cable. I don't see a real preponderance of Satellite antennas either.

Cable is juat what comes to mind when most people in this area think of TV, inspite of the superior service Satellite has provided.

I agree that if we called it "Wireless TV" more outside antennas would sprout. Or how about calling it "Free Wireless High Speed Streaming Video "! After all, it is all about marketing buzz words these days. Sell the sizzle, not the steak. We'd ust have to keep quiet about having been doing it for nearly ten years.

Meanwhile the people with the most to loose, the Broadcasters, are asleep at the switch, doing little to let pelple know they can get their HDTV broadcasts OTA for free.

Can you tell this bugs me?

Tony
Tony Nx's Avatar Tony Nx
06:31 PM Liked: 10
post #250 of 7380
08-27-2007 | Posts: 23
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On the subject of channel allocations, Keep in mind that OTA originally had channels 2 through 81. Few if any stations wanted to operate on those upper channels so it was not a great loss to give them up. There is also an attack on the broadcast spectrum in the 2GHz band, used for news gathering. Nextel has taken some of it, DOD wants some more and now even a chain of truck stops wants in on it!

Tony
Larry Kenney's Avatar Larry Kenney
02:47 AM Liked: 33
post #251 of 7380
08-28-2007 | Posts: 2,705
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Quote:
Originally Posted by Tony Nx View Post

Meanwhile the people with the most to loose, the Broadcasters, are asleep at the switch, doing little to let pelple know they can get their HDTV broadcasts OTA for free.

Can you tell this bugs me?

Tony

It bugs me, too, Tony. For example, you see the local stations promoting their HD broadcasts, but instead of saying it's on channel 5-1, they say it's on Comcast channel 705. Or if something is special on one of the digital sub-channels, they don't say to watch it on channel 7-2, they say to watch it on Comcast 195... or whatever the channel is. Is Comcast paying them to do this?

Lots of stores here in the SF Bay Area are telling people that they need cable or satellite to get HD programming, too.

Larry
SF
Falcon_77's Avatar Falcon_77
08:51 AM Liked: 10
post #252 of 7380
08-28-2007 | Posts: 2,602
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Quote:


I agree that if we called it "Wireless TV" more outside antennas would sprout. Or how about calling it "Free Wireless High Speed Streaming Video "! After all, it is all about marketing buzz words these days. Sell the sizzle, not the steak. We'd ust have to keep quiet about having been doing it for nearly ten years.

The UK "brand name" for OTA DTV (DTT) seems to be very successful:

Freeview

I was reading a consumer reports mag (from March '07 I think) while in Jury Duty yesterday. It compared the pros and cons of TV's and cable vs. satellite, while almost completely ignoring OTA. At least it showed which TV's had an ATSC tuner.

I sent the following article to local friends and family about the analog switch-off:

Senators worried about TV 'train wreck'

I didn't get a single response or comment. It just seems that people want to believe that HD is only available on Satellite or Cable, with fancy boxes. Perhaps one can't "keep up with the Jonses" by putting up an antenna?
MeowMeow's Avatar MeowMeow
09:19 AM Liked: 11
post #253 of 7380
08-28-2007 | Posts: 1,799
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From the standpoint of business relationships, there is no coin in promoting OTA television. And even if there was, how many store associates really intend to waste their time explaining that OTA digital is not just superior to old school NTSC, but to cable and satellite?

Think of every single barrier to adoption you have to overcome:

1. OTA television sucks. Lots of people still remember static in their reception.

2. Anything we pay for is super-duper, even if we totally get screwed by evil corporations.

3. Just buy a normal antenna, seriously!! No, seriously. Really. Yes, a normal antenna. A normal one. Which then trends back to #1 issue.

4. What? This might involve work? On my roof? Screw that!!


Honestly, OTA enthusiasts need to hold parties where they sit people down and show them how awesome it is.

My oldest nephew thought I finally gave up the fight and went to cable when I showed him the reception and the guide. And then I said, "This isn't even the best stuff. The best stuff is the NFL. You can see the flecks in the paint in their helmets."

Then his next question was, "You bought an HDTV antenna?" Then I had to explain the whole UHF thing.

There is interest in all of it. One of my mom's co-workers asked me about it a while back because he lives in the middle of nowhere and doesn't want to shell out for dish. He's one of the legion of people like me who will adore OTA as long as the NFL adores it, too.

But, we're not going to be able to depend on some ignorant kid working in the electronics section to go out and convert followers to OTA HDTV. We're going to have to do ourselves.

The upside is we have a great pitch: Look at that friggin picture!!!
HIPAR's Avatar HIPAR
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post #254 of 7380
08-28-2007 | Posts: 465
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Customers subscribe to cable and satellite because they want to watch HBO, CNN, Discovery and the list goes on. Oh yes, throw in the locals since they are available with the 'package'. So, who needs an old fashioned fifties era TV antenna anymore?

I was once told by an very young 'associate' at Circuit City there is no such thing as over-the-air television. I think he actually believed that. Look around .. there are lots of us around who can't remember when there were no cell phones or PCs and when you needed an antenna for television.

With the broadcasters, towers and transmitters are an annoying part of the cost of doing business allowing them secure carriage from the cable and DBS operators that actually reach 85% (maybe 90% after the train wreck) of the viewers.

--- CHAS
dline's Avatar dline
12:15 PM Liked: 10
post #255 of 7380
08-28-2007 | Posts: 2,113
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If there's a somewhat ironic ray of hope, it's in the stations which are in retransmission disputes with the cable companies. A case in point: Hearst-Argyle-owned KETV in Omaha is in a dispute with Cox Cable and won't let Cox carry their digital signal. That provided KETV with a golden opportunity to let viewers know, through their website (and probably elsewhere), that you don't need cable to get the station in HD. Sinclair stations also had this issue for a long time, but unfortunately they chose to muddy the waters by encouraging Mediacom subscribers to switch to D* when the dispute extended to the analog channels.

The downside is that this route closes when a retransmission agreement is reached.
Rick0725's Avatar Rick0725
01:55 PM Liked: 11
post #256 of 7380
08-28-2007 | Posts: 670
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Quote:


Think of every single barrier to adoption you have to overcome:

1. OTA television sucks. Lots of people still remember static in their reception.

2. Anything we pay for is super-duper, even if we totally get screwed by evil corporations.

3. Just buy a normal antenna, seriously!! No, seriously. Really. Yes, a normal antenna. A normal one. Which then trends back to #1 issue.

4. What? This might involve work? On my roof? Screw that!!

this is why I abandoned my business in the early 1990's...I saw the handwriting on the wall years before that in 80's. cable and satellite grew tremendously in market shares. there was business in the boonies but it cost to much to get there and make decent money.

only problem with #4 .

cable and satellite installation and equipment is free so to speak.

antennas are big and ugly, not everyone has the expertise to get the job done, there are not many antenna installers around anymore, installations are not cut and dry , inside installations are problematic, the entire united states is not flat, there are too many variables with reception, too many opinions on equipment selection, antennas are not an exact science, startup costs are high, not all stations transmit in hd... and you need a ladder.

there are pockets of interest for off air around the country but I do not see antennas as viable business any longer.

there are just too many options today. unlike the old days where you just o had newspapers, off air tv, and movies.

today you have the internet, satellite, cable, directv, dish network, blockbuster, ipods, on and on.
Nitewatchman's Avatar Nitewatchman
12:10 AM Liked: 18
post #257 of 7380
08-31-2007 | Posts: 6,292
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We have DTV operations on first adjacent channels 28,29,30,31,33,34,35,50,51 in Dayton/Cincinnati, all but ch 30(Dayton) and 50,51(Dayton) in that list being in Cincinnati. 28+29, and 34,35 being co-located, all of the Cincinnati towers involved being within a few miles or so of each other, all of Dayton towers being on the same "antenna farm".

There is also Analog9/digital 10(co-located) in Cincinnati as well as a few other first adjacent channel relationships with LP's. 24 Covington KY(cincinnati)/25 LP cincy, 40LP analog dayton/41 digital, 39digital(COL Richmond, IN)( transmits from just N of cincinnati/38 A LP cincy ... So far, at least from what I've heard for the MOST part it seems to be working out quite well.

Quote:
Originally Posted by Larry Kenney View Post

CHANNEL SPACING REQUIREMENTS - from the FCC web site:
Assignments on adjacent channels are permitted as long as the transmitters are within a 14 mile range.
Channels 7-13:
Prohibited on same channel: 0-170 mi
Prohibited on adjacent channel: 14.29-68.35 mi
Channels 14-51:
Prohibited on same channel: 0-139 mi
Prohibited on adjacent channel: 14.91-68.35 mi

Note on spacing requirements:
The "doughnut" shaped exclusion zone for adjacent channels recognizes that adjacent stations only present a problem when there is a strong station right next to a weak station you want to watch.

Larry
SF

I think in at least some cases It turns out to be a little more complicated than that ...

Those rules as are specified in more detail here in CFR 47, $76.623 apply to applications for new DTV allotments or changes to DTV allotments.

What was used by FCC in the 90's to develop the original DTV table of allotments was apparently a little more lienient than that in at least some circumstances.

So, how does what happened for the "original" DTV allotment table apply to the post-transistion situation?

For one thing, because, most stations which elected to remain on their Current DTV channel assignment are going to be using the same facilities post-transistion as they are now.

Here's an example. WXIX-DT 29 Cincinnati, WRGT-DT 30 Dayton. Their transmit sites are about 44 miles apart. Both will be remaining where they are now, presumably with the same facilities they are using, now.

In the first round of elections, WRGT-DT DID at first file an election form to move to their analog channel, 45 post-transistion. However, they soon received an interference conflict notice from FCC. I have no idea what that letter said, but I would guess it might involve an interference conflict with WXIN-DT 45, Indianapolis, which elected to keep their digital where it is now, on 45.


Here is WRGT-DT's predicted 41dbu service contour map from FCC site :

http://www.fcc.gov/fcc-bin/FMTV-serv...=DT421344.html

Here is WXIX-DT's predicted 41dbu service contour map from FCC site :

http://www.fcc.gov/fcc-bin/FMTV-serv...=DT518618.html

Notice that areas to the South of WXIX-DT transmit location, and areas to the North of WRGT-DT transmit location are in the predicted service area of BOTH stations.

I haven't had the time to do so yet, but I have contemplated going to www.tvfool.com and plugging in some receive locations within the service contour of both stations, but just to the North of WRGT, and just to the South of WXIX and see what it predicts for either of those stations, the interest being the difference between the two .... somehow, I would not be surprised if in some locations the difference may be very close to, or exceed the D/U ratios for 1st adjacent channel DTV specified by FCC ...

I do know that of least one viewer, about on WXIX-DT's 41dbu contour+Just north of WRGT's tower has reported issues that seemed to have began when WRGT-DT went from using a ~15KW ERP STA to 425KW ERP full power operation ... He also reported the same regarding reception of WKRC-DT 31 Cincinnati, which will be moving to 12 after analog shut off ...
---------

Its water under the bridge, now, but Personally, I feel this particular example demonstrates a fallacy in the rules that governed the channel election process. Here's why ..

For one thing, because, in some cases, stations are staying "put" on channel assignments which were allocated as part of the "orignal" DTV allotment table, on possibly less than desireable assignments during the transistion, less than desireable in some cases perhaps because of the fact the orignal DTV table of allotments were developed for "during the transistion" when BOTH analog and digital stations were on the air, and the "crowded spectrum" nature that implies also implies that it was necessary for FCC to "cut corners" in some places so all stations would "fit" during the transistion ...

For another, for example, In this case of WXIX and WRGT, since neither of the stations "aren't moving from where they are", per the channel election rules, both stations are just "fine and dandy" where they are ... However, if either station wanted to move to their analog channel assignment(which WRGT tried), they would have to protect OTHER stations, such as for example, WXIN-DT 45 Indy, and WBKI-DT 19 (19 is WXIX's analog channel) Campbellsville, KY ... So, in other words, there are problems for them either way ..

And, in a sense, since the channel election rules basically said that stations remaining ON their current DTV channel had full interference protection, and stations moving to their analog channel assignments would have to PROTECT other stations(with stations with out-of core digital channel assignments given some "lieniency/preference" in this regard) Tsome(or many?) stations were probably "discouraged" from moving to their analog channel assignment for that reason ..

How unusual this particular example of WXIX-DT and WRGT-DT is, I have no idea ....
MeowMeow's Avatar MeowMeow
09:52 AM Liked: 11
post #258 of 7380
08-31-2007 | Posts: 1,799
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Quote:
Originally Posted by Rick0725 View Post

antennas are big and ugly, not everyone has the expertise to get the job done, there are not many antenna installers around anymore, installations are not cut and dry , inside installations are problematic, the entire united states is not flat, there are too many variables with reception, too many opinions on equipment selection, antennas are not an exact science, startup costs are high, not all stations transmit in hd... and you need a ladder.

Let me add:

#5: This requires thinking? I barely passed Algebra I.
Nitewatchman's Avatar Nitewatchman
12:56 PM Liked: 18
post #259 of 7380
08-31-2007 | Posts: 6,292
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I am curious to know how the issues regarding excuses why people don't use antennas have anything to do with the Final DTV table of allotments .....

I will say this ...
As for broadcasters transmitters+towers and the like being "hinderance" to them other than to help them secure cable or satellite carrige ... Broadcasters who feel that way(and I do know some of them do feel that way, maybe even many of them) to the extent it effects their OTA service really shouldn't be allowed the privilage to use our public airwaves, IMHO .... Better things can be done with it ...
MeowMeow's Avatar MeowMeow
03:06 PM Liked: 11
post #260 of 7380
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Quote:
Originally Posted by Nitewatchman View Post

I am curious to know how the issues regarding excuses why people don't use antennas have anything to do with the Final DTV table of allotments .....

I'll quote myself, annoying though that may be to others...

Quote:


From the standpoint of business relationships, there is no coin in promoting OTA television. And even if there was, how many store associates really intend to waste their time explaining that OTA digital is not just superior to old school NTSC, but to cable and satellite?

But, yes, we have diverged. My apologies. I was just trying to make a small point earlier that OTA needs all of us making a more active effort to create converts if we love it so much.
Nitewatchman's Avatar Nitewatchman
03:58 PM Liked: 18
post #261 of 7380
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Quote:
Originally Posted by MeowMeow View Post

My apologies.

No need to apologize ... I wasn't "singling anyone out" in particular, just saying it seems to me we've wondered a bit too far off topic, as there are other threads(or a new one if necessary) which seem to me would be more appropriate places to discuss those issues .. As I just can't seem to see how "how many people use antennas" and why they don't/etc, has anything to do, or even remotely relates to the "DTV table of allotments" ....

Quote:


I was just trying to make a small point earlier that OTA needs all of us making a more active effort to create converts if we love it so much.

Good point ... IMHO, I would say that OTA needs the broadcasters making a more active effort in that regard ... It needs the retailers too, but for instance, if the broadcasters *really wanted* to, they could do something about that as well ... Imagine a news report examining which retailers in the area have DTV receivers or antennas available, or on display, or antennas on their roofs(like TV stores USED to have in the 70's and early 80's when I was growing up) to help demonstrate OTA TV .... Imagine a FM station in the late 60's or early 70's that "didn't care" whether or not retailers had FM receivers available .... Yeah, I know why it's that way ... Satellite and cable, that's not my point -- OTA broadcasting *is* the actual business OTA broadcasters are in, and if they don't want to *BE* broadcasters, well, see my last post .....

I know I(and probably most of us here who care about these things) do what we can to "promote" OTA ... But I don't see that much from broadcasters, on the air ... Do see some of it though ... for instance, one of our local broadcasters recently began doing HD local news broadcasts, and the first day of HD local news from them when they talked about it, one of the first things they mentioned was receiving their HD digital broadcasts OTA with an antenna .... It got "top billing" over the info they provided for cable or satellite reception of their digital station (and their digital station IS carried on local cable systems in HD as well as via D* LiL) ....

That being said ...From what I have seen, We have groups such as NAB+MSTV looking after "OTA" and OTA TV broadcasting in many aspects related to congress and FCC ... From what I've seen, the "posisition" those groups take, and also what broadcasters interests are, *usually*(but not allways) also *just happen* to conicide with what is of interest to OTA viewers (things they are interested in that *allow* broadcasters to provide we OTA viewers with good service) ... HOWEVER, I do often wonder if it also would be a good thing if we OTA viewers(especially perhaps OTA HD viewers) had our own "group" looking after our interests, rather than "other groups" which seem to think they have our interests at heart (mostly involving farming, senior citizens, low income people/etc) ...... There just doesn't seem to be a group like that looking after our interests in congress or submitting comments to FCC on various DTV rulemaking proceedings ...

Of course, probably none of us (and certianly not me) have the time or motivation to organize some sort of "grassroots effort" for something like that .....

See, I can make Off topic posts too (sorry
MeowMeow's Avatar MeowMeow
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We're all good. I suspect we're somewhat off-topic because we're sorting of waiting that last settling of the DTV allotments.

For my part, to be on-topic, I'm most worried about the government rendering a final decision about white space devices in the DTV ranges. I'm still fairly hopeful that when the number of channels drops nearly in half with the analog shutdown that we're going to see a significant reduction in interference.

The nice thing is it looks like we're finally coming to a conclusion. I'd be surprised if Feb 2009 is not now set in stone.
foxeng's Avatar foxeng
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Quote:
Originally Posted by MeowMeow View Post

I'd be surprised if Feb 2009 is not now set in stone.

It has been set in stone for a while now. This is the result of that. No one is talking about a delay and hasn't been since the bill was signed. Everyone in government wants this done so they can stop talking about it.
milehighmike's Avatar milehighmike
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I have a couple of questions for the experts that have been posting to this thread:

1. Would it have been wise for the FCC to have required stations broadcasting from the same antenna farm (or, say, within 10 miles of each other) to use continguous channels, such as 19, 20, 21, 22, etc. for their final digital channels? It seems from reading threads like this one that some of the interference issues would not have occurred and there would not have been the problems with WBBM and WABC finding a "home" and the low VHF 6 assignment for WPVI. I'm thinking that maybe the stations were given too much freedom to pick a final digital channel which is part of the problem of potentially limited availability of channels in some geographic areas, particularly the east coast. If the channels were contiguous, there wouldn't be, for example, unused channels in-between occupied channels that can't be used due to co-channel interference. Just a thought.

2. Could someone explain what horizontal, veritical, and circular polarization is and why it seems television seems to have settled on horizontal?
Larry Kenney's Avatar Larry Kenney
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Quote:
Originally Posted by milehighmike View Post

1. Would it have been wise for the FCC to have required stations broadcasting from the same antenna farm (or, say, within 10 miles of each other) to use continguous channels, such as 19, 20, 21, 22, etc. for their final digital channels?

We have such a situation here in the San Francisco-San Jose market. There are four stations transmitting from the hills above Fremont, all within a mile or two of each other, on channels 49, 50, 51 and 52. After February, 2009, 49, 50 and 51 will remain. 52 has to move, since it's outside the new band, and will be going back to it's analog channel 36.

We'll also have several channel groupings for the stations transmitting from Sutro Tower in San Francisco after the analog shut down. We'll have 29 and 30, 33 and 34, 38 and 39, and 43, 44 and 45.

Larry
SF
foxeng's Avatar foxeng
07:21 AM Liked: 40
post #266 of 7380
09-01-2007 | Posts: 14,032
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Quote:
Originally Posted by milehighmike View Post

1. Would it have been wise for the FCC to have required stations broadcasting from the same antenna farm (or, say, within 10 miles of each other) to use continguous channels, such as 19, 20, 21, 22, etc. for their final digital channels?

The issue that really has formed the post transition channel line up is rooted in the analog world. From the start, the FCC had to protect analog stations on the air during the transition. They plugged digital stations in where there was spectrum space that would not cause undo interference with existing analog stations. Hence the reason for some stations getting directional digital patterns when their analog patterns were omni. In some areas they could allocate contiguous channels and not cause undo interference and did.

Fast forward 10 years, and we are now looking at the final Table of Assignments. In that 10 years, the FCC back slid about stations being able to go back to their analog channels, changed interference criteria, seemingly on the fly. Denying some stations the channels they elected with interference being stated as the reason even after stations submitted evidence to the contrary, but allowing other stations to increase interference to existing digital stations, also seemingly on a whim.

The question becomes the cost of many stations having to build out on digital channels, just to be told they will have to build again to get on contiguous channels. The political backlash from a move like that would have been huge because you are talking hundreds of thousands of dollars for the easiest moves.

I personally believe that once the dust settles and we have actually turned off the analogs, a number of stations will ask to change channels to gain coverage and you may see stations co-locate to tower farms to save money and they will ask for contiguous channels, but probably not in the numbers you would like to see.

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2. Could someone explain what horizontal, veritical, and circular polarization is and why it seems television seems to have settled on horizontal?

The difference of the polarizations is the angle at which the signal travels over the surface of the earth. Horizontal travels flat, just like you see TV antennas now. Vertical travels at right angles to the earth like you see in CB antennas and AM antennas on cars. CP travels in a helical spiral pattern but there are two pols with this mode as well. Left hand and right hand rotation. Each mode gives about 20 db of isolation from each other. Meaning a horizontal signal received on a vertical antenna is 20 db lower in signal strength than the same signal in the same location at the same receive height being received by a horizontal antenna.

Each 3 db you either half the signal strength or double the signal strength, depending on which way you are moving. So if you start out with a 100 watt signal and you insert 20 db of loss, it is same thing as a 0.78125 watt signal! That is why sats use the different pols. It allows them to use the channels twice. Once in the vertical pol and once in the horizontal pol to maximize the spectrum use.

As for the reason why TV uses horizontal, my guess would be because all broadcasting started out in the horizontal mode, including AM, and where there was a need to change pols for AM and FM radio, being the vertical receive antennas on cars, particularly since a 1/4 wave antenna on AM is around 200 ft long, that was never the case with TV, even though CP does do a better job for TV than horizontal. Even today on FM, many transmit antennas are made with both vertical for cars and horizontal for home listening with TV/FM antennas. By the time it was decided what to do with TV (in the 70's), the horizontal receive TV antenna had been in use almost 30 years and to get people to change would have been a nightmare so it has remained horizontal. There was talk early on to make digital TV CP but it never gained the needed traction because you then ran into the debate of which CP pol, left hand or right hand would become the standard and what would happen if someone bought the wrong CP mode antenna? Once the CP antenna is made in one direction, it can't be easily changed unlike the current antennas that you just rotate 90 degrees to change from one pol to another.

All of the issues that people bring up here were WELL debated back in the beginning and many were compromises to keep things moving. Yep, management by committee all the way!
HIPAR's Avatar HIPAR
08:36 AM Liked: 10
post #267 of 7380
09-01-2007 | Posts: 465
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Quote:
Originally Posted by milehighmike View Post

I have a couple of questions for the experts that have been posting to this thread:

2. Could someone explain what horizontal, veritical, and circular polarization is and why it seems television seems to have settled on horizontal?

Way back when, when scientists were trying to understand the mysteries of electricity and magnetism, there was evidence that the two could be related. When James Clerk Maxwell presented his equations the foundation for all things electromagnetic was established.

When an electrical charge is accelerated through a conductor by an electric field, there is an associated magnetic field generated. The magnetic lines are perpendicular to the electric field.

Now when the charge is accelerated back and forth through the conductor with a frequency, some neat things happen. As electric lines of force build to a maximum, decay to zero and repeat the process with opposite polarity, the magnetic lines go through the same process except their maximums occur when the electric lines are at their minimum. Energy is being transferred back and forth between the electric and magnetic fields.

Somehow, a distant conductor under the influence of this system is able to extract energy from the fields and guess what, actual power is transmitted through space. Maxwell can even tell you how fast the energy propagates based upon the properties of the transmission medium. We see the light and watch over the air TV.

How does all of this get involved with polarization. By convention we say the signal is polarized in the direction of the electric lines of force.

So, brush up on your vector calculus and work out a few boundary conditions to observe what happens when signals are reflected.


Blame it all on Maxwell, a very great man.

--- CHAS
Nitewatchman's Avatar Nitewatchman
12:40 PM Liked: 18
post #268 of 7380
09-01-2007 | Posts: 6,292
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Quote:
Originally Posted by MeowMeow View Post

For my part, to be on-topic, I'm most worried about the government rendering a final decision about white space devices in the DTV ranges.

Those who haven't seen it might want to read this document, A FCC report and order on the issue from 2006 :

http://fjallfoss.fcc.gov/edocs_publi...C-06-156A1.pdf

In that document, among other things they excluded channel 37(used for radio astronomy), and ch 52-69(which won't be "broadcast" spectrum) from use by the unlicensed devices. There is also additional discussion about excluding channel 2~4 and channel 14~20, but they haven't made a decision in that yet.

Here's some more of what it says that is of particular interest, paragraphs 16~18 :

Quote:
Originally Posted by FCC Report and order on unlicensed devices in Broadcast TV bands View Post


16. In order to provide sufficient time for the Commission and industry to develop appropriate technical standards for TV band products as well as lead time for industry to design and produce new products, we intend to adopt a Second Report and Order specifying final requirements for devices in the TV bands in the fall of 2007. This will allow the Commission’s Laboratory to begin accepting applications for certification of these devices in the TV bands by late 2007. Certification will be granted if the application, upon review, is found to comply with the new technical rules and will allow the manufacture and shipment of products to distribution points. However, as we discuss further below, these devices will not be allowed to be available for sale at retail until after the DTV transition ends on February 17, 2009.

17. We are convinced based on the record in this proceeding that we can adopt rules to allow fixed low power operation on unused spectrum in the TV bands without causing harmful interference to authorized services. There are several factors supporting this conclusion. First, upon completion of the DTV transition, there will be significant unused TV spectrum available in many areas in the country, either because of the separations required between authorized stations to avoid interference or because available TV channels have not been assigned and other services are not using vacant channels. Also,based on our experience in developing rules for U-NII devices, we believe it is reasonable to expect that existing technology, such as that used for spectrum sensing, can be adapted to allow devices to identify unused spectrum in a given geographic area and thus allow sharing of the TV bands. Further, we note that the IEEE 802.22 working group with broad based support is in the process of developing a standard to enable fixed devices to successfully share spectrum with authorized services in the TV bands. Finally,
these devices will operate at relatively low power levels and, as several commenters noted, it is easier to protect incumbent operations in the TV bands, including wireless microphones, when devices are limited to fixed operation.

18. Non-fixed devices (e.g., personal/portable devices as discussed in the Notice) generally pose a greater risk of harmful interference to authorized operations than fixed devices because such devices may have antennas that are less efficient and may be in a less advantageous position for sensing of incumbent transmissions (e.g., in a room versus on a 10-meter mast), especially given that they will change location, thus making reliable identification of unused frequencies substantially more difficult. Also, it may be difficult for TV and other users to locate a non-fixed device that causes interference because it frequently changes location, whereas a fixed device that causes interference can be located more easily. Further, we
note that the developing IEEE 802.22 standard is, at least at this time, limited to fixed point-to-point and point-to-multipoint operations and does not address the non-fixed personal/portable class of devices that the Commission proposed to allow in the Notice. We therefore find that additional information is needed on whether and how personal/portable devices can use spectrum sensing or other techniques to identify unused frequencies. More generally, we ask parties responding to the Further Notice to address whether and how non-fixed unlicensed devices could operate in the TV bands under the different sharing schemes under consideration in this proceeding.

I certianly am not even convinced they "can adopt rules to allow fixed low power operation on unused spectrum in the TV bands without causing harmful interference to authorized services." ....

We'll see what the rules they "intend" to adopt on this in Fall 2007 say, I suppose ...

What they've done with BPL doesn't increase my confidence in FCC regarding this matter, either ....
MeowMeow's Avatar MeowMeow
01:20 PM Liked: 11
post #269 of 7380
09-01-2007 | Posts: 1,799
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In addition, the final rules we adopt will allow the marketing of TV band devices to commence on February 18, 2009, after the transition to DTV service is complete and all TV stations are in operation on their permanent DTV channels.

Sounds like they've already made a decision.

It's a bad idea. Y'know, because it really sounds like a bad idea.

- - -

I want to toss a question about this whole notion of spectrum sensing that the FCC mentions. The idealized version goes that devices automatically scan the air and detect for TV signals in those bands. Can this even remotely work?

My first thought is, would any commercial grade portable device actually have any receive mechanism sensitive enough to dig out OTA TV signals in a normal situation? Half the time my antenna and tuner have to a hard time with this, and they're built to care about finding the signals. And they're up on the roof.

Are they really claiming it will be feasible for a laptop inside a building to sniff out an OTA signal at or even below ground-level? Cost-effectively?

Does anyone really think that some company in China is going to give a rat's ass about compliance with this? These people put lead paint on kids' toys! They're not going to care whether their device interferes with my antenna.

This whole idea is a heap of trouble waiting to happen.
Nitewatchman's Avatar Nitewatchman
01:37 PM Liked: 18
post #270 of 7380
09-01-2007 | Posts: 6,292
Joined: Dec 2001
Quote:
Originally Posted by MeowMeow View Post

Sounds like they've already made a decision.

That was my impression -- For the FIXED devices, jury's still out on the non-fixed devices(that's what the recent prototypes tested by FCC were which failed to properly locate DTV broadcast signals in the test, non-fixed devices) ... They just haven't come up with exactly HOW they're going to do it, yet .... We should find out soon ...

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It's a bad idea. Y'know, because it really sounds like a bad idea.

It *is* a bad idea because it is a bad idea

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