FCC: DTV Re-Transition To VHF Bands Now Being Touted - Page 3 - Canadian TV, Computing and Home Theatre Forums

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post #31 of 58 (permalink) Old 2010-11-11, 10:34 PM
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Quote:
Originally Posted by frontpl8
The other thing is there is only 12 Vhf channels
That's precisely why we got side-tracked with MPEG4 discussion as a means to cram several HD sub-channels into each of those 12 channels.

Now we're back to the essential wisdom, folly, or bore of shifting stations from UHF to VHF-LO and VHF-HI to give the Mobile/Wireless world more bandwidth.
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post #32 of 58 (permalink) Old 2010-11-11, 10:39 PM
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There is no way 12 channels will be enough. The Detroit area has literally dozens of stations that overlap. Toronto/Buffalo would be another problem area. There are, no doubt, others.

Quote:
...to give the Mobile/Wireless world more bandwidth.
The issue is one of money. Wireless telecom users and companies have lots of it while OTA users and TV stations don't. Money buys influence in US politics. Guess who put the bug in the FCC's ear and has the money to get their way.

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post #33 of 58 (permalink) Old 2010-11-11, 10:45 PM
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You're hitting on one of the missing ingredients in the FCC discussions so far... how many UHF channels would be chopped? Clearly their simplest formula would be lopping the top 12 off of UHF (in locations where there are no VHF stations already). Goodbye channels 40 through 51! 48 more free MHz for the Mobile/Wireless world.
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post #34 of 58 (permalink) Old 2010-11-12, 12:45 AM Thread Starter
 
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Already there are not enough channels to properly accommodate all the stations currently crammed in around western Lake Erie.

Taking anything more away would doom OTA U.S reception on the Canadian side of the border in a pathetic co-channel disaster and/or require US stations to install severe nulls for protection from each other. I can't imagine broadcasters going for the idea of piggybacking together on one RF channel in crap SD either, like in Detroit where the majority of digitals are above UHF 40 currently.

The VHF band is already packed with 5,7,8,9,10,11,12,13 already in use in southeastern MI,NW Ohio, Northern, OH. Low band would be terrible here. A jam packed FM band here sure wouldn't help the shift either. I have personally already lost a previously reliable Cleveland channel (WJW ch8 at 11kw ND ERP) at a distance of 68.5mi southeast to a new low powered (WUDT ch8 at 0.3kw ND ERP) station in Detroit at 38mi northwest.

WJW used to be available pretty much 24/7 for my entire life in analog and continuing in digital 8 starting in 06/2009, until the low power station signed on this past Apr. Now I really can't get either of them at all, even with proper antennas/gear.

If this push to VHF ever becomes mandatory at some point, I would hope they test the waters in more rural areas first where VHF would be a better fit.

52-83 are already gobbled up. How about use that chunk more efficiently first and if there still isn't enough a few years down the road, then maybe there can be another "digital transition" when equipment is more plentiful and cheaper. As for right now it's just too soon to screw with the current transition, especially in those areas that still aren't completely done with it yet.

my $0.02
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post #35 of 58 (permalink) Old 2010-11-12, 01:34 AM
 
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My Wade VIP-306 VHF 2-13 antenna just might have a use after-all . IMO, if the broadcasters move back to VHF exclusively it will effectively kill OTA as a legitimate television viewing option.Even if the signals are of decent strength, instead of a small UHF antenna, people will require a LOT more metal over their roof to now get all their channels. Most apartment and city dwellers will be in the "do not even bother" category.

Moving the digital OTA channels to VHF (with half being the Low band) will relegate OTA primarily to hardcore enthusiast's only, and be the final nail in the coffin for any chance of ATSC acceptance by the masses. If it IS done, at the very least, the parties who stand to profit the most, should foot the complete bill to cover the change over costs. Perhaps they should also reimburse all these recent UHF antenna purchases The last part was a JK, uhm then again perhaps not.
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post #36 of 58 (permalink) Old 2010-11-12, 01:51 PM
 
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The easiest solution to all of this. Is to reduce bandwidth of a station. The simple act of changing Mhz from 6 to 5. Would increase the total number of channels from 32 to 46. Plus there would be the added benefic of one more channel for VHF-hi.

The real solution is to increase TV channels somewhere. Maybe adding new RFs after VHFhi or before UHF band and reducing Bandwidth.

But If US expands the RFs for TV. A law would need to be pass. For all new TVs would need to support the new RFs asignments. Otherwise any stations on these new RFs will lose tons of capital.

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post #37 of 58 (permalink) Old 2010-11-12, 03:26 PM
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Originally Posted by GeorgeMx View Post
Another solution to the VHF problem is on-frequency repeaters. Significant research has been done in Ottawa on this technique as a means of filling coverage gaps. Repeaters increase capital and operating costs but if the value of the UHF spectrum is high enough, the wireless companies should be prepared to pay.
On frequency repeaters would certainly go a long way to reduce the amount of spectrum needed for TV since the contours (if set up as an SFN) would be permitted to overlap each other without worrying about interfering with each other. This alone may not completely solve the problem, but it certainly would be one piece of the puzzle.

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post #38 of 58 (permalink) Old 2010-11-12, 03:29 PM
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Originally Posted by Emerald_Boar View Post
The easiest solution to all of this. Is to reduce bandwidth of a station. The simple act of changing Mhz from 6 to 5.
Easiest solution??? That would obsolete every transmitter and receiver and require every station in the entire continent change at exactly the same time to avoid partial co-channel interference. Not what I would call an easy solution.
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post #39 of 58 (permalink) Old 2010-11-13, 02:26 PM
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I wonder what effect VHF DTV ingress will have on analog cable channels? Or for that matter, QAM signals once analog cable (2-13) transitions to digital?

My gut tells me that it wouldn't be as bad as analog broadcast signal ingress into cable systems....

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post #40 of 58 (permalink) Old 2010-11-15, 04:25 PM
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I wonder what effect VHF DTV ingress will have on analog cable channels?
I would expect it will have much less effect than broadcast analog as the biggest problem is the tuner having dificulties differentiating between the broadcast and cable signals.

Quote:
Or for that matter, QAM signals once analog cable (2-13) transitions to digital?
Should that ever happen (I suspect VHF and mid-band will stay analog for some time to come), it would likely be even less of a problem.

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post #41 of 58 (permalink) Old 2010-11-15, 06:44 PM
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I suspect that in both cases (ATSC ingress to NTSC cable or QAM), generally the result will be a lower CNR on those channels. I'm guessing it won't be noticeable, except if the cable signal level is already too low. ( I say generally, because obviously if you are very close to an ATSC transmitter, the OTA signal can still swamp the the cable signal if there is a gross problem with the cable wiring or terminations.)
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post #42 of 58 (permalink) Old 2010-11-15, 08:12 PM
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Quote:
Originally Posted by tvlurker
if there is a gross problem with the cable wiring or terminations
or also... if the TV receiver itself (and circuitry inside) are not sheilded very well from signals from the outside.

In Ottawa, on analog cable, a while ago (maybe a year ago), the cable providor moved PBS - the Public Broadcasting channel, from analog cable 64 to analog cable 97.

[PBS remained on digital cable 64 ... but that's not related to my point here.]

Guess what? Analog cable 97 is in or very near the FM band (!)

I have a small older CRT TV, and PBS on analog cable ch 97 on this TV has some picture interference. I assume this is some FM signals interfering - thru the TV (not the coax cables or connectors).

On a different TV receiver, same place, off same splitter - the picture is more clear - on analog 97.

I assume the difference is due to interfering signals (FM?) getting into the small CRT TV or it's internal circuitry ... more.

Are consumer TV's well sheilded these days ? In older days?

So here is an actual real example, I believe, where external signals are degrading the picture ... interfering with cable tv signals

Not that much ... still pretty viewable ... still ok... but enough.

It's real ... it happens.
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post #43 of 58 (permalink) Old 2010-11-15, 08:36 PM
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That wan't my point. Analog FM and TV signals, even at a very low level, will produce recognizable interference to another analog signal. QAM and ATSC signals will look like noise -- it can still impair reception, but it would need to introduce enough signal to reduce the CNR below the minimum required -- about 15 dB for ATSC, and I can't recall, but something higher for QAM. Less than that, and you won't see any effect, unlike analog interference.
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post #44 of 58 (permalink) Old 2010-11-15, 09:18 PM
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Are consumer TV's well sheilded these days ? In older days?
Depends on the brand. I've seen ingress issues for cheaper brands like Emerson. It's usually fixed by using an STB or external converter.

There are other examples of analog radio to analog cable TV interference. Years ago, when paging was popular, someone I knew lived near a paging transmitter. I can't recall the frequency, but several channels were impacted with intermittent interference.

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post #45 of 58 (permalink) Old 2010-11-16, 11:26 AM
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FCC OET did a test to determine acceptable power levels for TV Band Devices (White Space Devices)
operating in the vicinity of TVs connected to Cable (which was ignored in setting WSD power levels):
http://hraunfoss.fcc.gov/edocs_publi...C-275668A1.pdf
TV Band Devices (WSD) interfered with Cable TV reception at a level as low as 6.3 dBm EIRP (2-meters)
and 15.3 dBm EIRP (10-meters). [And I have NOT seen any follow-up tests......]
TV Band Devices (TVBD) are now allowed to operate at either 20 dBm EIRP or 16 dBm EIRP
(with reduced adjacent channel protection):
http://www.fcc.gov/Daily_Releases/Da...C-10-174A1.pdf

But in MANY homes, apts and condos, the affected range could be MUCH, MUCH greater....
These tests were done in an ALL NEW house & townhome (probably with RG-6 cable wiring, see photos).
YMMV in a typical 10+ year old house with single braid (leaky, 95% coverage) RG-58 and OLD connectors.....

Hence: THERE ARE NO WHITE SPACES ON CABLE.....

BTW: TV shielding is provided by the Tin-Can Tuner, plus metal embedded/sprayed on the plastic case.
Shielding of the Cable TV signal is provided by the Coax, which is typically RG-58 or RG-6 (newer homes).
But each F-type connector is a potential problem, depending on how well (what's left) of the braid
is secured to the outer metal and how corroded the inner wire becomes.....
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