The official final DTV Table Of Allotments/channel change thread - Page 10 - AVS Forum
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post #271 of 7370 Old 09-01-2007, 01:19 PM
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Sorry for the double post ...

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Originally Posted by MeowMeow View Post

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?

Personally, I don't see how.

Thinking about it, The best way I can think of how to use these things would be for the devices to use a GPS receiver to establish the device's location, and then connect to an ACCURATE database+signal prediction software to run a longely rice study for the device's specific location -- similar to it getting info similar to what you get if you run the signal prediction software here :

www.tvfool.com

And, in that case Only if signals from authorized services on any given channel are predicted to be WELL BELOW some predicted signal level for any given location should that device be allowed to transmit there .... A good "cut off" point where the things could be allowed to operate being someting in the range of less than -120dbm maybe ? Or maybe it needs to even be even a little lower than that (which would probably mean the things wouldn't be able to operate on ANY channel at all in some if not many areas) -- It needs to protect "fringe area", and BEYOND fringe area viewers IMO, not just necessarily those locations predicted to be within say, the 41dbu service contour of a UHF DTV station .... Right now, people are receiving excellent, drop out free OTA reception from BEYOND station's predicted coverage areas ....

But of course that would *still* not prevent harmful interference from occuring to "authorized services" received via enhanced signal propagation, when it occurs, nor would it prevent signals from authorized services propagating via enahanced signal propagation(such as "tropo" or "E-skip") from interfering with the unlicensed devices ... I realize the former isn't even something they are concerned, or care a whit about, but the latter, you'd think they would be ...

Then, there are also the "non-co channel" interference issues for these things and single-conversion Superhetrodyne DTV receivers addressed in various columns written by Charles Rhoades to consider ....

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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.

Not to mention what someone who gets their hands on something like that who may take great fun in finding out just what they can do with it ... (such as "hey, let's see what we can do with this thing and see if we can "mess up" the neighbor's TV reception) .... Also, what's going to keep a "Fixed" device from being moved? Is a fixed device going to detect that it's been moved and adjust accordingly?(that would seem to me to only be possible with the use of a GPS receiver in the thing) ...

Also, when interference DOES occur, exactly how are we going to be able to identify it? The "authorized" users of the spectrum(THE TV stations) can't go out to every house to detirmine why your "DTV reception is breaking up" ...

And, it's not like with analog TV where you can see interference "right on screen" ... How is the user going to know if his DTV reception is breaking up because of weak signal/fading, multipath the receiver can't correct for, OR interference from Unlicensed device or anything else? ARe they going to start to mandate Spectrum analyzer's in all sets ? LOL ....

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This whole idea is a heap of trouble waiting to happen.

Yep, I agree .... A heap of trouble for OTA TV viewers at least .... But there are plenty of smart folks(maybe not necessarily "RF smart" folks, probably) out there that think it will work Great !

Jeff
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post #272 of 7370 Old 09-01-2007, 09:41 PM
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Quote:
Originally Posted by Nitewatchman View Post

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)

Having made a read of the full PDF, my impression is that the sensing technology is based on a system implemented to broadcast in the same band as radar.

Now, my understanding is that radar doesn't need much room to avoid interference. It lacks anything as complex as even analog TV, let alone HDTV. Also, a radar sweep has to successfully return back to the source once every 12 seconds.

So, really the sensing technology has proven in one very limited situation with a fairly simple and old technology.

The next question is: do the devices really even need this band? My understanding is that the cell phone companies decided to eat 52-69 rather than any lower block of channels because the signals carried too far. Considering that the #1 use for the white space ought to be WiFi and that WiFi is notoriously unsecure, aren't we inviting even further trouble for the portable devices?

I could see an unskilled WiFi hacker having a party with white space devices and the owners pulling their hair out trying to figure out how it is happening. I can already pull in most the neighbor's wireless routers within several blocks just by sitting out on my sun porch. I had to stop letting Windows select a default because of their signals were actually stronger than mine.

I really hope someone with a half-decent tech background gets a say in this before they render this decision.
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post #273 of 7370 Old 09-02-2007, 06:37 AM
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I scanned over the FCC test report for the 'devices'. The testing was actually very nicely engineered.

I always wonder what the FCC engineering staff actually thinks about these kinds of matters. One thing is for certain. With Intel and Microsoft wanting these 'devices' to happen, they will.

--- CHAS

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post #274 of 7370 Old 09-02-2007, 10:23 AM
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The testing was actually very nicely engineered.

Yes .. For those who haven't seen that, they're here(PDF) :

Initial Evaluation of the Performance of Prototype TV-Band White Space Devices is here:

http://fjallfoss.fcc.gov/edocs_publi...C-275666A1.pdf

Direct-Pickup Interference Tests of three consumer digital Cable Television Receivers available in 2005 is here :

http://fjallfoss.fcc.gov/edocs_publi...C-275668A1.pdf

Regarding the first document above, I particularly liked that they did field tests at residences of actual DTV viewers in addition to the bench tests ... Also, although they offered the evidence as anecdotal, I also liked how they performed the OTA interference test ...

It would have been nice if they had had more prototypes to test, however ... Especially would have liked to have seen test results for devices using some of the other methods which could be used to "detect" signals from "authorized services", as well as for some fixed prototypes ...

Hopefully there will be more such tests to come, and hopefully they will be "paid attention to", so to speak ....

BTW, you'll find an interesting mix of politics and engineering in comments submitted to FCC for this proceeding, a list of which can be pulled up at ECFS search page here by inputting "04-186" (not the quotation marks) in the "Proceeding box" ... (use the view/etc. links for each entry to download the actual comments, they're in PDF format)

http://fjallfoss.fcc.gov/prod/ecfs/comsrch_v2.cgi

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

Regarding the politics involved -- In addition to what the "white spaces coalition" and groups such as "New America Foundation" want .. It seems to me it may also be about certian folks in congress who are pushing these things in hopes of wanting to do something about, or at least show that they're doing something about increasing the availabiity of hi-speed broadband access ..... Including presumably for some rural folks like me who do not have access to things such as hi-speed internet connections via cable ....

Which on the surface seems like it is probably a worthy political goal -- HOWEVER -- From a "political" standpoint, I wonder, does it make sense to encourage this pollution of the TV broadcast spectrum, given that in the future, it's allways a possibility that the broadcast spectrum, one day, *could* be repacked+more portions of it "auctioned off" ? From that perspective, who would want to bid on spectrum which is polluted with these things? [update: unless this can be a way for the microsoft+intel's to not only get their "foot in the door", but also as a means to an end -- such as eventually giving them a means to "take over the entire kingdom", so to speak -- they do seem to have a history with that sort of thing[end update] ....

Crazy as it may sound ... I think these things may actually turn out to be a *good* thing for any broadcasters out there who are, or would be solely using their "towers and transmitters" as a means to help secure cable and satellite coverage (well at least if the head-end doesn't receive the signal OTA) .... As, when/if these devices render the spectrum useless for anything else, it may be somewhat of a guarentee that the broadcasters won't ever have to "give up" their spectrum, as no one else will want it after it's polluted with these things ...

If It actually *could* be done without creating "harmful interference", then I suppose it would be a good thing all around ... Problem is, again, if they are wrong(which I think they are), once the things are out there there will be NO bringing them back ... IF it doesn't work, It will be too late for them to "change their minds" about it, and it will be the OTA viewers and broadcasters who are "stuck" with the problem, just like we+the broadcasters were "stuck" with the problem of transistioning to DTV ....

Jeff
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post #275 of 7370 Old 09-03-2007, 04:40 PM
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Does anyone have a list of post-transition channel elections that include the call sign? The list I have has the facility ID's, but not the call signs.

I have an older list that has drop down selections by State, etc. along with call signs, but that was before the final list was approved. I don't remember who made that one.

Thank you,
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post #276 of 7370 Old 09-03-2007, 05:38 PM
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The channel election TCD's with Callsigns are in Excel spreadsheets downloadable FCC site from under the respecitve dates, and at URL noted below :

1st and 2nd round tentative channel designations - "attachment" link to excel file under the 5/23/06 date at www.fcc.gov/dtv

3rd round tentative channel designations - "attachment" link to excel file found under the 8/29/06 date at www.fcc.gov/dtv

-----------

However, i suppose it would be nice to have a list of the New DTV Table of allotments with the callsigns, as there have been some(relatively few) changes since the channel election TCD's ...

The facility Id's in the Appendix B (and maybe a seperate file with the appendix G proposed changes until those are decided upon) excel files for the DTV table of allotment docuements under the 8/6/07 date at www.fcc.gov/dtv contain the DTV table of allotment info (+ a correction to the table as specified in the document listed under the 8/14/07 date) Just need to be "matched up" with the callsigns for those facility Id's like they are in the TCD files ...

Jeff
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post #277 of 7370 Old 09-05-2007, 09:02 AM
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Thank you for the info. It appears that I can simply incorporate the latest changes from the last exhibit into my existing database.

I also had a question on power levels. Is 1000kW going to remain the maximum for UHF? It is my understanding that the power levels for digital are measured differently than analog, but the effective range still seems to be lower.

Are digital power level increases after analog shut-off just a bad rumor?
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post #278 of 7370 Old 09-05-2007, 11:14 AM
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The 1 megawatt level average power is the maximum for DTV as far as I can tell. The interesting thing at UHF is that a lack of radio wave bending over the optical horizon required the high ERP on UHF in an attempt to replicate the analog VHF coverage area, which has a better ability to extend the radio horizon. The fact is that at UHF frequencies, approximately 90% of the transmit power required to reach over the optical horizon serves to expand the coverage area by only 10%. This exponential increase in power compared to the gain in coverage area become a true case of the law of diminishing return.
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post #279 of 7370 Old 09-05-2007, 11:55 AM
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Quote:
Originally Posted by KE0MI View Post

The fact is that at UHF frequencies, approximately 90% of the transmit power required to reach over the optical horizon serves to expand the coverage area by only 10%. This exponential increase in power compared to the gain in coverage area become a true case of the law of diminishing return.

The signal loss from penetrating the vegetation at UHF is also a factor that complicates reaching the radio horizon. I have always found receiving UHF to be somewhat problematic.

--- CHAS

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post #280 of 7370 Old 09-06-2007, 01:02 AM
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Do the hi-VHF digitals level-peg with the UHF digitals in terms of performance? Obviously, being at least 200 MHz lower in freq they should carry further.

However, I'm a bit worried because three of my channels are going to 8, 11 and 13 in 2009 and I'm 60mi from all three.
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post #281 of 7370 Old 09-06-2007, 01:11 PM
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It is my understanding that VHF-HI has a longer effective range than UHF and is closer to VHF-LO in range. It is also not subject to as much noise as VHF-LO.

This is probably why VHF-HI channels are the most popular in the final DTV election table, with 25% of stations choosing channels 7-13 when they represent only 14% of the post transition spectrum.
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post #282 of 7370 Old 09-06-2007, 02:09 PM
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Quote:
Originally Posted by Falcon_77 View Post

It is my understanding that VHF-HI has a longer effective range than UHF and is closer to VHF-LO in range. It is also not subject to as much noise as VHF-LO.

This is probably why VHF-HI channels are the most popular in the final DTV election table, with 25% of stations choosing channels 7-13 when they represent only 14% of the post transition spectrum.

No channel is a panacea. Each one has its own unique issues; from pulse noise, natural and/or man made; to coverage issues because of terrain, or lack there of; to operational costs and whether or not they even had an opinion to go somewhere else. Many stations in the beginning thought they did only to be turned by the FCC. Each station had to evaluate their unique situation to see what worked for them and thus the table we see now. Some choices will work out, others will not. Only time will tell which ones do and what stations may do post transition. At this point, it is all a crap shoot.

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post #283 of 7370 Old 09-06-2007, 08:27 PM
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At this point, it is all a crap shoot.

Does the FCC plan to be tolerant to a lot of reallocations after Feb 2009?

I'd imagine that since there is the first license holder rule in place -- and that seems to be religiously enforced if the first license holder decides to pick a fight -- that a lot of stations looking to take a 7-13 may have to wait to see if the first license holder vacates the space.

I guess my question then is, with the reduced ERP, will the hi-VHF channels perform as well as the UHF channels? Some of those VHF channels look like they could be powered off an old potato battery setup from fourth grade.
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post #284 of 7370 Old 09-07-2007, 04:40 AM
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Quote:
Originally Posted by MeowMeow View Post

Does the FCC plan to be tolerant to a lot of reallocations after Feb 2009?

Post transition, stations will be able to file for channel changes, but it will not be the streamline process it has been pre-transition. Stations will have to file the full packages for channel change as they have had to do in the past before the digital transition began. It could take a station several years to get a new channel assignment, first getting the table of assignments changed and then filing for the CP to build on the new channel and then the time to actually build it..

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I'd imagine that since there is the first license holder rule in place -- and that seems to be religiously enforced if the first license holder decides to pick a fight -- that a lot of stations looking to take a 7-13 may have to wait to see if the first license holder vacates the space.

If a station is already there, there is nothing any other station can do unless or until a current station changes.

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I guess my question then is, with the reduced ERP, will the hi-VHF channels perform as well as the UHF channels? Some of those VHF channels look like they could be powered off an old potato battery setup from fourth grade.

You have to remember one thing, digital coverage was based on analog coverage no matter what channel the two signals were on, based on what is already there. The coverage for the final table is based on what will fit, channel not withstanding taking into consideration what is already there. Most stations did maximize in the beginning which did help in the final table assignments.

Each band performs differently, no matter what the modulation scheme is. But yes, VHF high band should perform as well digitally as it did in analog service. I know of several stations with VHF high band digital channels and they do quite well with power levels comparable to their analog coverages. It is a fact that the VHF high band will have less stations on it post transition than they do now so with decreased noise and interference, those stations with allocations on VHF high should see an improvement of coverage, just like UHF stations will also see an improvement for the same reason, less interference. This is backed up by real time observations across the country by early adapters who had no trouble picking up low power stations in the beginning and now have trouble picking up those same stations now that they have increased powered. Remember, 1800 analog stations will cease operations Feb 17, 2009 reducing band congestion by almost 50%. That will play a huge part in reception no matter what channel the station is on.

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post #285 of 7370 Old 09-07-2007, 08:02 AM
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Fair enough. Thanks for the detailed response. I guess I will do my best to look forward to Feb 2009, as opposed to worrying.
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post #286 of 7370 Old 09-07-2007, 12:31 PM
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Quote:
Originally Posted by MeowMeow View Post

Fair enough. Thanks for the detailed response. I guess I will do my best to look forward to Feb 2009, as opposed to worrying.

When I lived in Cherry Hill NJ (near Philadelphia) during the pre-cable era I used a log periodic about 30 feet above the ground to receive New York. I had no problems receiving any of the 100 miles distant VHF channels. We had a Zenith set with vacuum tubes that provided very good pictures. I believe the signals would exceed the digital threshold today.

I have no reliable over-the-air television here in the Pocono Mountains of NE Pa so I never worried about Feb 2009. If I were building a DTV station here, I would want it to be allocated on Channel 11, 12 or 13.

--- CHAS

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post #287 of 7370 Old 09-07-2007, 08:36 PM
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Quote:
Originally Posted by HIPAR View Post

When I lived in Cherry Hill NJ (near Philadelphia) during the pre-cable era I used a log periodic about 30 feet above the ground to receive New York. I had no problems receiving any of the 100 miles distant VHF channels. We had a Zenith set with vacuum tubes that provided very good pictures. I believe the signals would exceed the digital threshold today.

But, do understand that the digital VHF channels are going to be transmitting at about a fifth the power of the analogs. That's why I am concerned.

I probably shouldn't be, as I live down in a valley, so the VHF will likely be a net benefit for me.
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post #288 of 7370 Old 09-08-2007, 08:38 AM
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Quote:
Originally Posted by MeowMeow View Post

But, do understand that the digital VHF channels are going to be transmitting at about a fifth the power of the analogs. That's why I am concerned.

Yes, I have seen references to 6 dB (or greater) advantages for the digital 8VSB system over the current NTSC waveform.

Keep in mind that detectability generally depends on received signal power strength vs the total noise power at the receiver. Granted, raw transmitter power is an important factor in the equation but other factors come into play.

The 8VSB digital system packs the power into a channel more efficiently. The redundant signal components are better removed by advanced filtering. There is no aural carrier. There is no 3.5 MHz Chroma carrier. The power is forced to be distributed uniformly within the 6 MHz wide channel.

So waveform design is always a factor when analyzing a communications signaling scheme. Let's see what actually happens in 2009.

--- CHAS

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post #289 of 7370 Old 09-09-2007, 08:07 AM
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Quote:
Originally Posted by MeowMeow View Post

But, do understand that the digital VHF channels are going to be transmitting at about a fifth the power of the analogs. That's why I am concerned.

As I understand it, DTV ERP is rated by Average Power, whereas the Analog stations are rated by Peak Power. So, it becomes a bit of an apples to oranges comparison.

Digital vs. Analog ERP
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post #290 of 7370 Old 09-09-2007, 10:27 AM
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Quote:
Originally Posted by Falcon_77 View Post

As I understand it, DTV ERP is rated by Average Power, whereas the Analog stations are rated by Peak Power. So, it becomes a bit of an apples to oranges comparison.[/url]

This is true. Digital peak is a little over 4 times the average where analog peak is a little over 2 times average.

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post #291 of 7370 Old 09-09-2007, 08:12 PM
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More detailed replies! Thanks. I need all the reassurance I can get, because I really don't want to be up on my roof in Feb 2009.
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post #292 of 7370 Old 09-18-2007, 05:40 AM
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Quote:
Originally Posted by MeowMeow View Post

...I'm a bit worried because three of my channels are going to 8, 11 and 13 in 2009 and I'm 60mi from all three.

I get KAFT-DT, VHF ch9 @ ~50mi out from the xmitter @ 100% signal strength. Xmitter power is 19kW ERP.

Biggest annoying problem, is impulse noise interference, from electrical stuff in the house and thunderstorms, which aren't always even close by. It causes very annoying dropouts. The vid dropouts can be overlooked, but when the audio drops at a very important part, it's very frustrating.

I also get KOLR-DT ch 52 perfectly right now (~70mi away). They will move from ch 52 to ch 10, post analog. Time will tell if it also has impulse noise interference.
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post #293 of 7370 Old 09-18-2007, 08:45 AM
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Originally Posted by arxaw View Post

I get KAFT-DT, VHF ch9 @ ~50mi out from the xmitter @ 100% signal strength. Xmitter power is 19kW ERP.

Biggest annoying problem, is impulse noise interference, from electrical stuff in the house and thunderstorms, which aren't always even close by. It causes very annoying dropouts. The vid dropouts can be overlooked, but when the audio drops at a very important part, it's very frustrating.

I also get KOLR-DT ch 52 perfectly right now (~70mi away). They will move from ch 52 to ch 10, post analog. Time will tell if it also has impulse noise interference.

What antenna(s) are you using? If you're in Arkansas, then your topography is fairly similar to mine (western Pennsylvania). I've never been able to get a stable signal off any of the upper UHF channels, least of all at 70 miles. Also, are you at the top of a hill?

(ADDED AFTER EDIT) I was looking at the FCC database and your KOLR has a 2000 ft tower! I wish we had anything close to that around here. Then I'd actually have line of site on something.
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post #294 of 7370 Old 09-18-2007, 12:34 PM
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Quote:
Originally Posted by MeowMeow View Post

What antenna(s) are you using? If you're in Arkansas, then your topography is fairly similar to mine (western Pennsylvania). I've never been able to get a stable signal off any of the upper UHF channels, least of all at 70 miles. Also, are you at the top of a hill?

(ADDED AFTER EDIT) I was looking at the FCC database and your KOLR has a 2000 ft tower! I wish we had anything close to that around here. Then I'd actually have line of site on something.

Yes, I'm on a hilltop @ 1405'. My antenna is also looking at trees in both directions.

IIRC, KOLR-DT's tower height, including the tower + the hill it's on is ~3000' above sea level. They share an dual antenna with KSFX-DT, and both are ~1000kW ERP. So, they are blasting the Ozarks with signal.

But I think height matters more than power with digital, because the PBS station's DT ch 23 power is only ~100kW ERP, but their tower is ~500' higher. And all 3 of these stations, plus (KYTV-DT 44) come in with consistent 100% signal strength readings. I believe KYTV-DT is also around 3500' above sea level. They all have a huge digital coverage area.

I'm using a ChannelMaster CM4228 antenna + CM7777V/U preamp. I have the back reflector screen removed off of the 4228, to make it bi-directional. That allows me to pick up 2 markets in almost opposite directions, from 45 & 70mi away, without messing with the rotor. All full power channels from both markets are 100% signal strenth. Tuner I use most is the D* HR20-700 HD DVR. The antenna is split to that box (which splits the OTA signal to 2 tuners), plus split to 3 other TVs in the house.

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post #295 of 7370 Old 09-18-2007, 09:44 PM
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Hmmm... my rig is the exact same rig, just with the reflector still intact. You look like you face a lot less foliage than I do (Pennsylvania doesn't mean Penn's Woods as a joke -- who knew?).

Over east we have a lot tighter bunching of broadcasters. Even with the back reflector on, I get tons of co-channel interference from points north and west of me.

For example, one of my two Fox affiliates transmits on Channel 29. There are two LP stations on the same channel, including on in direct line of sight of my Fox station. Then, on the backside, there is a 29 broadcasting out of Ohio.

Combine that with rough terrain and ... ugh.
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post #296 of 7370 Old 09-19-2007, 05:29 AM
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Hmmm... my rig is the exact same rig, just with the reflector still intact. You look like you face a lot less foliage than I do...

Maybe I should post a picture of all the trees. The 4228 is looking directly at tons of them in both directions. Huge pines and hardwoods - mostly oaks.

We have co-channel interference here, too, from full & LP stations. We recently fought with a LP and got them to move off a co-channel they were on w/ a full power CBS digital station. Neither the LP nor the full power station knew they were both trying to use ch 18 until they and the FCC were notified by viewers.

There are two FOX full power stations within range of me on channel 27. One analog @ 5,000kW (3000' tower), and a digital @ 200kW (~2000' tower). Guess which one wins....
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post #297 of 7370 Old 09-19-2007, 08:24 AM
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I'm going to say the digital, just because it seems contrary. On the upside, a lot of these issue ought to be disappearing in a year and a half.
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post #298 of 7370 Old 09-19-2007, 03:41 PM
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Nope. Power & tower win out. Don't even get a blip out of the digital ch., even when the screen was on the 4228.
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post #299 of 7370 Old 09-19-2007, 08:06 PM
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Nope. Power & tower win out. Don't even get a blip out of the digital ch., even when the screen was on the 4228.

I think we're all curious to see what the disappearance of analog does for our signals. If I put my address into TVFool.com's signal checker, about 3/4 of the channels are listed as having either co-channel or adjacent channel interference.
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post #300 of 7370 Old 10-24-2007, 08:33 AM
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Has anyone crunched the data to see if any major MSA's are not going to have any full power VHF stations after 2009?

The LA area, at 4 full power stations, 7, 9, 11 & 13, seems to have more than most.

What is next on the FCC's agenda? The auction of the 52-69 spectrum?
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