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Thread: Adjacent local digital TV stations any interference?

  1. #1
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    Default Adjacent local digital TV stations any interference?

    On the Northern Oregon Coast we have several OTA translators. 17 (5kw ERP), 21 (1.86 KW ERP), 23 (5 KW ERP), 26 (5 KW ERP), and 34 (.563 KW ERP). Well there is a new CP for channel 22 with 15 KW ERP. At the same site with the others. Will there be any interference with 21 and 23? In the analog days, that would not be allowed. I am sure some of you must have adjacent locals to each other in the cities. Strange they would apply for 22 with other channels open. The CP is to move from 51 to 22. That is needed with the FCC rules now. The station (KHPN) is not on the air. Tested at one time on 51, but never came on. But it looks like that are looking tio come on in the near future. Thanks.

  2. #2
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    With full-power stations the FCC permits adjacent channels if the transmitters are at or near the same site. (I want to say 4km but would have to look it up)

    The analog rules were based on the UHF receivers available in 1952. Clearly, receivers are FAR better today and can easily handle adjacent channels if the signals aren't too different in strength.
    Doug Smith W9WI
    Pleasant View, TN EM66
    http://www.w9wi.com

  3. #3
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    I live in Akron, Ohio where I have channels adjacent to each other with no problems. I have a repeater on RF 24 which is 11 kW right next to blowtorch WVPX RF 23 @ 1000 kW. They're both on the same tower., and there's no issues Also, WEAO RF 50 is adjacent to WDLI RF 49 (both full-power). Those towers are about 2 miles apart. There is minor interference caused to WEAO by WDLI when I aim right at the WDLI tower, but it's not that bad. I'm right in the middle of all these towers.

    As for DX, WDLI RF 49 wipes out any good DX on RF 48. The WDLI tower is less than 1 mile from my home.
    Andrew

    My TV and FM DX Photos from Akron, Ohio...
    https://www.flickr.com/photos/133179000@N04/albums

  4. #4
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    Adding to what Doug said, the current rules allow DTV stations on adjacent channels to exist with towers close in proximity (I think it's more like 7 miles... not sure of exact number) otherwise full-power stations have to be separated by something like 60 miles. Where I live local WTBY-27 is close-spaced to WNBC-28 at only about 50 miles.... and makes WNBC unreceivable here without a tropo boost. (The rest of the full-power NYC signals come in fine). The best scenario is to have adjacent channel stations on the same tower. From a spectrum efficiency standpoint, it is ideal to have all stations in a market one channel apart, and I think we'll see a more of a move in that direction with the current repacking. Right now my locals are on 22,24,27,32 & 48 (w/ a 42 analog)... that type of allocation is going to change.
    Chris - Poughkeepsie, NY
    DTV DXer since April 2009
    DTV DX screenshots at: http://www.flickr.com/photos/dtvdxer/sets
    DTV DX Videos at: http://www.youtube.com/user/dtvdxer

  5. #5
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    Thanks for the feedback. The two translator sites are within a mile from each other I believe. I wonder if 21 (KPTV) and 23 (KOPB) have been notified of the new adjacent? I may call the CE at KPTV tomorrow and ask.

  6. #6
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    I looked into the specifics on this one; the permit for KHPN-LD would be on a tower whose distance from K21DE-D and K23GK-D would be measured in feet. The worst case difference in signal level looks to be about 10 dB, give or take, at least over the flatter parts of the coverage area. This is well within the capability of a digital TV receiver to handle, with the minimum protection by the FCC being 26 or 28 dB and the performance guidelines from ATSC being 33 dB.

    EDIT: Looking at it on Google Satellite View ( https://www.rabbitears.info/location...+Mountain+(WA) click on "Satellite" at the top right of the map ), it actually looks like there's just one tower there with the different stations having filed slightly different coordinates for it. It looks like 26 and 34 share an antenna, 17 and 23 share an antenna, and 28 and (soon) 22 will share an antenna, with 21 on its own antenna somewhat lower on the tower. Is 28 on the air?

    - Trip
    Last edited by Trip; 02-03-2017 at 08:27 AM. Reason: Changed link because I changed the location name based on a post below..
    Come visit RabbitEars for all your digital TV subchannel informational needs.

    Comments are my own and not that of the FCC (my employer) or anyone else.

  7. #7
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    I had a chance to look up the regulation.

    For new channel allotments (if the FCC ever permits that to happen..) adjacent UHF channels must be either within 24km (15 miles) or more than 110km (about 65 miles). The figures are slightly less for VHF -- 20km in Zone I (the Northeast as far as the Mississippi River), 23km elsewhere.
    Doug Smith W9WI
    Pleasant View, TN EM66
    http://www.w9wi.com

  8. #8
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    Here in Minneapolis we have 3 such examples

    K16HY EWTN 16 & WUMN Univision 17...same spot (IDS Building)...both 15kw LP stations
    WUCW CW (22) and KTCI PBS (23)...same spot. Telefarm in Shoreview (maybe 7-8 miles from downtown Minneapolis)

    Then the big one...5 in a row
    31 WDMI-LD Daystar (IDS) 15kw
    32 WCCO CBS (Telefarm) 1000kw
    33 K33LN 3ABN (IDS) 15kw
    34 KTCA PBS (Telefarm) 662kw
    35 KSTP ABC (Telefarm) 755kw

    I'm pretty sure the full powers are happy that the auction didnt make the top station stop at 29

  9. #9
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    We've got two 4-in-a-rows (or more) in Phoenix...

    KNXV 15
    KPHE LD 16
    KPHO 17
    K18JL 18

    K38IZ-D 38
    KTAZ 39
    KEJR LD 40
    KPDF CD 41
    KVPA LD 42
    Este programa es público, ajeno a cualquier partido político. Queda prohibido el uso para fines distintos a los establecidos en el programa.

    Read the Mexico Beat | Download Mexican FM Station Coordinates v2 | View my HD Radio in Mexico map

  10. #10
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    Quote Originally Posted by Trip View Post
    I looked into the specifics on this one; the permit for KHPN-LD would be on a tower whose distance from K21DE-D and K23GK-D would be measured in feet. The worst case difference in signal level looks to be about 10 dB, give or take, at least over the flatter parts of the coverage area. This is well within the capability of a digital TV receiver to handle, with the minimum protection by the FCC being 26 or 28 dB and the performance guidelines from ATSC being 33 dB.

    EDIT: Looking at it on Google Satellite View ( https://www.rabbitears.info/location...inook+%28WA%29 click on "Satellite" at the top right of the map ), it actually looks like there's just one tower there with the different stations having filed slightly different coordinates for it. It looks like 26 and 34 share an antenna, 17 and 23 share an antenna, and 28 and (soon) 22 will share an antenna, with 21 on its own antenna somewhat lower on the tower. Is 28 on the air?

    - Trip
    Thanks for the feedback. So 28 and 22 will be on the same stick. Yes, the sites are close together. 28 tested in analog back in the 90s.But they did not stay on for long. 22 (was 51), had a poor tx site (2 KW ERP), but apparently they wanted better coverage. Megler Mt (SW WA), has the height to cover SW WA/NW OR. Here is the list of what we have:

    2.1 KATU ABC HD (26) (5 KW ERP)
    2.2 METV HD
    2.3 The Comet SD
    2.4 Coming

    6.1 KOIN CBS HD (34) (576w ERP)
    6.2 Get TV SD
    6.3 Decades SD

    8.1 KGW NBC HD (17) (4.5 KW ERP)
    8.2 Justice TV SD
    8.3 Estrella SD

    10.1 KOPB PBS HD (23) (5.7 KW ERP)
    10.2 OPB+ PBS HD
    10.3 PBS Kids SD
    10.4 NPR Radio (3 streams) SD

    12.1 KPTV FOX HD (21) (1.86 KW ERP)
    12.2 COZI SD
    12.3 Laff SD

    We have the CP's for 22 & 28, plus others for 15, 36, & 38. We also have a couple old ones that are listed as on the air, but they were never on (4 & 5). One has an app for ch 24. EWTN tested in analog on 42 years ago, but the outfit let the CP run out. They tried an app for 43, but I presume none of those will sign on, not above channel 30. The 5 translators we do have are owned and operated by the Portland TV stations. But considering our area of coverage is probably 35K, even having 16 OTA channels is great!

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