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.
Originally Posted by Larry Kenney
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.
Prohibited on same channel: 0-170 mi
Prohibited on adjacent channel: 14.29-68.35 mi
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.
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 ....