Not seeing any enhanced propagation via Tropo scatter or ducting today, in fact things are pretty much as dead as they get. Just seeing all 34 of the Cincy/Dayton analog/digital stations(all within 40 Miles of my location)except WKOI-DT, and as is usual also seeing WAVE 3 Louisville/WCMH Columbus, although they are weaker than usual. Everything else is pretty much mostly "snow", as one would usually expect for this time of day where signals beyond the limit of Curvature of Earth or terrain limited directions are concerned .....
I suppose WLIO 35 Lima could potentially be a co-channel interference(CCI) issue for you concerning WLWT-DT. However, I believe you are using a good, directional antenna(CM4228 I Believe), Aimed at Cincy, and given the distance to Lima from your location I'd expect any CCI problem from them to be rare(or at least occasional and variable), although, certianly they could be adding a little "noise" off the side of the antenna.
As others have indicated, "tweaking" your antenna's position, checking connections/etc/etc would probably be a good thing to try. But to make sure these sort's of "weird problems" don't occur again, or occur mininally, I think you might have to end up doing more to improve your antenna setup if you want good, reliable reception of the Cincy DTV stations from your location. Best way to try to accomplish this I think would be to get your antenna outside.
If I recall correctly, you're in Xenia, approx. 50 miles from WLWT/WCET tower and are using a 8-bay bowtie in the attic -- If this is the case, then I think it is quite likely you are dealing with weak signals from Cincinnati, and it could be one of many, or many factors in combination which are causing your problem.
A couple of the factors especially troublesome when a weak signal is involved could be:
1.) Interference issues, of which there are many such as:
a.) Co-Channel interference - As mentioned above --
b.) Electrical interference/impulse noise - While this is more of a problem generally on VHF(Lo-VHF ch 2-6 particlarly), it can be a problem as well on UHF, and especially so if you're dealing with a weak signal. Lightning, vehicle ignition systems, Appliances in your house, powerline "slop" among other things can produce this type of interference. If you have a problem with this, you may be able to detect it as "static" or sparkles/etc. on analog signals, especially weaker ones.
2.) A change in the "Multipath" conditions(such as change when leaves are falling off trees/etc).
A couple of points:
#1) You say you're getting high "numbers" on your receiver's meter. Keep in mind, with some rare exceptions(such as S/N+AGC readings on a Hauppage Win-DTV card) Our receivers meters DO NOT measure signal strength, they can be thought of as a "signal quality" reading and measure things such as "error rate", and are implemented on the Datastream, not the RF signal itself. Therefore, a fairly weak signal just above the threshold for good DTV reception(15.3db of signal over noise(S/N)) can show high numbers on your receiver, just as an actually stronger signal would. Still, this weak signal is more susceptible to dropouts, "fluctuating meter readings", involving such issues as Interference, and multipath which your receiver's equalizer can't correct for/etc/etc.
#2) Attics(or indoors for that matter) are NOT a good place to put antennas, this is probably especially true when you are trying to pull in signals from 50 miles from the transmitter, but this applies in nearly all circumstances. Not to say that a indoor/attic antenna won't work "well enough" in any given circumstance, but in general it isn't a good idea. From indoors, putting your antenna near a window that faces the towers is often best. Good info on why attics aren't a good idea are described in the first few paragraphs at following link, and some of the issues mentioned here may very likely be things you are dealing with :http://www.kyes.com/antenna/stacking.html
Furthermore, excellent info on antennas and reception/interference issues/etc/etc can be found throughout this site, here is link to main page:http://www.kyes.com/antenna/antennadex.html
Originally posted by Jon_E_R
I guess I've seen other problems just as weird as this one.
FWIW, I can count on my fingers the number of reception related droputs I've seen in the last two years from the 13 Dayton/Cincy digital stations I receive pretty much perfectly at all times .
I was able to detirmine These few dropouts were due to either very nearby lightning strikes, or very rare, "intense" co-channel interference. It's rare for me to see even a single reception related dropout from any of these stations over a 4-6 month period of time or so. When co-channel interference has been a factor, in those instances, In addition to getting lower than normal(and fluctuating readings) from the DTV receiver's "signal quality meter", I could actually receive the interfering station quite well on a analog, non-screen blanking TV, and in fact, have often seen an analog station "through" one of the local digitals without the interfering station causing any dropout problems to the local digital station involved.
I would speculate that, in addition to being in a location with 14 digital, and 20 analog stations currently on air, all within 40 Miles of my location and most with strong signals ---- using directional, outdoor antennas aimed at the towers is the main reason why I don't really experience reception related problems here.
Anyhow, Good luck, and let us know how it goes.