Originally posted by lameris
My OTA works great in analog and I've been wondering why the Digital reception is so poor.
Paul210 might be able to help out a little more, as I think he is pretty close to you and getting good results from all the Dayton, and most of the Cincinnati Digitals.
But, I'll give it a shot in case Paul's busy .... Quite a bit of this stuff applies to any receiving location in our area anyway ... It's Hard to say, there are LOTS of variables and possibilities. Off the top of my head, Follows are a few of the general issues involed, one, or a combination of factors which may be a factor(s) in you're specific circumstance:
1.)For the most part, in Dayton, the analog stations are on vastly different frequencies than their digital counterparts, and currently, the power output from the Dayton digitals aren't "really" all that equivilent to their analog counterparts. WDTN-DT 50/WKEF-DT 51 are in the Hi-UHF band, frequenices which normally especially require a lot of power to get out well, and also, frequencies on which signals are more easily attenuated by things such as walls, nearby buildings, trees/leaves/etc, in the Signal paths/etc .... WHIO-DT 41 is "sort of" "up there as well" ... The good news on this is, all the Dayton stations should be sending a good amount of signal your way, currently, per the directional radiation patterns of WHIO-DT/WRGT-DT(the others use non-directional transmitting antennas), and your quite close to the towers.
2.) For the most part, The transmitting antennas for the digital stations are a bit lower on the towers than is the case with the analog stations. Still, they are up there nice and high, but in the right "circumstances" it could make a difference. Looking on a topo map, I don't see any significant terrain differences in the area you mentioned, and since you're relatively close to the towers it should take quite a bit of terrain blockage to be a problem ... Still, if you're at the bottom of the wrong side of a steep enough hill(or other obstruction) that lies in the direction of the transmitting towers, it's possible I suppose.
3.)Multipath can especially sometimes be a problem when you're fairly close to the towers and have obstructions in, or near the signal paths -- However, If you're getting "crystal clear" reception of the Dayton analog stations(no ghosting), I'd say it is doubtful that multipath is a significant issue for you.
4.) Interference issues - Just one example, A very nearby, strong RF source, such as FM Radio Transmitter can cause interference problems, which may not be apparent on the frequencies the analog stations are using, but may be on the frequencies the digital stations are using. FCC is usually pretty good about minimizing these sorts of things though in a given area, and USUALLY, Harmonics from FM transmitters are mostly an issue on VHF High band(channels 7-13) ... However, interference from other sources can especially be an issue if you are using a preamp(or amplified antenna/etc), as these things are very broadband, and a strong signal on just about any frequency that overloads it can cause "interference" problems .... BTW, an amplified antenna or preamp for your receiving location probably isn't a great idea, as at your distance, as even strong signals from the Dayton TV stations can completely overload your preamp/tuner and spread "noise" all over other TV channels, including the ones with the Dayton stations .... Also, "Indoors" and amplified antennas usually don't mix, since Electrical noise(EMP/Impulse noise)+ other sources of RFI which can affect VHF/UHF (PC monitors/PC's/etc)indoors can be a problem ...
4a). Adjacent Channel issues/receiver selectivity issues -- Which should be less of an issue for digital than analog --- However --- Factors such as non-co located transmitting facilities, located in the same city/general area (such as WDTN-DT 50/WKEF-DT 51), and/or operating with vastly different power output could potentially make it difficult for example, for some receivers to effectively "tune in", say, a weaker signal on channel 50 due to a much, much stronger signal on channel 51. Currently WKEF-DT/WKEF-DT are operating from roughly equivelent power and antenna height, and their Full power allocations from FCC seem to be optimized to reduce this potential problem, so hopefully it won't be a problem to any great extent. This "effect" may make it difficult however from your location to tune in both WRGT-DT 30 Fox Dayton, and WXIX-DT 29, Fox Cincy.
Just wondering, but what sort of antenna are you currently using?
I think the best thing to do to improve TV/DTV reception(Generally, this should improve signal strength+reduce multipath) is to use a Directional antenna of a proven, conventional design(Yagi/Bowtie) mounted outdoors as high as is reasonably possible, away from obstructions(terrain/buildings/trees/etc) as much as possible and aimed towards the broadcasting towers.
Even when placing your antenna outdoors, it's still a very good idea to test the placement of the antenna before mounting it "permanently", as there can be "dead spots" for any given station(which can be caused by poor signal strength, multipath, or even interference problems) even outside ... Finding a "sweet spot" for your antenna which allows for good reception Is allways a good idea, whether the antenna is outdoors or indoors, although, usually finding a "sweet spot" is much more difficult indoors ... Also, While a good preamp would most likely help you with the Cincinnati stations, It most likely isn't a good idea for the Dayton stations(because of the "overload" problems mentioned above) since you're so close, and would almost need to aim right through the Dayton towers in order to aim your antenna towards Cincinnati ....
A good directional "outdoor" antenna may work indoors for you as well, but, putting your antenna indoors at the very least(in most circumstances) will reduce signal by 15-20db or so(that's a lot!), as well as increase multipath difficulties. Still, from your distance unless you have a signficant signal obstruction issue, I would think it is at least somewhat possible that a indoor antenna would work for you for the digital stations, although certian construction materials can act as especailly good signal absorbers, or reflectors, which is something you do not want.
Except for some types of insulated glass which cause signal problems, in many cases, probably the best place to put an indoor antenna would be near a Window facing the Transmitting towers(South, more or less in your case). The attic might work well also.
Just some ideas in case they help, there is plenty of excellent info on Antennas and improving reception throughout AVSforum, including earlier in this thread, as well as in the Cincinnati threads which may be useful to you.
Except for Low power analog station WWRD-LP 55, which is in the Bellbrook/Centerville area, The Dayton TV Towers are all Near Rt 4 and Gettysburg ave., on the Hill between I-75 and RT 4. I'm sure you've seen them ... They are about 8-10 Miles or so to the SSE(Almost South) of intersection of I-70 and SR48. "Generally", the Digital transmitting antennas in Dayton are around 1800~2000 feet or so Above Sea Level(approx 900~1000FT Above average terrain), which gives the Dayton Digital stations roughly the same Maximum coverage area as is the case with the analog stations ... 55-65 Miles or so, which is the case for most of the Cincinnati Stations as well. The "reachable" Cincy Towers would be Roughly SSW of your location, between about 47~53 Miles -- Of course, In a fringe area, one would generally need a fairly decent, Hi-gain outdoor antenna setup, and no significant terrain issues/etc.....
Here, I experience pretty much the opposite from what you seem to be getting. Being down in a Valley and in the "middle of the woods" as I am, It takes a antenna(with quite precise aiming) on a 35' tower in order for me to get good analog reception from most stations, free of ghosting/snow/"noise"/etc, and yet I can get most of the Cincy(27~39 miles) and Dayton Digital Stations(12-14 Miles) with a simple, $2 UHF bowtie or VHF rabbit ears(VHF antenna required for WCPO-DT 10 ABC Cincy) placed near a 2nd story window which faces the direction of the transmitting towers(2 different windows, one to the NE for Dayton, one to the S for Cincy) ... I also can induce severe ghosting(multipath) on the analog stations by rotating my quite directional(outdoor) antenna way, way off target, while at the same off target heading, good reception of the digital counterpart of the station involved is not affected.
Furthermore, The only digital station I can receive with a good enough signal via a settop antenna on the 1st floor, in the middle of the house and through 3 walls is WRGT-DT 30. I can receive no "decent"(I.e. Watchable, "fairly" ghostfree/snowfree/noisefree/etc.) analog signals from the settop indoor antenna location. From the "near the window facing the towers" locations, while I can get "watchable" quality from some of the high power analogs, It looks much, much better with the outdoor setup ... Of course, The digitals I can receive from indoors look just as good either way, although surely reception is better and probably more "dropout prone" with the outdoor antenna setup(I get no dropouts with it really, Don't know about the indoor setup as I just tried it for experiment sake, but I didn't get any for the few hours of experimentation from the stations I was receiving) .... Just a little example of how important it is to find a "sweet spot" for reception to place your antenna in ....
Probably more than you wanted to hear. Of course, experimentation is key and YMMV .... For example, while a preamp wouldn't seem to be a good idea for your location, you just never know, it might help more than it hurts .... Hope some of this helps and good luck,