Welcome to Dayton thread..
Generally speaking, if you can get decent reception of analog stations(via your attic antenna - not via locals from direcTV dish), reasonably clear of ghosting+snow or "signs of interference", then chances are very good you'll get good digital(HD) reception as well. This is especially true in our area, where digital stations are running from nice, high transmitting antenna heights, on the same towers as the analogs, and for the most part with a good amount of power. From what I and many others have seen, getting good DTV reception is actually easier than getting good analog reception, but of course, YMMV as there are many variables involved ...
Yes, there are great advantages to using a directional antenna ... A directional antenna will provide much more signal gain than a "omni-directional" or multidirectional antenna in the direction it is aimed, while rejecting signals(and rejecting interference+mulltipath - which creates ghosting on analog signals+can cause digital reception problems too - more info in previous posts here) in the directions it isn't aimed towards.
A directional antenna, mounted outdoors, away from any nearby obstructions and as high as is reasonably possible(and aimed at the towers - Dayton+Cincinnati towers would be in different directions of course from your location, so if you wanted to receive stations from both cities, the best thing to do is use either seperate directional antennas on seperate feedlines(with an A/B switch near receiver to select antennas), or a single antenna w/rotor so you can turn the antenna) Is usually the way to go to get the best reception possible ... Now, this doesn't mean you can't get good reception from indoors, just that its the "way to go" if you want best results ... Many have had excellent results with reception from indoors, and it may work out well for you too, although you might need to do a little work at it ... See previous posts and links to outside sources on antenna/reception info for more details/information on indoor reception ...
Also, Most stations in our area broadcast on UHF presently, but WCPO-DT Cincinnati is on VHF 10 - So, you'll likely need VHF/UHF antenna for best reception ... Once analog shut off occurs, many stations will move their digital stations from UHF back to their current VHF analog channel assignment.
Probably the biggest "problem issue" for good reception in our area is if you live in a low spot, with terrain(Hills) blocking the signal path. Especially problematical can be a high hill very near your location.
Also, you might find the AVSforum Cincinnati thread ( http://www.avsforum.com/avs-vb/showt...0&pagenumber=1
) useful+informative for info on the Cincinnati Stations/etc.
Now -- some questions to help us, so we can try to help you more, and hopefully some comments that may be of use to you :
Are you sure you are getting the analogs via the antenna in your attic, and not from the dish?(direcTV sends local SD stations via sat, but they don't send HD from stations via the satellite) ?
If you are getting the local analogs via antenna, are you seeing much ghosting/snow? If not, you should be receiving the digital stations as well. If you are seeing ghosting/snow on the analog stations, which channels are they on? Do you have any stations showing up with a x.1, or x-1 designation on your screen? (such as say, 12-1 for CBS WKRC-DT - Digital/HD - Cincinnati). You should see other numbers besides x.1 from some stations as well, such as 48.2, 48.3, 48.4, 48.5 from WCET-DT, PBS Cincinnati ... Keep in mind, Digital Stations don't send HD all the time -- Only when HD is "available" .. the rest of the time, they send 4x3 SD, just as is on the analog stations, but oftentimes "upconverted" to HD resolutions (It usually won't look a whole lot different in many cases)
What is the Make/Model of Antenna which DirecTV installed in your attic?
What is the Make/Model of the receiver you are using for DirecTV HD/OTA HD reception? Some receivers have certian necessary "settings" that have to be correct before you'll be able to scan for+see the digital stations -- for example, some receivers need a zip code(s) from the area the stations you want to receive so the APG guide info can be "coordinated" for those stations ... Just about all receivers require you to have the Antenna input set for "off-air" reception, instead of "cable" ... If it is set to "cable", then VHF analog stations (ch 2-13) and MAYBE WCPO-DT Digital(ch 10, remaps to 9-x) Cincinnati .. will be all it will be able to "find", as it won't scan UHF channels for signals unless it is set to "off air" or "antenna"/etc ...