For Cumming, GA (I live in Stone Mountain), I strongly recommend the Antennas Direct 91XG (I use it myself -
http://www.antennasdirect.com/91XG_HDTV_Antenna.html ). The digital signals for the Atlanta stations are all UHF except for NBC (DTV 10). Here are the DTV assignments: WSB-DT 39; WAGA-DT 27; WXIA-DT 10; WTBS-DT 20, WPBA-DT 21; WATL-DT 25; WGCL-DT 19; WUPA-DT 43; WPXA-DT 51; WHSG-DT 44; WUVG-DT 48. When they finally turn on digital (2008), WGTV-DT will be on 12.
Once analog transmissions cease in 2009, all Atlanta DTV will be on UHF except WXIA-DT and WGTV-DT (will move to 8). I don't think you will pick-up WXIA-DT very well, that far out with the 91XG. You could try it with Channel Master 7777 pre-amp and see what happens. If it does not work, you can add a Winegard YA-6713 antenna for channels 7-13 (
http://www.winegard.com/offair/pdf/ya-6713.pdf ). The Channel Master 7777 has an option switch that offers the choice between a single VHF/UHF input, or separate VHF and UHF inputs, so you don't have to buy a band separator/combiner (default setting is single VHF/UHF input). Dow Electronics, in Duluth, probably stocks that antenna. You can also buy Winegard and Channel Master mail order from Warren Electronics (
http://www.warrenelectronics.com )
Prior to getting the 91XG, I had tried the Channel Master 4228 and Winegard 9095P antennas. There were always 1 or 2 channels that weren't reliable. With the 91XG, I have no problems.
If you want to explore this further, send me a message.