I have been having the same problem since the switchover. I am using Vista Media Center with an HDHomerun tuner. I have rescanned the channels numerous times, and even attempted manual entries for channels 6.1, 6.2, 6.3, and 6.4... It's too bad they can't go back to the UHF channel that was working fine before the switchover, instead of clinging to their VHF low frequency...
I even tried calling WRGB engineering, and the gentleman I spoke with made a comment that channel 6 (maybe because it is on VHF low) is not antenna friendly. So I tried at least 3 different antennas, including rabbit ears, with no luck. My primary is a DB8 antenna, from Antennas Direct (http://www.antennasdirect.com/DB8_HD_Antenna.html). I even tried a different tuner, thinking that maybe the HDHomerun was having trouble picking up the frequency, but even that produced nothing.
And it isn't even that the signal is so weak that it doesn't work well... There is absolutely no signal, whatsoever.
It sounds like there are 2 issues here; poor signal and wrong frequency.
For wrong frequency, you have to manually add it in.
for Vista w/o tvpack, find the astcchannels.xml file and just delete it. It's hidden so you have to search for hidden files. Then go to tasks/tv/guide/add missing channels/add dtv channel and add it back in on the proper frequency. It should be something like logical ch 6.1 on physical ch 6. Then re-download the guide. If it still doesnt work, you did it wrong or its poor signal.
For Vista w/tvpack and Win7 users, just go to tasks/tv/guide/add missing channels/add dtv channel and add it in on the correct channel as above. You should have 2 ch 6's now, one should work, the other shouldnt. If it doesnt work, you did it wrong or its poor signal. If it does work, you need to copy the gauide data from the bad channel to the new channel. Go to tasks/tv/guide/edit channels and select the channel you just added. Then select edit listings, find & select the bad channel and when it says merge or copy, you want to copy the listings from the bad channel to the new channel.
For poor signal, many stations that elected to revert to their old vhf channels are regretting making that decision. It's turning out that the models used to calculate transmit power output over estimated the coverage of a digital VHF signal. Also, they underestimated how well a VHF signal penetrates buildings in urban areas. Thus, far out there is no reception because the alotted power is too low. Close in, there is no reception because people are using indoor antennas and VHF isnt penetrating buildings very well.
Here in Chicago, ABC moved from a gangbuster signal on UHF to a just awful signal on VHF. CBS went from a really really awful signal on low VHF to a mediocre signal at high VHF. ABC just petitioned the FCC to move back to UHF and CBS just petitioned for a UHF low power relay station.
From the looks of things, you are on the right track. RF channel 6 is in the low VHF band. The way the FCC defines and breaks down the frequencies means that channel 6 ranges from 82MHz to 88MHz. There is a break or separation between the low and high bands of VHF with channel 7 ranging from 174MHz to 180MHz. The gap in frequencies between channel 6 and 7 is because those ranges have been assigned to non-TV broadcasting. For instance, FM radio ranges from 87.8 to 108MHz. The reason I point out the gap is because the gap makes it much less likely that a high-VHF antenna will have good low-VHF properties.
There are very few TV broadcasters in the US that still use the low VHF band. The DB8 is a UHF and high-VHF antenna. While this site doesn't specifically test the DB8, this Channel Master 4228 is a similar design. You'll note in the chart at the very bottom of the page, the antenna's gain in the low VHF band is particularly poor. The same site discusses the DB8 here, but doesn't talk about its VHF capabilities. In order to get channel 6, you may have to try an antenna that specifically has elements for low VHF.