If you are in a DTV OTA
area here's a cheap, simple alternative to hiring a professional with signal detection equipment. You get what you pay for, so I recommend the professional for best results!
You'll need a small portable TV and antenna
(rabbit ears if you have to, but a proper antenna
in medium to deep fringe areas), a stepladder, a hammer and some pegs, a compass, some duct tape, and maybe an assistant to help carry stuff and keep notes. If you already have a DTV tuner, that's even better because you can log the results of its strength meter as you test. In my case I use a 13" portable colour tv with a Channel Master 4228 antenna
on a 3m mast.
Methodically walk the TV around your
yard in 1 x 1 metre grid steps (you can even do this on your
roof, but be careful!) using the compass to point the antenna
at the area where the DTV stations are, repeatedly scanning all the VHF and UHF analog channels each time you move to the next grid. Repeat repeat repeat... and don't make assumptions that you won't need to scan all the channels each and every time. Half a meter can make a difference, so go through them all each time.
If you find that some of the analog stations might be snowy that's okay because that means signal strength is the only problem. If ghosting is occurring, you have a more serious problem called "multipathing", which is always to be avoided since an equivalent DTV signal would therefore probably not be viable for reception at that specific location. DTV is hit particularly hard by multipathing.
Generally if you find one or two "sweet spots" in which you are getting a good number of analog stations in relatively good signal condition with minimal ghosting, hammer a locator peg into the grass or mark a locator on your
roof with duct tape (which you can write on with a ball point pen), write down your
results in a log book, and try to find out how altitude affects the results by taking the gear
up the stepladder. Of course stepladders and roofs are generally a bad combination...
so please don't try that. Usually the higher the antenna
the better, but that's not always true in areas with big trees and building overhangs, sundeck roofs, etc. so don't be surprised if there is no performance gain.
When you're back at your
computer compare your
written results with the other results from your
area here in the stickied threads to see how good you're doing. If all looks good you can set up an antenna
on a mast there and start pulling in the DTV stations.
Note that you get what you paid for, so if you're not satisfied with the results, its time to get that professional to come over and run proper tests.