Your signal level and S/N ratio are both way off, the DTA's & digital STB's are more need a good signal level, but too much is bad also. We need to get it up at least 10db or more.
Either you have too many splitters in the house, possibly daisy chained, or your signal problem starts outside.
We need to eliminate some of the splitters, or get your home rewired to reduce the number of splitters, or add a drop amp to your home to bring up the level. It could be an outside issue, or the drop cable from the pole to the house. Weather is getting bad, and moisture & temperature will affect any poorly fitting outside F connectors.
Tell us about your wiring, how many tv's, how many outlets, if you have HSI or CDV, and how old is the wiring. The digital signals use higher frequencies than the analog signals, and there is more loss at the higher frequencies. In older homes, I find alot of old splitters that don't handle the higher frequencies, and RG59 cable has more loss at the high freqs, and the longer the coax run, the lower the signal at the outlet.
It could also be just one loose or corrorded F connector causing your signal problem, bad piece of coax or splitter. Make sure you don't have any loose F connectors on any coax, don't use twist-on or push-on F connectors. Compression F connectors are the best, don't trust any crimp on F connector just by looking at it.
OK, we need to try and find out your signal level and s/n level.
Hold down the yellow info button for 10 seconds until the diag page comes up. Use the channel down button on the remote to scroll down to the tuner status line. Press enter to select. On the tuner page it should show Power Level on one line, and Signal-to-noise on another.
Please report back those 2 numbers, so we can see if your signal level is too low.
TV is set to channel 3 and so is the black box. I'm now getting a picture, but for only for 1 or 2 mins. Then I get "service has been interrupted" and then takes about 5 mins. For the picture to come back on..Then repeats itself. I even tried to reset the box by unplugging it for a min or two. The green light is "Not Flashing"
The DTA outputs on channel 3 or 4, there is a switch on the back to select it. On the TV, selecting air or cable really doesn't make any difference, so put it on cable. The TV channel needs to be set to channel 3 or 4 to match the selection you make on the DTA switch.
Make sure the green LED on the DTA is solid green and not flashing.