Originally posted by tidalwave
Out of the 15 digital channels being broadcast, ten are from the same tower and FCC states they are same power level. I receive three of the ten at high quality levels, two are very weak and sporadic, and 5 cannot even be detected by my unit.
Is it possible for it to have low sensitivity on some channel frequencies and work fine on others?
Answering your last question first, it's probable that your antenna is more sensitive to certain signals, although the 4228 has a pretty flat response curve. Keep in mind that your antenna becomes more directional at higher frequencies, so if you're slightly off-axis, stations like WCCO and KMSP will be fine while KSTC might give you problems and KSTP definitely would.
Stations I'd expect you to have trouble receiving: KTCI (50kw), WFTC (circularly polarized, also very low placement of transmitting antenna), KMWB (20kw, directionaly biased away from you.) All the others should be good-to-great.
The 811 is a world-class dog in performance - it has the worst reception attributes of any digital STB out there. Search the hardware forum for scads of horror stories about how poorly this STB works. If you can get your hands on a different tuner to try it out, you may be able to eliminate the antenna setup as the problem.
Check your analog reception of 23, 29 and 45. Are the images ghost-free and relatively snow-free? If you see even the hint of a ghost, that will probably knock the 811 into a frenzy. You could also try removing the preamp (both indoor and outdoor units) to see if reception improves. Sometimes the preamp boosts multipath that would otherwise be invisible to the receiver.