I've found AntennaWeb to be very conservative in their estimates. I generally do not recommend it and instead refer people to TVFool.com and then have people with good knowledge of antennas look at the plot and look at the specific location and then recommend something based on that.
AntennaWeb likes to tell me I only receive 2 channels. TVFool says I receive 9. I actually receive 6 stations reliably, and there are good excuses for the remaining three (low power until June, low-VHF signal sucks, and poor signal quality from the transmitter) which always show me signal even if they don't decode.
I generally do not point people at AntennaWeb for that reason. The
FCC database is generally pretty accurate (though it likes to keep outdated records active), their formula is just very conservative.
- Trip
