Why does the UK Free Freeview predictions differ from other sites?
 Brian Butterworth published on UK Free TV
Brian Butterworth published on UK Free TV  I have adjusted the model that uk free uses based on feedback 
and testing.
The predictions often do not match the "official" value 
because feedback from ukfree.tv users have indicated the differences. 
The original ONdigital boxes required a much stronger signal. 
The switch of four multiplexes to 16QAM mode, and the 
introduction of the Class I digital aerial brings better coverage. 
Also, I found that many people in "poor coverage" aerials are 
happy to get a new aerial to get Freeview because in these 
areas Freeview pictures are noticeably better than analogue 
signal provides.
What I also found was that where it was necessary to change 
the aerial from pointing at a local analogue only transmitter 
to a remote Freeview transmitter, people would do this rather 
than wait another six years.
I also found that in some coastal areas it was common for 
people to use very long poles to get a good signal.
The original ONdigital predictions were before the 
introduction of 16QAM mode for four of the multiplexes (1, B, 
C and D) and the increase in power at some transmitters, so 
you expect some slight changes to the database.
The predictions by ukfree.tv take into account the 
line-of-sight to the transmitter, the power of the signals and 
the aerial height required to get a signal.