I have adjusted the model that uk free uses based on feedback
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 digitalaerial 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
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.