The Natural Philosopher wrote:

The day a balun turns one pile of aluminium scrap intyo a 'digital aerial'
is the day I send my degree in electronics back..

No one said it did. But DTT (DVB-T) as currently transmitted in the UK
is somewhat more demanding of receiving antenna performance than
analogue, particularly if you want (a) an aerial that bears some
relation to the assumptions used by the transmitter planners in regard
to gain, directional properties and cross-polar discrimination, and (b)
freedom from impulsive interference.

The term "digital aerial" has come in to use to mean an antenna that
meets a certain set of criteria that will distinguish it from your "pile
of aluminium scrap."

Go read
http://www.dtg.org.uk/publications/b...rk_aerials.pdf.

A balun is necessary, but not sufficient. The main purpose of a balun
is to prevent coupling between common-mode feeder current (which of
course on a coaxial cable will flow on the outer surface of the outer
conductor) and the wanted (differential-mode) signal path. In the DTT
reception context it reduces coupling between impulsive electrical
interference picked up on the outer of the outer of the coax (acting as
a 'long-wire' aerial) and the wanted signal path. It is most important
to use properly screened outlet plates and receiver flyleads, for
exactly the same reason.

HTH
--
Andy