Christian McArdle wrote:

Log periodics are inherently wideband and suitable for digital transmissions
that may be far from the original analogue band of the site. They tend to be
more expensive and have lower gain than a conventional Yagi, though.

Actually the gains of typical TV log-periodics are not so low as
commonly supposed. They compare well with the so-called 'wideband Yagi'
types, particularly at the LF end of the band. The trouble is that
the manufacturers only tend to quote the gain of Yagis at the HF end of
the band, where they are actually working as Yagi arrays. At the LF end
they are really corner reflectors - all the gain comes from the
arrangement of the dipole and the angled reflector and the directors are
doing very little. The gain at channel 21 is typically 3 dB (or more)
less than at channel 68. In the past the manufacturers haven't told you
that, and some may have quoted exaggerated gain figures anyway.

Take a look at the DTG/CAI document "Guidelines for the use of
Benchmarked Aerials"
http://www.dtg.org.uk/publications/b...rk_aerials.pdf.

Most of the wideband Yagi products which have been approved under this
scheme fall in Standard 2 or 3, the former requiring forward gain of 7
to 10 dBd and the latter 5 to 8 dBd. In comparison the spec. for
log-periodics (Standard 4) requires a flat 7 dBd. So in Group A, a
small Yagi (Standard 3) actually has 2 dB less gain than the log and the
quite large Standard 2 product only equals the log's performance.

For an up-to-date list of benchmarked aerials see
http://www.cai.org.uk/downloads/CAI%...g%20Scheme.pdf
The list on the DTG site seems to be out of date.

--
Andy