In article , Jim Lesurf jcgl@st-
and.demon.co.uk writes
In article , Dave Plowman (News)
wrote:
In article , Paul Hopkins
wrote:
Last August, Hi-world did a piece on aerials, a copy may be available
from their subscriptions department. They suggested a Antiferance 3
element VHF aerial and an All-rounder dipole ( the round element) it
all depends on transmitters.

Those round things may have made sense if you needed an omni in the days
when VHF transmissions were only horizontally polarized, but these days
all are vertical or mixed for mobile reception, so a vertical dipole is
better.

Maybe I am out of date. However I had thought that the VHF/FM transmissions
were 45deg slant or circular. Hence either vertical or horizontal might do
in a good area. The advantage of vertical is that it gives 'omni' in the
horizontal plane.


Yes it does for reception. For quite some while now most all BBC main
systems have radiated Mixed i.e. Vertical and Horizontal components.

A few of the smaller commercial stations use vertical only, and IIRC
somewhere in the country there is a station that still is Horizontal
only!.

Mike Browns excellent Transmitter gallery site has a bit on this...

http://tx.mb21.co.uk/gallery/wrotham/mixedpol.asp


and more about various types of transmission system aerials.

http://tx.mb21.co.uk/features/recognition/vhf-fm.asp
--
Tony Sayer

Bancom Communications Ltd U.K. Tel+44 1223 566577 Fax+44 1223 566588

P.O. Box 280, Cambridge, England, CB2 2DY E-Mail