recommendations for a vertical FM omnidirectional aerial that canbe mounted at the bottom?

Am shortly going to put up my metallic tree up against the gable end of
my new house.

I'd like recommendations for a good quality vertical omnidirectional FM
dipole that can be mounted from the bottom rather than in the middle as
it will sit on top of a pole.

I am in a dodgy FM reception area so need to get it as high as possible,
hence the reason for the mounting requirement and it will feed a 16
output multiswitch via a Televes Avant.

A matching balun for 75 ohm CT100 downlead would be appreciated as well.

Regards

Stephen

Stephen H wrote:
Am shortly going to put up my metallic tree up against the gable end of
my new house.

I'd like recommendations for a good quality vertical omnidirectional FM
dipole that can be mounted from the bottom rather than in the middle as

Vertical dipoles are always omni-directional in the horizontal plane.
However, FM (band 2) broadcast stations are horizontally polarized, so a
vertical dipole is of no use for them. I might just believe that a
single relay was vertically polarised, but you wouldn't want an
omni-directional aerial for that.

FM communications (e.g. amateur radio, and local taxis) generally is
vertically polarised, but one would normally use a colinear, with ground
plane radials, not a dipole. A dipole would require the feeder to be
taken out to the side for some distance, so that the final approach into
the near field was perpendicular to the aerial. However this is
academic for for horizontally polarised broadcast transmissions.

On 10/07/2012 07:39, David Woolley wrote:

Vertical dipoles are always omni-directional in the horizontal plane.
However, FM (band 2) broadcast stations are horizontally polarized,

WRONG !!

You're over 30 years out of date !!!

Nearly all FM radio transmissions today employ mixed or circular
polarisation.

Furthermore many local radio stations, and BBC national radio network
relay stations are vertically polarised.

Many more stations (mostly ILRs), although mixed polz, broadcast 6-8 dB
more in the vertical plane, than horizontal

There are only about three or four very small BBC relay stations that
are horizontal.

See if you can find them ?

http://www.bbc.co.uk/reception/transmitters/radio/


--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

When you say dodgy, if its multipath then you really need a beam and
probably horizontal.

brian

--
--
From the sofa of Brian Gaff -

Blind user, so no pictures please!
"Stephen H" wrote in message
...
Am shortly going to put up my metallic tree up against the gable end of my
new house.

I'd like recommendations for a good quality vertical omnidirectional FM
dipole that can be mounted from the bottom rather than in the middle as it
will sit on top of a pole.

I am in a dodgy FM reception area so need to get it as high as possible,
hence the reason for the mounting requirement and it will feed a 16 output
multiswitch via a Televes Avant.

A matching balun for 75 ohm CT100 downlead would be appreciated as well.

Regards

Stephen

I think most FM is what is known as mixed polarity, which to me means a
right mess... grin.

Brian

--
--
From the sofa of Brian Gaff -

Blind user, so no pictures please!
"David Woolley" wrote in message
...
Stephen H wrote:
Am shortly going to put up my metallic tree up against the gable end of
my new house.

I'd like recommendations for a good quality vertical omnidirectional FM
dipole that can be mounted from the bottom rather than in the middle as

Vertical dipoles are always omni-directional in the horizontal plane.
However, FM (band 2) broadcast stations are horizontally polarized, so a
vertical dipole is of no use for them. I might just believe that a single
relay was vertically polarised, but you wouldn't want an omni-directional
aerial for that.

FM communications (e.g. amateur radio, and local taxis) generally is
vertically polarised, but one would normally use a colinear, with ground
plane radials, not a dipole. A dipole would require the feeder to be
taken out to the side for some distance, so that the final approach into
the near field was perpendicular to the aerial. However this is academic
for for horizontally polarised broadcast transmissions.

Well from my tests near London, I can get much better reception on most
every legitimate station on the horizontal aerial. I feel this could well
be due to the fact that the beam width of the yagi horizontally is better or
the side rejection better than the vertical.

Brian

--
--
From the sofa of Brian Gaff -

Blind user, so no pictures please!
"Mark Carver" wrote in message
...
On 10/07/2012 07:39, David Woolley wrote:

Vertical dipoles are always omni-directional in the horizontal plane.
However, FM (band 2) broadcast stations are horizontally polarized,

WRONG !!

You're over 30 years out of date !!!

Nearly all FM radio transmissions today employ mixed or circular
polarisation.

Furthermore many local radio stations, and BBC national radio network
relay stations are vertically polarised.

Many more stations (mostly ILRs), although mixed polz, broadcast 6-8 dB
more in the vertical plane, than horizontal

There are only about three or four very small BBC relay stations that are
horizontal.

See if you can find them ?

http://www.bbc.co.uk/reception/transmitters/radio/


--
Mark
Please replace invalid and invalid with gmx and net to reply.

www.paras.org.uk

On Tue, 10 Jul 2012 07:56:36 +0100, Mark Carver
wrote:

On 10/07/2012 07:39, David Woolley wrote:

Vertical dipoles are always omni-directional in the horizontal plane.
However, FM (band 2) broadcast stations are horizontally polarized,

WRONG !!

You're over 30 years out of date !!!

Nearly all FM radio transmissions today employ mixed or circular
polarisation.

Furthermore many local radio stations, and BBC national radio network
relay stations are vertically polarised.

Many more stations (mostly ILRs), although mixed polz, broadcast 6-8 dB
more in the vertical plane, than horizontal

There are only about three or four very small BBC relay stations that
are horizontal.

See if you can find them ?

http://www.bbc.co.uk/reception/transmitters/radio/

Bearing in mind the OP's other ambitions, the simplest, cleanest
solution would be a horizontal dipole. It shouldn't be too difficult
to align this putting the nulls between any stations of interest.

In article , Brian Gaff
wrote:
Well from my tests near London, I can get much better reception on most
every legitimate station on the horizontal aerial. I feel this could
well be due to the fact that the beam width of the yagi horizontally
is better or the side rejection better than the vertical.

What tests show you get better reception on HP? absolute level or freedom
from multipath?

HP tends to have better multipath rejection, which is why the BBC chose it
in the first place. Certainly all the tower blocks in the city reflect
Wrotham rather well.

--
From KT24

Using a RISC OS computer running v5.18

In article , David Woolley
..demon.invalid scribeth thus
Stephen H wrote:
Am shortly going to put up my metallic tree up against the gable end of
my new house.

I'd like recommendations for a good quality vertical omnidirectional FM
dipole that can be mounted from the bottom rather than in the middle as

Vertical dipoles are always omni-directional in the horizontal plane.
However, FM (band 2) broadcast stations are horizontally polarized, so a
vertical dipole is of no use for them.

David.. I think you'll find the number of VHF/FM transmitters in the UK
using Horiz pol -only- can now be counted on the fingers of one hand!.

ISTR that most -all- of them are somewhere in Scotland;!.

Most all use mixed and a lot use Vertical only..

I might just believe that a
single relay was vertically polarised, but you wouldn't want an
omni-directional aerial for that.

Why not?..


FM communications (e.g. amateur radio, and local taxis) generally is
vertically polarised,

In all the years I've been involved in Mobile comms I have never known a
Horiz pol system!. Always vertical and sometimes, 'tho rarely, mixed in
buildings..

but one would normally use a colinear, with ground
plane radials, not a dipole. A dipole would require the feeder to be
taken out to the side for some distance, so that the final approach into
the near field was perpendicular to the aerial. However this is
academic for for horizontally polarised broadcast transmissions.


Umm. A collinear will be more narrow banded than a dipole. I'd use a
single folded dipole spaced around a metre away from the support mast.
This will have a certain amount of directivity but will be infinitely
better than that Horizontal Halo abortion!. If you are just after the
main BBC TX for say serious radio 3 listening I'd use a 3 or 4 element
Yagi for that....


--
Tony Sayer

In article , Brian Gaff
scribeth thus
Well from my tests near London, I can get much better reception on most
every legitimate station on the horizontal aerial. I feel this could well
be due to the fact that the beam width of the yagi horizontally is better or
the side rejection better than the vertical.

It will have better "end on" rejection.

Course these days rejection of the pirates in London is the main
deciding factor;!..


Brian


--
Tony Sayer