In article , UnsteadyKen
scribeth thus

tony sayer wrote...

Think how much better it would be with a decent Vertical dipole;-)..

Who knows why they use these halos?,

Simple, easy to mount, and above all they get them cheap...

I think some aerial "riggers" don't have that much idea of what the do
or are doing other than "we wire this up and it usually works"

DAB is a V dipole, it is the
standard council communal installation round here for sheltered housing
and flats, consisting of a large sat dish, FM halo, DAB dipole and two
TV aerials; one pointing north for Waltham and one south for Sandy
Heath all mounted on a sturdy pole.

Receiving two different TV regions with equally strong signals confuses
a great many Freeview boxes and TV sets, plus their elderly owners.

Equipment which detects this and allows you to choose a region cope
fine, but lots end up with the whole 70 channels duplicated in the
800's

Why are they doing that? ITV 1 is much the same anywhere in that area
apart from the news I'd have thought Waltham is more your backyard
rather than the outpourings of Narwich....

In fact we did some tests on one of they and they did do better than a
coat-hanger .. which incidentally wasn't resonant;-!..

It gets those results through the use of massive amplification, whole
swathes of the VHF band are obliterated by the resulting harmonics from
the local main transmitters, (Peterborough and Geddington)



Ah!, I'm sure Bill Wright, not on this ng, could give you chapter and
verse of what they find wrong when asked in to sort these "systems"....

--
Tony Sayer

In article , UnsteadyKen
scribeth thus

tony sayer wrote...

I have seen reports by Bill Wright of Wright's aerials saying that they
very often get decent DAB signals off vertical FM dipoles in the UK.

We seem to be in a sweet spot for DAB reception round here,
especially
since the Northamptonshire service started earlier this year from the
transmitter at Geddington. The communal system also pulls in the
Leicester, Nottingham and Cambridge muxes as well as the locals, A
portable DAB radio will work on a bit of wet string and I can only
clear the memory of my DAB tuner by shorting the aerial input.
Bubbling mud, wossat?



Well!, checking out where you are on the terrain database that's some
125 Metres above ordnance datum which by most standards for that area is
bloody high!.

Its not surprising that you get good reception. There are quite a few
areas in East Anglia where 'bubbin mud is a well worn tune!...

Not everyone is so well blessed with such a decent area to live in ..
well with regards to height that is;!..

--
Tony Sayer

In message , UnsteadyKen
writes

tony sayer wrote...

Think how much better it would be with a decent Vertical dipole;-)..

Who knows why they use these halos?,

1. Halos are compact and very easy to mount on (around) a vertical mast.
They don't clutter up the space required for other aerials too much.

2. Halos have a well-defined, pretty well omnidirectional gain of around
minus 3dBd. The fact that that there a minus sign there doesn't
necessarily indicate that it doesn't perform adequately.








--
Ian

In article , Ian Jackson
wrote:
In message , UnsteadyKen
writes

tony sayer wrote...

Think how much better it would be with a decent Vertical dipole;-)..

Who knows why they use these halos?,

1. Halos are compact and very easy to mount on (around) a vertical mast.
They don't clutter up the space required for other aerials too much.

2. Halos have a well-defined, pretty well omnidirectional gain of around
minus 3dBd. The fact that that there a minus sign there doesn't
necessarily indicate that it doesn't perform adequately.

Depends on how you define 'adequately'. ;-

Yes, the user may still get enough signal to keep them happy. Although for
VHF - as people have said - a vertical dipole will probably provide more
gain.

Another way to look at the halo is to wonder where the power goes if you
try to use one as a TX antenna. This may give a clue to the inefficiency
when used for the task for which they are fitted.

I'd have on my list of reasons for why they are used:

N) Because they look to the punter like they are getting something more
impressive than a 'bit of wire' (i.e. a dipole). So the installer can
charge more for them.

and also sometimes:

N+1) So the installer doesn't have to spend any time aligning them toward a
local TX. Fit, down the ladder, present the invoice.

Slainte,

Jim

--
Please use the address on the audiomisc page if you wish to email me.
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Armstrong Audio http://www.audiomisc.co.uk/Armstrong/armstrong.html
Audio Misc http://www.audiomisc.co.uk/index.html

"Ian Jackson" wrote in
message ...
In message ,
UnsteadyKen writes

tony sayer wrote...

Think how much better it would be with a decent Vertical
dipole;-)..

Who knows why they use these halos?,

1. Halos are compact and very easy to mount on (around) a
vertical mast. They don't clutter up the space required for
other aerials too much.

2. Halos have a well-defined, pretty well omnidirectional gain
of around minus 3dBd. The fact that that there a minus sign
there doesn't necessarily indicate that it doesn't perform
adequately.








--
Ian



Come on Ian, they are crap (unless the Tx is line of sight) and
you and everyone else on here knows it.


--
Woody

harrogate three at ntlworld dot com

In message , Jim Lesurf
writes
In article , Ian Jackson
wrote:
In message , UnsteadyKen
writes

tony sayer wrote...

Think how much better it would be with a decent Vertical dipole;-)..

Who knows why they use these halos?,

1. Halos are compact and very easy to mount on (around) a vertical mast.
They don't clutter up the space required for other aerials too much.

2. Halos have a well-defined, pretty well omnidirectional gain of around
minus 3dBd. The fact that that there a minus sign there doesn't
necessarily indicate that it doesn't perform adequately.

Depends on how you define 'adequately'. ;-

'Adequately' could be that even if you put up a 'better' aerial,
reception is not noticeably - and in many cases, not measurably -
improved.

Yes, the user may still get enough signal to keep them happy. Although for
VHF - as people have said - a vertical dipole will probably provide more
gain.

'In the open' (I hesitate to say 'in free space'), a vertical halfwave
will have 3dB more gain than a horizontal halo. If you mount it 1/8 to
1/4 wave away from the mast (which you more-than-likely will) it will
also be broadly directional (sort-of cardioidal) with up to 3dB gain,
which may - or may not - be what you want. Of course, you also have to
take into account the relative field strengths of the horizontal and the
vertical signals, and if some of the required signals are predominantly
vertical, a halo is definitely not a good choice.

Another way to look at the halo is to wonder where the power goes if you
try to use one as a TX antenna. This may give a clue to the inefficiency
when used for the task for which they are fitted.

A horizontal halo used to be popular as a radio amateur aerial for 144
and 432MHz (especially for mobile work). This is because horizontal was
the norm. However, in the early 80s, the influx and immediate popularity
of ready-made FM transceivers brought a move to vertical polarization -
especially for relatively short-distance communication. These days, the
sight of a halo (whether on a vehicle or on a building) is quite a
curiosity.

I'd have on my list of reasons for why they are used:

N) Because they look to the punter like they are getting something more
impressive than a 'bit of wire' (i.e. a dipole). So the installer can
charge more for them.

A properly installed vertical dipole hardly looks like a 'bit of wire'.

and also sometimes:

N+1) So the installer doesn't have to spend any time aligning them toward a
local TX. Fit, down the ladder, present the invoice.

I doubt if installers have much difficulty in pointing a directional FM
aerial (of whatever type) roughly in the right direction (certainly less
exacting then pointing a TV aerial). Even a vertical dipole on the side
of a mast should be on the correct side. However, a halo is indeed a
100% no-brainer.
--
Ian

In message , Woody
writes
"Ian Jackson" wrote in
message ...
In message ,
UnsteadyKen writes

tony sayer wrote...

Think how much better it would be with a decent Vertical
dipole;-)..

Who knows why they use these halos?,

1. Halos are compact and very easy to mount on (around) a
vertical mast. They don't clutter up the space required for
other aerials too much.

2. Halos have a well-defined, pretty well omnidirectional gain
of around minus 3dBd. The fact that that there a minus sign
there doesn't necessarily indicate that it doesn't perform
adequately.








--
Ian



Come on Ian, they are crap (unless the Tx is line of sight) and
you and everyone else on here knows it.

It's a case of horses for courses.
Halfwave straight dipole - good?
Halfwave halo - signal 3dB less - but crap?
In most cases, you won't notice the difference.

If a halo is more than 3dB down on a dipole, either you're doing
something wrong, or the laws of physics have been changed. But if you
need something better than a halo, then you need something better than a
halo.
--
Ian

tony sayer wrote...

Why are they doing that? ITV 1 is much the same anywhere in that area
apart from the news I'd have thought Waltham is more your backyard
rather than the outpourings of Narwich....

Historical reasons I think. There are a couple of shallow valleys
running east west through the town so the slope you live on dictates
your transmitter but those on the heights; which is the majority, can
choose either, and it nearly always seems to be Anglia/BBC East

--
UnsteadyKen

tony sayer wrote...

Not everyone is so well blessed with such a decent area to live in ..
well with regards to height that is;!..

Being a new town, we're all immigrants here with no regional loyalties.
Am fay Midmar http://www.geograph.org.uk/photo/486400 and our family
moved here to get work, mains services such as gas and electricity were
much appreciated too. Though I don't think DAB reception figured high
on the list of priorities
I always look on us as being East Anglians rather than East Midlanders.


--
UnsteadyKen

In article , Ian Jackson ianREMOVET
scribeth thus
In message , UnsteadyKen
writes

tony sayer wrote...

Think how much better it would be with a decent Vertical dipole;-)..

Who knows why they use these halos?,

1. Halos are compact and very easy to mount on (around) a vertical mast.
They don't clutter up the space required for other aerials too much.

2. Halos have a well-defined, pretty well omnidirectional gain of around
minus 3dBd. The fact that that there a minus sign there doesn't
necessarily indicate that it doesn't perform adequately.








Confucius he say....

.. "All bits of metal work as aerial!.

But some bits of metal shaped differently work better"!...


--
Tony Sayer