In article , UnsteadyKen
scribeth thus

Gordon MacPherson wrote...

The DAB has an F type connector. I would like to
be able to use both FM and DAB from the single cable.

1. If it is possible, what would be the most effective way of setting this
up?

It depends on your existing signal level, if it is good then you could
use a simple passive splitter but you may need to use a signal booster
to compensate for the loss incurred in the splitter.

I'm in a similar situation, in that our communal aerial system provides
a single combined (very good) FM/DAB feed.
I tried various ways of getting this to to my FM & DAB tuners
including a couple of passive splitters and they were fine for DAB but
degraded the FM signal too much compared to a direct connection.

In the end I got one of these 1 in 2 out amplifiers
http://www.philex.com/catalogue/prod...d=116&cat=1069
which works well for both DAB and FM. It has a variable gain control
which allows you to fine tune things.

Here are the results of using that on the end of a much derided FM
halo.
http://goo.gl/maps/sF9Yh


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

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


That design, if you can call it that, was used for some IBA transmit
aerials waay back before they devised better mixed polarisation ones but
it has got a relative loss compared to the straight half wave dipole..

As regards matching alluded to elsewhere its worth remembering that a
simple half wave dipole has a typical impedance at resonance of 73 ohms
but when folded this rises to close on 300 hence the need for a
transformer to wind that down to a more useful value and also to an
unbalanced cable as 300 ohm.. does anyone use that anymore in the UK I
rather suspect not.

Sadly most all FM aerials made in the UK dispense with any attempt at a
balun device apart from some Triax ones. Antiference use another odd
arrangement.

If you NEC model a half wave fm dipole whilst the SWR does go high at
DAB frequencies the gain oddly enough improves around the DAB sector.
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.

Whilst on the humble Halo and V and H polarisation it is true to say
that most all main stations and higher power relays do use Mixed
polarisation but some relays and most all community stations use
Vertical only hence another reason for the implementation of a vertical
dipole RX aerial..

--
Tony Sayer

tony sayer wrote...

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

Who knows why they use these halos?, 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

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)



--
UnsteadyKen

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

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

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 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

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?


--
UnsteadyKen

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