Combined FM/DAB aerial
 

Does anyone make a combined FM/DAB aerial (Band II&III) for external use?
Some tuners that do both have only one aerial input.

--
*Organized Crime Is Alive And Well; It's Called Auto Insurance.

Dave Plowman London SW
To e-mail, change noise into sound.

Combined FM/DAB aerial
 

On 2007-09-17 23:43:23 +0100, "Dave Plowman (News)"
said:

Does anyone make a combined FM/DAB aerial (Band II&III) for external use?
Some tuners that do both have only one aerial input.

I looked for one a few months ago without success. Generally the DAB
antennas seem to be 1 and 4 element. I ended up with a 4 element log
periodic which seems to work well.

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal. I suppose this would mean that a combined
unit would have to have orthogonal elements.

The combining issue can be handled differently though.

When I added DAB to my distribution set up, I changed a diplexer filter
which had been combining UHF signals from two antennas (via filters)
with band 2 to a triplexer filter which has band pass ranges of Band 2,
DAB (215-230MHz) and UHF. There are three inputs.

For the outlet plates I was able to retain diplexer outputs. These
have VHF (everything below 300MHz) and UHF (everything at 470MHz and
up). Some diplexers cut off VHF at 150MHz so wouldn't work well for
DAB.


At any rate, I think that this could all be made to work with a
triplexer, wideband amp and diplexer.

Alternatively, there are VHF combiners if you just want that. Have a
look at www.teldis.co.uk Product No. SCC212/DAB/FM

Combined FM/DAB aerial
 

"Dave Plowman (News)" wrote in message
...
Does anyone make a combined FM/DAB aerial (Band II&III) for external use?
Some tuners that do both have only one aerial input.

--
*Organized Crime Is Alive And Well; It's Called Auto Insurance.

Dave Plowman London SW
To e-mail, change noise into sound.

You do not really need two aerials, one band works around 100MHz and one
200MHz, so both are harmonically related. A 1/4wave on 100 will be a
1/2wave on 200MHz. Unless you are going for 50-60miles away, local DAB
stations will be picked up on a standard dipole designed for 88-108MHz with
no problem. It's perfectly acceptable for receive purposes. Don't buy the
nasty B&Q ones as the self tapping screws allow water in to the junction
box! It's a bad design fault.
You can use a dipole for 88-108 with your TV aerial in to a
diplexer/distribution amp if you must, then split it in each room to either
TV/VHF or even TV/VHF/DAB.

Combined FM/DAB aerial
 

On 18/09/2007 00:53, Andy Hall wrote:

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal.

I thought FM used mixed or slant polarisation? Or is that only local
stations?

Combined FM/DAB aerial
 

In article ,
Andy Hall wrote:
However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal. I suppose this would mean that a combined
unit would have to have orthogonal elements.

Horizontal polarization used to be the case for main FM transmitters with
vertical for local ones IIRC, but surely most are now combined for car and
portable use? I'm also not much concerned with DXing distant transmitters.

--
*Virtual reality is its own reward *

Dave Plowman London SW
To e-mail, change noise into sound.

Combined FM/DAB aerial
 

On 2007-09-18 07:41:40 +0100, Andy Burns said:

On 18/09/2007 00:53, Andy Hall wrote:

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal.

I thought FM used mixed or slant polarisation? Or is that only local stations?

AFAIK, it's local stations

Combined FM/DAB aerial
 

In article ,
john lyon wrote:
You do not really need two aerials, one band works around 100MHz and one
200MHz, so both are harmonically related. A 1/4wave on 100 will be a
1/2wave on 200MHz. Unless you are going for 50-60miles away, local DAB
stations will be picked up on a standard dipole designed for 88-108MHz
with no problem.

This was originally my thoughts but with a 5 element FM aerial I'm
getting occasional DAB reception issues - even although in a high strength
area of South London with a direct view of both Crystal Palace and Croydon.

However, it's more complicated.

I have two aerial installations feeding different parts of the house -
mainly through history. The one on the highest part of the house with just
an FM aerial for radio works fine on DAB.

The one at the back, the one in question - which has easy access via the
roof terrace - doesn't. (The back of the house faces south so the main
building isn't in the line of sight to the transmitters)

Thinking I had simply some form of fault - although FM strengths were
excellent - I removed the FM aerial and checked it. I also replaced the
downlead, just to be sure. Tried vertical alignment instead of the
original horizontal. No - or little difference - to the DAB signal with
still the occasional 'boiling mud' issues. Of course tried the other DAB
tuner which works fine on the other aerial.

Bought a DAB aerial. DAB now fine, but FM noisy. ;-)

Thing is I don't really want a rats nest of aerials so close to the roof
terrace and fitting both current FM and DAB aerials would mean a longer
pole to clear the chimney pots on the stack while allowing reasonable
spacing. I'm wondering about cutting down the FM aerial to just the main
folded dipole as that could be fitted vertically and still look ok - but
was hoping for a neater all in one solution.

--
*Before they invented drawing boards, what did they go back to?

Dave Plowman London SW
To e-mail, change noise into sound.

Combined FM/DAB aerial
 

On Sep 18, 7:41 am, Andy Burns wrote:
On 18/09/2007 00:53, Andy Hall wrote:

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal.

I thought FM used mixed or slant polarisation? Or is that only local
stations?

I thought they changed to circular polarisation many years ago as a
result of the increased use of FM radios in cars. Car aerials pretty
much have to be vertical. That would mean that you can mount the FM
aerial at any orientation.

perhaps you coul dadd some vertical 'twigs' to the FM aerial.

Robert

Combined FM/DAB aerial
 

On 2007-09-18 08:30:35 +0100, "Dave Plowman (News)"
said:

In article ,
Andy Hall wrote:
However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal. I suppose this would mean that a combined
unit would have to have orthogonal elements.

Horizontal polarization used to be the case for main FM transmitters with
vertical for local ones IIRC, but surely most are now combined for car and
portable use? I'm also not much concerned with DXing distant transmitters.

As you were. I just found a BBC reference that main stations radiate
with mixed polarisation.

Having said that, one doesn't see vertically oriented Band 2 antennas
on houses.

Combined FM/DAB aerial
 

In article , Andy Hall scribeth thus
On 2007-09-17 23:43:23 +0100, "Dave Plowman (News)"
said:

Does anyone make a combined FM/DAB aerial (Band II&III) for external use?
Some tuners that do both have only one aerial input.

I looked for one a few months ago without success. Generally the DAB
antennas seem to be 1 and 4 element. I ended up with a 4 element log
periodic which seems to work well.

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal.

No Mr Hall, there are very few Horizontally polarised transmitters left in the
UK they are now predominantly Mixed polarisation at main sites, and Vertical
only in the case of lowered power stations..


As the OP is a great DAB fan one wonders why he's bothering with VHF FM;?

In a lot of the UK there is sufficient signal strength so that a FM band 2
dipole vertically polarised will pick up usable DAB signals...
--
Tony Sayer

Combined FM/DAB aerial
 

On 2007-09-18 09:08:33 +0100, "Dave Plowman (News)"
said:

Thing is I don't really want a rats nest of aerials so close to the roof
terrace and fitting both current FM and DAB aerials would mean a longer
pole to clear the chimney pots on the stack while allowing reasonable
spacing. I'm wondering about cutting down the FM aerial to just the main
folded dipole as that could be fitted vertically and still look ok - but
was hoping for a neater all in one solution.

That may well depend on which FM programs you want. While you might
have enough signal from anything sited at Crystal Palace or Beulah Hill
to operate an electric fire, the remaining FM stuff is from Wrotham,
which I guess is about 30km from you

Combined FM/DAB aerial
 

In article , Andy Hall
scribeth thus
On 2007-09-18 07:41:40 +0100, Andy Burns said:

On 18/09/2007 00:53, Andy Hall wrote:

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal.

I thought FM used mixed or slant polarisation? Or is that only local stations?

AFAIK, it's local stations


In the main BBC locals are mixed or rarely these days, slant. ILR with
powers up to and about 100-200 watts then to use vertical and above that
generally mixed..
--
Tony Sayer

Combined FM/DAB aerial
 

In article , Andy Hall scribeth thus
On 2007-09-18 09:08:33 +0100, "Dave Plowman (News)"
said:

Thing is I don't really want a rats nest of aerials so close to the roof
terrace and fitting both current FM and DAB aerials would mean a longer
pole to clear the chimney pots on the stack while allowing reasonable
spacing. I'm wondering about cutting down the FM aerial to just the main
folded dipole as that could be fitted vertically and still look ok - but
was hoping for a neater all in one solution.

That may well depend on which FM programs you want. While you might
have enough signal from anything sited at Crystal Palace or Beulah Hill
to operate an electric fire, the remaining FM stuff is from Wrotham,
which I guess is about 30km from you


Except that there is an FM relay at Crystal place in Dave's back yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

--
Tony Sayer

Combined FM/DAB aerial
 

On 2007-09-18 09:29:41 +0100, tony sayer said:

In article , Andy Hall scribeth thus
On 2007-09-17 23:43:23 +0100, "Dave Plowman (News)"
said:

Does anyone make a combined FM/DAB aerial (Band II&III) for external use?
Some tuners that do both have only one aerial input.

I looked for one a few months ago without success. Generally the DAB
antennas seem to be 1 and 4 element. I ended up with a 4 element log
periodic which seems to work well.

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal.

No Mr Hall, there are very few Horizontally polarised transmitters left in the
UK they are now predominantly Mixed polarisation at main sites, and Vertical
only in the case of lowered power stations..

So I've just discovered.




As the OP is a great DAB fan one wonders why he's bothering with VHF FM;?

In a lot of the UK there is sufficient signal strength so that a FM band 2
dipole vertically polarised will pick up usable DAB signals...

Even so, one doesn't see band 2 antennas deployed vertically on houses.
Perhaps that's habit by the installers?

Combined FM/DAB aerial
 

In article ,
tony sayer wrote:
As the OP is a great DAB fan one wonders why he's bothering with VHF FM;?

Just shows you chose not to understand *any* of the arguments.

With you - and others - DAB bad, FM always perfect.

I want both to be available under the best conditions - but really can't
be arsed with another DAB v FM argument especially on a sensible group
like this.

--
*7up is good for you, signed snow white*

Dave Plowman London SW
To e-mail, change noise into sound.

Combined FM/DAB aerial
 

In article ,
Andy Hall wrote:
As the OP is a great DAB fan one wonders why he's bothering with VHF
FM;?

In a lot of the UK there is sufficient signal strength so that a FM
band 2 dipole vertically polarised will pick up usable DAB signals...

Even so, one doesn't see band 2 antennas deployed vertically on houses.
Perhaps that's habit by the installers?

The vast majority you see round here are those halo thingies which are
only for local reception - so presumably should be vertical? But never are.

--
*I'm not being rude. You're just insignificant

Dave Plowman London SW
To e-mail, change noise into sound.

Combined FM/DAB aerial
 

On 2007-09-18 09:39:29 +0100, tony sayer said:

In article , Andy Hall scribeth thus
On 2007-09-18 09:08:33 +0100, "Dave Plowman (News)"
said:

Thing is I don't really want a rats nest of aerials so close to the roof
terrace and fitting both current FM and DAB aerials would mean a longer
pole to clear the chimney pots on the stack while allowing reasonable
spacing. I'm wondering about cutting down the FM aerial to just the main
folded dipole as that could be fitted vertically and still look ok - but
was hoping for a neater all in one solution.

That may well depend on which FM programs you want. While you might
have enough signal from anything sited at Crystal Palace or Beulah Hill
to operate an electric fire, the remaining FM stuff is from Wrotham,
which I guess is about 30km from you


Except that there is an FM relay at Crystal place in Dave's back yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

Presumably not as much oomph though....

Combined FM/DAB aerial
 

In article ,
Andy Hall wrote:
Except that there is an FM relay at Crystal place in Dave's back yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

Presumably not as much oomph though....

Pretty pathetic on a portable radio. Nothing like as powerful as the
genuine local stations broadcast from the same area.

--
*60-year-old, one owner - needs parts, make offer

Dave Plowman London SW
To e-mail, change noise into sound.

Combined FM/DAB aerial
 

In article , Andy Hall
scribeth thus
On 2007-09-18 09:29:41 +0100, tony sayer said:

In article , Andy Hall scribeth thus
On 2007-09-17 23:43:23 +0100, "Dave Plowman (News)"
said:

Does anyone make a combined FM/DAB aerial (Band II&III) for external use?
Some tuners that do both have only one aerial input.

I looked for one a few months ago without success. Generally the DAB
antennas seem to be 1 and 4 element. I ended up with a 4 element log
periodic which seems to work well.

However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal.

No Mr Hall, there are very few Horizontally polarised transmitters left in the
UK they are now predominantly Mixed polarisation at main sites, and Vertical
only in the case of lowered power stations..

So I've just discovered.




As the OP is a great DAB fan one wonders why he's bothering with VHF FM;?

In a lot of the UK there is sufficient signal strength so that a FM band 2
dipole vertically polarised will pick up usable DAB signals...

Even so, one doesn't see band 2 antennas deployed vertically on houses.
Perhaps that's habit by the installers?


Yes, for installers .. read cowboys;-(...
--
Tony Sayer

Combined FM/DAB aerial
 

In article , Andy Hall
scribeth thus
On 2007-09-18 09:39:29 +0100, tony sayer said:

In article , Andy Hall scribeth thus
On 2007-09-18 09:08:33 +0100, "Dave Plowman (News)"
said:

Thing is I don't really want a rats nest of aerials so close to the roof
terrace and fitting both current FM and DAB aerials would mean a longer
pole to clear the chimney pots on the stack while allowing reasonable
spacing. I'm wondering about cutting down the FM aerial to just the main
folded dipole as that could be fitted vertically and still look ok - but
was hoping for a neater all in one solution.

That may well depend on which FM programs you want. While you might
have enough signal from anything sited at Crystal Palace or Beulah Hill
to operate an electric fire, the remaining FM stuff is from Wrotham,
which I guess is about 30km from you


Except that there is an FM relay at Crystal place in Dave's back yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

Presumably not as much oomph though....


No but ..sufficient..
--
Tony Sayer

Combined FM/DAB aerial
 

In article , Dave Plowman (News)
scribeth thus
In article ,
Andy Hall wrote:
Except that there is an FM relay at Crystal place in Dave's back yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

Presumably not as much oomph though....

Pretty pathetic on a portable radio. Nothing like as powerful as the
genuine local stations broadcast from the same area.


BBC Nationals 4 kW .. Heart, Capital, Magic, LBC 2 kW...

Something rather odd there...

--
Tony Sayer

Combined FM/DAB aerial
 

On 2007-09-18 10:39:24 +0100, tony sayer said:

Yes, for installers .. read cowboys;-(...

So that's how they scale the roofs without a roof ladder - using their spurs.

Combined FM/DAB aerial
 

On 2007-09-18 10:40:11 +0100, tony sayer said:

In article , Andy Hall
scribeth thus
On 2007-09-18 09:39:29 +0100, tony sayer said:

In article , Andy Hall scribeth thus
On 2007-09-18 09:08:33 +0100, "Dave Plowman (News)"
said:

Thing is I don't really want a rats nest of aerials so close to the roof
terrace and fitting both current FM and DAB aerials would mean a longer
pole to clear the chimney pots on the stack while allowing reasonable
spacing. I'm wondering about cutting down the FM aerial to just the main
folded dipole as that could be fitted vertically and still look ok - but
was hoping for a neater all in one solution.

That may well depend on which FM programs you want. While you might
have enough signal from anything sited at Crystal Palace or Beulah Hill
to operate an electric fire, the remaining FM stuff is from Wrotham,
which I guess is about 30km from you


Except that there is an FM relay at Crystal place in Dave's back yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

Presumably not as much oomph though....


No but ..sufficient..

Presumably a local fill-in....

Combined FM/DAB aerial
 

On Tue, 18 Sep 2007 09:23:35 +0100, Andy Hall
wrote:

On 2007-09-18 08:30:35 +0100, "Dave Plowman (News)"
said:

In article ,
Andy Hall wrote:
However, AFAIK, the DAB transmissions are vertical polarisation - at
least that's the orientation of the antenna - whereas the Band 2 ones
are usually horizontal. I suppose this would mean that a combined
unit would have to have orthogonal elements.

Horizontal polarization used to be the case for main FM transmitters with
vertical for local ones IIRC, but surely most are now combined for car and
portable use? I'm also not much concerned with DXing distant transmitters.

As you were. I just found a BBC reference that main stations radiate
with mixed polarisation.

Having said that, one doesn't see vertically oriented Band 2 antennas
on houses.

That's because you don't readily notice ærials which don't have birds
perched on them. :-)

--
Frank Erskine

Combined FM/DAB aerial
 

In article ,
tony sayer wrote:
In article , Dave Plowman (News)
scribeth thus
In article ,
Andy Hall wrote:
Except that there is an FM relay at Crystal place in Dave's back yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

Presumably not as much oomph though....

Pretty pathetic on a portable radio. Nothing like as powerful as the
genuine local stations broadcast from the same area.


BBC Nationals 4 kW .. Heart, Capital, Magic, LBC 2 kW...

Something rather odd there...

Is that the power of the fill in transmitters for South London? If so they
certainly don't appear to go so far as the others above.

--
*You can't have everything, where would you put it?*

Dave Plowman London SW
To e-mail, change noise into sound.

Combined FM/DAB aerial
 

In article , Dave Plowman (News)
scribeth thus
In article ,
tony sayer wrote:
In article , Dave Plowman (News)
scribeth thus
In article ,
Andy Hall wrote:
Except that there is an FM relay at Crystal place in Dave's back
yard;!...

http://tx.mb21.co.uk/gallery/crystalpalace/index.shtml

Presumably not as much oomph though....

Pretty pathetic on a portable radio. Nothing like as powerful as the
genuine local stations broadcast from the same area.


BBC Nationals 4 kW .. Heart, Capital, Magic, LBC 2 kW...

Something rather odd there...

Is that the power of the fill in transmitters for South London? If so they
certainly don't appear to go so far as the others above.


Thats what the BBC claim...
--
Tony Sayer