[Elasticband]

Is it possible in any way to use my FM roof aerial to receive DAB broadcasts or will it require a dedicated aerial?

Perhaps it would be possible to split my High Gain(Freeview) TV aerial and use that, or would it reduce the signal strength and so effect the TV?

Any thoughts appreciated.....

[television2004]

Quote:

Originally Posted by Elasticband

Is it possible in any way to use my FM roof aerial to receive DAB broadcasts or will it require a dedicated aerial?

Perhaps it would be possible to split my High Gain(Freeview) TV aerial and use that, or would it reduce the signal strength and so effect the TV?

Any thoughts appreciated.....

The first problem is the polarisation. All Band II aerials (FM) are horizontally polarised. Dab transmissions are vertical The second is the frequency VHF band II is 88-108 Mhz which is half that of DAB which is Band III 175 -225 Mhz.
An old ITV band III aerial which was usually vertically polarised would work a lot better.

[flying haggis]

Quote:

Originally Posted by television2004

The first problem is the polarisation. All Band II aerials (FM) are horizontally polarised. Dab transmissions are vertical The second is the frequency VHF band II is 88-108 Mhz which is half that of DAB which is Band III 175 -225 Mhz.
An old ITV band III aerial which was usually vertically polarised would work a lot better.

whilst i agree that an FM aerial is not ideal for DAB surely any aerial is usually better than no aerial.
try connecting the screen of the FM aerial cable to the input of the Dab radio as the screen of the cable is effectively a long straight upright aerial

[David (2)]

Quote:

Originally Posted by Elasticband

Is it possible in any way to use my FM roof aerial to receive DAB broadcasts or will it require a dedicated aerial?

Perhaps it would be possible to split my High Gain(Freeview) TV aerial and use that, or would it reduce the signal strength and so effect the TV?

Any thoughts appreciated.....

Depends on your fm aerial. If you have a horizontal fm aerial, it wont work very well at all on dab since all dab signals are vertical. However, if your fm aerial is vertical (my one is a single fm dipole - vertical), it will work quite well, provided the aerial is pointing towards a dab transmitter - or it's a single vertical dipole fm aerial, in which case it picks of signals from all around.

I dont recommend using your tv aerial. For a start the aerial is the wrong design altogether, and many tv aerials are horizontal, while dab is vertical. You also need to use a vhf/uhf bootster/splitter box, so you can get the vhf (inc dab) from the aerial without dropping the freeview reception.

Dave

[Elasticband]

Quote:

Originally Posted by David (2)

Depends on your fm aerial. If you have a horizontal fm aerial, it wont work very well at all on dab since all dab signals are vertical. However, if your fm aerial is vertical (my one is a single fm dipole - vertical), it will work quite well, provided the aerial is pointing towards a dab transmitter - or it's a single vertical dipole fm aerial, in which case it picks of signals from all around.

I dont recommend using your tv aerial. For a start the aerial is the wrong design altogether, and many tv aerials are horizontal, while dab is vertical. You also need to use a vhf/uhf bootster/splitter box, so you can get the vhf (inc dab) from the aerial without dropping the freeview reception.

Dave

Thanks for that....

Looks like I'm going to have to cough up some money...

[David (2)]

Quote:

Originally Posted by Elasticband

Thanks for that....

Looks like I'm going to have to cough up some money...

Its not that bad. A simply "omnidirectional" single dipole aerial should only cost around £10. Dont spend extra on a 3 element models as they only pick up signals from 1 transmitter. If there is more than one dab transmitter in your area, you want to be able to get stations from all of them - hence the single dipole design. Very simple to put together - must be vertical alignment for dab signals. Can be put in the loft if the signal strength is good.

Dave

[davey_do_little]

It depends on the strength of the signal. I use an old home made FM aerial for DAB in the loft (vertically mounted) and it is fine. If you already have an aeriel of any type, why not just try it before going to any expense?

[tight fart]

They are both broadcast in both Horizontal and vertical (If they weren't your car aerial wouldn't work) But you do need a different aerial. If you are in a strong signal area get a singal bar or omni, if not look at the Antiference 4 bar or Triax range. ( an omni should cost less than £10, the larger no more than £20)

[digispec]

Quote:

Originally Posted by tight fart

They are both broadcast in both Horizontal and vertical (If they weren't your car aerial wouldn't work)

Oh, I didn't realise this, I thought all UK DAB transmissions were vertically polarized, and worked because the car aerial has a large vertical component at all times.

[David (2)]

Please supply official text saying UK DAB signals are also horizontal.........


BBC fact sheet
Snipit
Digital radio
Because digital radio uses higher frequencies
230 MHz as opposed to 87.5-108
specific aerial to listen to the service.
The best aerial to use for digital radio omnidirectional
(or all round) aerial. However
may be better if you are in an area where
It must be mounted with its rods vertical.
installer will know which way to point
reliable results.
If you need a directional aerial check
of fibreglass rather than aluminium
interference problems). Make sure
and all connections are secure.

Link
http://www.bbc.co.uk/reception/factsheets/index.shtml
*then click the "radio aerials and good reception" item (text version).

Dave

[digispec]

Thanks for that, David (2), The fact is that DAB signals in the UK are only vertically polarised, as I originally thought.

[David (2)]

Quote:

Originally Posted by digispec

Thanks for that, David (2), The fact is that DAB signals in the UK are only vertically polarised, as I originally thought.

I stress time and time again to people I know who have DAB radios, that in 99.9% of cases the aerial should be "fully extended and vertical". Quite a few of them can't resist the temptation to put the darn thing at a 45º angle then ask me why their "classic fm on dab" sounds like boiling water (borderline signal). Put the aerial back to full length and vertical and its works fine again.

and whatever you do, dont bother hooking up a loop or "halo" aerial to a DAB radio. They are rubbish at DAB reception - possibly due to the fact they are not designed for it

Dave

[bobcar]

Quote:

Originally Posted by David (2)

I stress time and time again to people I know who have DAB radios, that in 99.9% of cases the aerial should be "fully extended and vertical". Quite a few of them can't resist the temptation to put the darn thing at a 45º angle then ask me why their "classic fm on dab" sounds like boiling water (borderline signal). Put the aerial back to full length and vertical and its works fine again.
Dave

It depends on where the aerial is installed, if it's the integral whip aerial then they are usually inside a room with reflections etc. For the channels I listen to the best result both in sound quality and signal level is with the aerial at aproximately 45 degrees. This is in a room with lots of computers so is untypical but my advice would be to move the aerial around until best reception is received.

Obviously I'm talking about an indoor aerial here not a rooftop one which should almost always be vertical.

[David (2)]

You could be part of the 0.1% then. I use a Pure Elan DX20 at work (pull up telescopic aerial), and we have 6 computers, plus printers and scanners all in the same room, plus there's lots of other computer based equipment and heavy equipment through the walls, plus we are at ground level and have a metal roof! But the DAB still works best with the aerial vertical - the signal meter drops back if you tilt the aerial. In addition to that, I recently set up a new DAB-FM combi at home for the hifi (wire aerial), and again it worked best with the aerial wire going straight up - infact the effect was more marked, as when I held the cord at an angle I lost some stations altogether.

Dave