DAB tuners

angusde · 10-11-2007, 12:57

Just a grumble really, but in search of an explanation....

I've been looking at replacing my existing AV receiver and been thinking about a separate Amp and Tuner. I'd like a DAB tuner, but one thing I don't understand is why they invariable seem to need 2 aerials for both DAB & FM, surely the one aerial can do both? I've a loft mounted FM aerial and want to continue to use that, can I just split that for the FM and DAB inputs? Why are they often different impedances as well?

Doesn't make much sense to me, so why are they like that?

a confused,

Angus

Nigel Goodwin · 10-11-2007, 16:33

Isn't it simply because they use different frequencies?, so they need different aerials.

You may be able to buy FM/DAB splitters?, and use your FM aerial to feed both (but it won't be optimal for DAB).

David (2) · 10-11-2007, 17:11

I went for the cheap Accoustics Solutions SP111 DAB/FM combi tuner for my hifi.

Although it does both DAB and FM, it has just a single aerial input socket.

But yes, I agree that in an ideal world you would have an aerial optimised for FM, and another DAB specific aerial - with the equipment have 2 aerial inputs. This would provide optimal results - might make a difference where FM, DAB, or both are weaker in strength than expected.

Dave

crowncd · 11-11-2007, 22:51

I have a very highly regarded Denon DAB/FM/AM tuner which has seperate antenna inputs for each type of signal. The AM antenna is internal but the DAB antenna (vertically polarised) and FM antenna (horizontally polarised) are located outside the house. I get excellent reception on all three bands. Some say DAB isn't all it's cracked up to be - I think it was initially sold as being CD quality sound - and that may be true but you have to remember some stations are DAB 'exclusive'. I do suspect that if you just had one antenna and split the signal you'd probably get decent reception on both DAB and FM.

angusde · 12-11-2007, 00:25

Thanks for the info guys.

The existing FM aerial is a horizontal omnidirectional type in the loft. We have a clear 8km line of sight to Craigkelly in one direction and 30km line of sight to Blackhill in the other.

So you reckon splitting this would be OK for FM and DAB or would a seperate vertical DAB aerial be noticably better?

Cheers,

Angus

chrisjr · 12-11-2007, 09:26

DAB is vertically polarized only. So a horizontal aerial will further compromise reception. Above and beyond the loss you will get due to using the wrong frequency band aerial in the first place.

Far better to mount a vertical DAB dipole on the roof. You also have to factor in that not all DAB transmitters are co-sited with FM transmitters. Also most local DAB services use several smaller transmitters to cover the equivalent area to a single local FM service so there may in fact be a closer local DAB transmitter to you in a direction not covered by your FM aerial.

Nigel Goodwin · 12-11-2007, 09:53

Quote:

Originally Posted by angusde

Thanks for the info guys.

The existing FM aerial is a horizontal omnidirectional type in the loft. We have a clear 8km line of sight to Craigkelly in one direction and 30km line of sight to Blackhill in the other.

So you reckon splitting this would be OK for FM and DAB or would a seperate vertical DAB aerial be noticably better?

Try splitting it first, but change your FM aerial to vertical - it doesn't need to be horizontal for FM anyway.

Paperhouse · 21-02-2008, 09:53

Quote:

Originally Posted by Nigel Goodwin

Try splitting it first, but change your FM aerial to vertical - it doesn't need to be horizontal for FM anyway.

I would suggest that an FM aerial performs better in the vertical because, not only receiving the transmitter to which it is aimed, it is better capable of receiving vertically polarised signals from others.

10-11-2007, 12:57	#1
angusde Forum Member Join Date: Nov 2005 Location: Fife Posts: 92	DAB tuners Just a grumble really, but in search of an explanation.... I've been looking at replacing my existing AV receiver and been thinking about a separate Amp and Tuner. I'd like a DAB tuner, but one thing I don't understand is why they invariable seem to need 2 aerials for both DAB & FM, surely the one aerial can do both? I've a loft mounted FM aerial and want to continue to use that, can I just split that for the FM and DAB inputs? Why are they often different impedances as well? Doesn't make much sense to me, so why are they like that? a confused, Angus

10-11-2007, 16:33	#2
Nigel Goodwin Forum Member Join Date: Apr 2006 Location: North Derbyshire Posts: 41,789	Isn't it simply because they use different frequencies?, so they need different aerials. You may be able to buy FM/DAB splitters?, and use your FM aerial to feed both (but it won't be optimal for DAB).

10-11-2007, 17:11	#3
David (2) Forum Member Join Date: Mar 2003 Location: S.West England. Posts: 18,037	I went for the cheap Accoustics Solutions SP111 DAB/FM combi tuner for my hifi. Although it does both DAB and FM, it has just a single aerial input socket. But yes, I agree that in an ideal world you would have an aerial optimised for FM, and another DAB specific aerial - with the equipment have 2 aerial inputs. This would provide optimal results - might make a difference where FM, DAB, or both are weaker in strength than expected. Dave

11-11-2007, 22:51	#4
crowncd Forum Member Join Date: Oct 2003 Location: Cannock Posts: 370	I have a very highly regarded Denon DAB/FM/AM tuner which has seperate antenna inputs for each type of signal. The AM antenna is internal but the DAB antenna (vertically polarised) and FM antenna (horizontally polarised) are located outside the house. I get excellent reception on all three bands. Some say DAB isn't all it's cracked up to be - I think it was initially sold as being CD quality sound - and that may be true but you have to remember some stations are DAB 'exclusive'. I do suspect that if you just had one antenna and split the signal you'd probably get decent reception on both DAB and FM.

12-11-2007, 00:25	#5
angusde Forum Member Join Date: Nov 2005 Location: Fife Posts: 92	Thanks for the info guys. The existing FM aerial is a horizontal omnidirectional type in the loft. We have a clear 8km line of sight to Craigkelly in one direction and 30km line of sight to Blackhill in the other. So you reckon splitting this would be OK for FM and DAB or would a seperate vertical DAB aerial be noticably better? Cheers, Angus

12-11-2007, 09:26	#6
chrisjr Forum Member Join Date: May 2004 Location: Reading Posts: 27,916	DAB is vertically polarized only. So a horizontal aerial will further compromise reception. Above and beyond the loss you will get due to using the wrong frequency band aerial in the first place. Far better to mount a vertical DAB dipole on the roof. You also have to factor in that not all DAB transmitters are co-sited with FM transmitters. Also most local DAB services use several smaller transmitters to cover the equivalent area to a single local FM service so there may in fact be a closer local DAB transmitter to you in a direction not covered by your FM aerial.

12-11-2007, 09:53	#7
Nigel Goodwin Forum Member Join Date: Apr 2006 Location: North Derbyshire Posts: 41,789	Quote: Originally Posted by angusde Thanks for the info guys. The existing FM aerial is a horizontal omnidirectional type in the loft. We have a clear 8km line of sight to Craigkelly in one direction and 30km line of sight to Blackhill in the other. So you reckon splitting this would be OK for FM and DAB or would a seperate vertical DAB aerial be noticably better? Try splitting it first, but change your FM aerial to vertical - it doesn't need to be horizontal for FM anyway.

21-02-2008, 09:53	#8
Paperhouse Forum Member Join Date: Jan 2004 Location: Crawley West Sussex Posts: 1,066	Quote: Originally Posted by Nigel Goodwin Try splitting it first, but change your FM aerial to vertical - it doesn't need to be horizontal for FM anyway. I would suggest that an FM aerial performs better in the vertical because, not only receiving the transmitter to which it is aimed, it is better capable of receiving vertically polarised signals from others.

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