Why do normal roof mounted car-aerials not work with DAB in car stereos?

AnthonyUK

I have noticed several new cars sporting DAB/DAB+ radios not using a conventional roof mounted antenna but a plastic stumpy antenna bit on the back of the car-roof. Are normal roof mount angled AM/FM aerials not suitable for DAB/DAB+ car stereos? I have always thought that DAB/DAB+ car stereos would work with ANY conventional roof-mount car antenna regardless. Any ideas?;)

InsideInsurance

Coincidence?

Certainly the after market crowd sell aerials for DAB that are the old fashioned roof mounted wire.

I'd guess its more a fact that the stubby or built into the glass/ boot etc type ones are the more modern look that a wire sticking out the roof (or wing) and those offering a modern solution like DAB think the two go together better.

Have you seen any car with the old fashioned aerial that changes to the stubby type if you select DAB?

RumRat

The ones that look like a mini shark fin on the back of some models are a style statement. I think BMW's had them first, been around for a while for normal FM radios, so, not specific for DAB.
My sister had an aftermarket DAB fitted and they didn't change the aerial AFAIK.

Lomast

Although a 'normal' car antenna should work it would not be the most efficient due to the different frequencies DAB is around 220Mhz as where are the FM band is 88-108Mhz so i suspect that the stubby antennas are designed for 210-230Mhz

RumRat

Re-checked with my Sister on her upgrade. Apparently they fitted a new screen mounted aerial and just left her analogue one in place.
However, I don't believe that the shark fin aerials indicate anything. The fin just covers a small aerial that can be either Analogue or Digital dependent on the radio in the car.

Gloomendoom

I always assumed the shark fin type things were GPS aerials.

Strider590

The DAB radio in my kitchen uses an identical antenna to any regular AM/FM radio. The argument that frequency band makes a difference is bullsh*t, because AM and FM are different to each other too.

This is no different to the idea of needing special aerials for freeview digital TV, it sparked a whole industry of bullsh*ting aerial fitters who went around charging the earth when all that was really needed (in most cases) was a bit of directional tweaking of the existing analogue aerials.

wiogs

Strider590 wrote: »

The DAB radio in my kitchen uses an identical antenna to any regular AM/FM radio. The argument that frequency band makes a difference is bullsh*t, because AM and FM are different to each other too.

This is no different to the idea of needing special aerials for freeview digital TV, it sparked a whole industry of bullsh*ting aerial fitters who went around charging the earth when all that was really needed (in most cases) was a bit of directional tweaking of the existing analogue aerials.

Sadly there are still plenty of people who talk about "digital" aerials, as if such things existed.

Marketing bull !!!!!!

Strider590

wiogs wrote: »

Sadly there are still plenty of people who talk about "digital" aerials, as if such things existed.

Marketing bull !!!!!!

Well it's been argued to me that if they were not needed, then they would not be selling them. The naivety of some people is just staggering.

Norman_Castle

Shark fin aerials are likely to be more aerodynamic.

esuhl

Strider590 wrote: »

The DAB radio in my kitchen uses an identical antenna to any regular AM/FM radio. The argument that frequency band makes a difference is bullsh*t, because AM and FM are different to each other too.

An FM aerial won't receive an AM signal. As you say, the frequency bands differ too much. Often the FM aerial will be an external telescopic metal rod, whilst the AM aerial will be an internal coil around a graphite core.

In fact, even AM aerials are sometimes split in two -- one end of the coil for long wave and the other end for medium wave:
http://en.wikipedia.org/wiki/Loop_antenna#Small_loop_receiving_antennas

Recent mobile phone technology has shown how aerials made to precise fractal mathematical patterns can receive signals over a much wider bandwidth than any traditional aerial. In modern mobile phones, this allows a single aerial to receive 2G, 3G, wi-fi, bluetooth, etc. simultaneously.
http://en.wikipedia.org/wiki/Fractal_antenna