Fixing aerial

I was hoping it would do the former, and not expecting it to do the latter.

I've found that the car already has diversity aerials for DAB (as well as AM/FM) and they are within the rear glass and already an amp connected to the aerial coax cables, so now wondering if the aerial that was mentioned might not be the most suitable, perhaps a passive roof mount instead?

My BMW E39 has a pair of aerials in the rear window and diversity reception - but that doesn't work as well as an ordinary aerial on FM or AM. Not tried it on DAB.

I guess DAB aerials have a different impedance from normal car aerials, so unless your system has a dedicated DAB output, an adaptor may not work too well.

The roof aerial I've mentioned is active. The amp for the DAB side is powered via the DAB lead - the one for AM/FM requires a 12v feed.

That's what I'm worrying about, feeding an amp into an amp sounds like a bad idea, and if it already has an amp on the existing aerials, the signal level improvement won't be as much as I'd hoped (assuming the existing amp provides reasonable gain) and how would the receiver cope with one of its diversity inputs higher than the other?

Yes, I noticed.

It's all starting to sound like a suck it and see exercise (and possibly good money after bad).

When I first got my DAB radio, I obtained a 'splitter' to feed the existing wing mounted telescopic aerial to both the inputs. It didn't work well on either DAB or FM - and AM was terrible. The set came with a separate DAB screen mounted aerial - and that didn't work too well either. But the telescopic was fine for FM and AM only.

I know the roof aerial is expensive, but it does the job excellently on all frequencies. Looks good too.

Over time we've fitted a Lot of PMR radios and most everything apart from a decent vertical roof mount has been an inefficient performer!.. FWIW...

In article , Dave Plowman (News) scribeth thus

Resonance ..Dictated in the main by aerial length.

Ideally say 226 MHz

so 300 divided by 226 is 1327 mm for Lambda (One wavelength) so quarter wave is divide by 4 is 331 mm so due to velocity factor radio waves travel slower in metal than free space say 331 x .9 is 298 mm thats the opportune aerial length for a decent roof mounted quarter wave..

Might be an idea to by a cheap mag base in Maplins for Taxi use and cut that to length whilst its on the vehicle, measure from the metal of the roof to the tip of the aerial..

Doesn't need a pre amp or anything else..

Not exactly a neat looking solution, though?

In article , Dave Plowman (News) scribeth thus

It's a test solution for the man who posted wanting to know re other aerials .This of course lets him try the performance of a 1/4 wave without drilling holes etc...

I've actually got a hole already - there is a "shark fin" on the car with GPS/GSM aerials that is superfluous to requirements.

Thanks for the encouragement ...

Well as simply what's described as a "Body mount" would be best for just DAB alone mind you that would work on FM just with reduced efficiency but certainly a lot better than on glass and other odd ideas that have cropped up over time;!..

But how well on AM? The beauty of the Panorama one is it works very well on DAB, FM, LW, MW and SW. Which is probably what you're paying for. I don't use AM often, but if and when I do I'd like it to work. ;-)

In article , Dave Plowman (News) scribeth thus

I expect it will work, 'tho how efficient it will be is questionable. Still its intended to show how a good roof mount aerial can work and will prolly suite the OP fine!..

If my DAB worked well, neither would I :-)

Need to find out where the existing aerial amp is, and how the cables are routed ...