In article ,
Andy Burns wrote:
Dave Plowman (News) wrote:

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.

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?

The roof aerial I've mentioned is active. The amp for the DAB side is
powered via the DAB lead

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.

--
*The problem with the gene pool is that there is no lifeguard *

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

In article , Andy
Burns scribeth thus
tony sayer wrote:

[DAB] was intended to improve reception but it doesn't seem to improve
the original audio that much

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?

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...
--
Tony Sayer

In article , Dave Plowman (News)
scribeth thus
In article ,
Andy Burns wrote:
tony sayer wrote:

[DAB] was intended to improve reception but it doesn't seem to improve
the original audio that much

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.

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..


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.


--
Tony Sayer

In article ,
tony sayer wrote:
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?

--
*42.7% of statistics are made up. Sorry, that should read 47.2% *

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

In article , Dave Plowman (News)
scribeth thus
In article ,
tony sayer wrote:
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?


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...
--
Tony Sayer

tony sayer wrote:

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 ...

In article , Andy
Burns scribeth thus
tony sayer wrote:

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.


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;!..

Thanks for the encouragement ...

--
Tony Sayer

In article ,
tony sayer wrote:
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. ;-)

--
*It doesn't take a genius to spot a goat in a flock of sheep *

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

In article , Dave Plowman (News)
scribeth thus
In article ,
tony sayer wrote:
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. ;-)


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!..
--
Tony Sayer

Dave Plowman (News) wrote:

I don't use AM often

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

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