MrM

With my wife away with work I had a chance to have a go at fitting an external Hirschmann DAB aerial I bought a little while back from dabonwheels. I bought a DAB Alpine headunit a couple of years ago and have been using it with an internal aerial on the windscreen. I've read comments slating the internal aerial, my experience hasn't been too bad. I live in south west London, reception is generally good, however it does tend to be affected when I charge my phone in the car. On to that in a sec. My wife's BMW with DAB very rarely drops signal wherever we go, so clearly my little internal aerial is lacking, hence why I wanted to upgrade.

Electrical interference seems common place with DAB, my wife's car is also affected too. When one of our phones is plugged into certain usb cigarette adapters, the moment the phone is attached the signal drops, unplug it and like magic the signal comes back. Some cigarette adapters seem to cause this problem, others not so, or to a lesser extent. I need to spend more time experimenting but my internal aerial is much more badly affected than my wife's car with the factory external shark fin aerial. I found online that "ferrite cores" can be used to reduce noise from electrical wired devices. They are the conical sections you sometimes see on camera or satnav usb chargers; I've always wondered what they were. Before I replaced the internal DAB aerial and the OEM FM aerial, I attached ferrite cores to my charging cable both at source and next to the phone. There was a small improvement, but it was clear as day that on parts of the M25 I could get DAB signal if my phone wasn't charging, but signal would vanish as soon as a connection was made, so the ferrite core wasn't the magical solution I hope it might be.

So on to the fitting of the new external DAB aerial. The only reference I could find by searching was Nick Graves' effort. I expected a few hiccups along the way and that's what I got. Removing the old aerial was more straight forward than expected. I put masking tape all around the old aerial base to save any potential paintwork damage. I initially started to remove the old aerial bezel using a flat tipped screwdriver covered in electrical tape and a hammer which loosened it up. I then used a pair of thin nosed pliers covered in electrical tape to unscrew the bezel. It finally gave up its resistance and came free. A Screw keeps the base of the assembly attached to the body of the car, accessed from inside the boot and then the whole unit comes free. The hole in the wing is surprisingly large and oval in shape so I had to make some minor modifications to ensure the new aerial base fitted correctly. I ran the DAB cable through the boot beside the spare wheel, then down the side of the passenger door under the kick plate and under the dash. I have a small fuse box in the cubby hole behind the passenger seat which powers my heated seats, dashcam and iphone charging cable; so I added a cable to power the aerial using a 1A fuse. The bit I was fearing most was removing the head unit face plate. This is the third time I've done it so I've got the knack, the first two times were a little more hair raising and I've come close to snapping the clips at the bottom of the fascia on the previous occasion.

For those that haven't done it or struggled I will share my thoughts and experience. In my opinion removal of the gear knob and gear surround/arm rest panel is essential. In doing so you can pull the radio door fascia off by pulling horizontally, rather than upwards at a slight angle which is what happens if you leave the armrest panel in place. This should release the bottom clips. A trim removal tool slid vertically beside the left and right sides of the headunit and prised outwards allows the clips on the side to be released and then lastly slide the tool in above the heater vents which allows you to prize the top part out. This was the easiest it's been for me yet. DAB aerials swapped over and to my relief I still received a signal. Furthermore, it was a very good signal and I can report even on weaker stations that I struggled with before come over loud and clear and more importantly even when my phone is charging. Needless to say I'm very happy with the result and an afternoon well spent.

The only negative is the FM attachment of the new aerial is a little odd and I haven't managed to connect it as yet, but then I haven't listened to FM for a long time so not too concerned.

Thoroughly enjoying my a well deserved beer tonight.

Nick Graves

Interesting to read your observations.

If you are having probs with electromagnetic radiation, would not using the wire powering the original twig keep the loop separate from your own supply and therefore help reduce the issue?

I've forgotten where I grounded the new twig (inner wing area), but moving yours might delta the resistance on the ground loop and reduce (or increase!) interference.

Bloody Tesla...

MrM

Thanks for your reply Nick. The internal aerial is powered by the headunit. I have taken a new power feed for the new one, so not sure if that has helped or not, there's quite a few variables. With regards to the interference I had, it was present irrespective of where I sourced power, whether that be from the socket between the seats or from a separately wired DIY adapter, it was the same effect.

Will report back once I've driven around a bit in the usual spots where it used to drop. Seems I need to buy an adapter to fit the FM cables. Typical!

Interestingly there is no ground for my new aerial? Only 3 wires protrude from the base; FM, DAB and power. The washer underneath that tightens the whole assembly to the body has some "teeth" on it, so not sure if that acts as a ground?

Nottm_S2

To add more mud to the water in my BM i use a pure thingy which came with a winda twig

Works fine, never drops, this reports a full signal pretty much all the time (has the same strength indicator as your mobile)

In the S i have a pioneer unit with a similar twig, drops in a couple of low signal areas on my old commute

Maybe the S is electronically noisey

MrM

Interesting, thanks for the info. Signal dropping I understand, it's the presumed electromagnetic interference that has me intrigued and that's more of an issue. Without changing a phone the internal aerial is ok. When charging it becomes very inreliable with "weaker" DAB broadcasts.

Does your Pure system broadcast DAB to a tuned FM station? I had my old Aston retrofitted with a DAB unit which did this. Was an ok solution but never as good as a bone fide DAB input imo.

Nick Graves

Since I JB-welded a body washer into the oval hole, I added an earth from the aerial base to the body.

The NSX has a converter on its FM bumper-car pole and the decoder unit feeds an FM signal into the back of the HU via FM. Works very well.

Nottm_S2

No, the BM has an aux in. They have an uber complex stereo which is all integrated into the iDrive FRED so hard to swap for a DAB hu

it's this



and i can plug my phone through it too so works a treat in dragging the car into the 21st century. ahem

MrM

I thought I should add an update comment. I've not done many miles but where I have been DAB and FM reception has been great. Big improvement over the internal aerial. Furthermore and somewhat bizarrely, even when I unscrew the antenna from the base to fit the cover on, DAB reception is still great in my garage. Go figure!