ND antenna delete

Hi -

Have decided that I need to loose the huge whip antenna on my new ND - it messes up the looks of the car IMHO. The rubber ducky conversions are a slight improvement I think, but they're not for me.

So first port of call is to get an alternative antenna that's out of sight and works well. I listen to DAB 99% of the time so that's my priority. In the past I have made DAB only coax aerials for aftermarket radios that have a separate DAB antenna input, but the ND radio has just the one antenna to do the lot, and it has some fancy electronic gubbins in the base which I assume does the converting between AM, FM and DAB. The sat nav is not affected by the rear antenna, it must have it's own antenna elsewhere on the car.

So I've removed the outer bits (unscrew main ant, then remove circular nut with circlip pliers) - then removed the RHS boot liner and removed the 10mm nut that holds the base of the antenna. I have placed a piece of duct tape over the inside of the hole as a temp cover.

So my homemade DIY antenna is made from a piece of thin 75 ohm coax cable (thinner than the standard TV stuff) , I have stripped the outer cover and braiding from 1m of cable, so you have 1m of inner conductor with it's plastic insulation on one end of the coax. I found a short piece of plastic tube in my pile of bits & bobs, and have coiled the free end of the coax around it as in the photos, it's just taped up at the moment but I will order some glue lined heatshrink sleeve to make a more professional looking job of it.

It's fastened to the inner edge of the rear wheelarch plastic liner, as shown in the photo. I drilled some 4mm holes in the edge of the cover so I could attach the antenna with small cable ties.

I found a spare hole in the "boot" floor that was taped over at the factory, have run the coax up through there towards the original antenna base. At the other end of the coax I have fixed the inner conductor wire to the antenna with a short M5 stainless cap head bolt and a couple of stainless washers, and cut back the outer insulation to expose some of the coax braiding, which I have cable tied up tight against the outer body of the antenna base, to ground it.

I have rotated the antenna base to clear the body and re-fixed it with the original nut but will try to find a way to secure the top end as well for a long term solution.

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So does it work ? - Yes - very well

My first experiment didn't go so well though - I tried 1.5m of wire, that was brilliant picking up FM but lousy at getting DAB which is what I mainly want. So looking up some numbers, the BBC puts out it's DAB signal at a wavelength of 1.382 meters, which would make a 3/4 wave antenna 99.6cm long. (near enough 1M) - so I cut it down to 1m, Excellent DAB and FM reception. Even picks up DAB in my garage with the door closed, which the stock antenna struggled with so I'm pretty chuffed so far. Been out for a drive with it and no loss of reception at any point.

So it needs a neaten up with some heatshrink sleeve and a better attachment for the original ant base but that's the first part of the job sorted.

Next bit is to cover the hole in the body.

It would be nice if there were oval plastic plugs available in body colours but I can't find any. A round blanking grommet won't sit right or seal properly.

So my plan (and next weekend's project) is to make an aluminium oval cover plate a little larger than the hole, anodise it black and fit with a stainless countersunk screw in the centre. Will keep you posted....

Dave.