DAB reception suddenly poor

The aerial system is a single aerial with a "masthead" RF amplifier. It is fed with a twin cable. The main cable is the FM cable and that also carries the 12volts for the amplifier. The DAB cable is the second part of the twin. It carries no DC voltage but joins to the same masthead amplifier which suggests to me there is an duplexer in there.

As the FM side is working it sounds as if that side of the cable is working and that pre-amp is working. Either the DAB side of the pre-amp has died or the connection under the aerial has failed.

DrRobin wrote:

Soeley, I see in another thread you replaced your DAB antenna by removing the headlining, any hints and tips how to remove the headlining and gain access?

Robin

From memory, undo the rear grab handles, remove the rear interior light and the (2?) push clips along the rear edge of the head lining. There are some more push clips in the centre. You can just about get access to the antenna that way, if you want more room, remove the front passenger grab handle, pull the door seals down to clear the head lining and tease the head lining out from behind the B-pillar trim.

I think that's about it.

see docs

Thanks Martin, Soeley,

I took the headlining down in that corner, quick and easy with both of your instructions.

I tested it again on DAB, FS -27 to -29 with the occasional value of -51dBm, this suggests a bd connection.

I checked and cleaned the plug, the signal stayed the same, but now when I remove the antenna it goes down to -30 to -32dBm so at least it is doing something.

I removed the plug and the signal fell to -75dBm, but the radio still received the station with some drop outs. The minimum level for reception of DAB is about -86dBm, so a signal of -25 to -30dBm is very good.

I next set about removing the antenna, I didn’t check the torque on the bolt but it was definitely lower than 7Nm.

The little bracket was stuck in place and took some shifting, but once off but once off there was very little paint removed for the earth prongs to get a good contact.

I removed a little paint and applied some copper tape (pictures to follow) and once back together the signal improved to -23dBm, with no departures to -50.

It looks like it might have been a bad earth, possibly when moving and the antenna swinging about.

Photos of the better earth

 

This is copper tape with a strap to the airbag fixing, good earth point.

Then with the antenna fitted
 

I have just been for a little drive, although not the standard test route and no DAB drop outs at all, so hopefully it’s fixed.

Thanks for all of the help.

Robin

I think the antenna clamp, is supposed to pierce the paint with it having 4 spikes on it? But the copper tape looks a better solution.