Terrible radio reception with ignition on

when you turn on the ignition, you send a feed from the unit to the rear aerial boosters, could be a problem with those boosters??

Yes I guess you need the DAB unit to tune into an fm frequency, also rds to display station info.
The other way would be to fit a combined DAB/FM aerial

hi yer Blackwood

I've come across a similar problem recently had to sort out a muppit install the guy or girl put the unit in didn't tidy or make sure the cabling was sorted and scrapped the insulation off the aerial connector on the cage as the unit went in so the connector was earthing to the car stereo wouldn't make that much of a difference but it was giving the car stereo 2 different negative voltages and using the aerial as a partial earth
and radio was great when the engine was off but as soon you turned the engine on a high pitched buzzing sound came on

If you can check the earth from the back of the stereo connector block to the negative battery connector the lower the resistance the better and the aerial cable should have a resistance of between 50 ohms and 75 ohms between conductors this will tell you that the antenna and cable is good is good I suspect that your problem may be to do with earthing

Noise problems seem to be the in thing at the moment hope this helps

After fitting a aftermarket HU I had fm issues, fortunately a friend gave me a Denison DAB unit that plugged into the usb port, so I fitted a combined fm/DAB roof aerial. I now have brilliant DAB & very good fm.