Well things have taken a turn, after installing the dudu7. In my original post above it was before installation I was still using an Eonon Q30pro head unit (topway TS18 based) and the signal was fantastic, could and often did, drive round the whole county(West Yorkshire UK) with barely any dropouts. Since putting in the dudu7 the signal is rubbish. Its 5 miles to my mums and thats down a hill, through a town centre along a road with high buildings either side, then up a valley with plenty of roadside trees, on the old unit full signal all the way, on the dudu its unlistenable most of the way.
Same dongle, same antenna. So whats different:
Reverse camera wires now run up same A pillar...Possible interference but unlikely as only powered when in reverse and set that way in dudu settings...I had no reverse camera on old unit
GPS antenna wire runs alongside dab antenna for about 100mm...possible interference, on old unit the cable was routed straight up and away from dab cable
I now have a DVR dash cam...very possible source of interference, though cables don't run together
Dab dongle plugged into new USB cables(USB2) on dudu which is the six pin, on old unit was plugged into the 4 pin one...its possible the new USB cables are not well shielded
I have a usb flas drive in USB1 and on old unit both DAB and flash drive were never plugged in together as only had 2 usb not 3 like the dudu and the 6 pin on old unit had a 4g modem always plugged in as no built in 4g and wifi on Eonon was rubbish.
I have an adas DVR in USB3 but that is a good 100 mm away from other 2 ports
I have a cheap usb c fast charge cable plugged into the usbc port on the back......very possibly badly sheilded as very cheap aliexpress thing
The dudu is Qled screen(I believe so anyway??) so could be a cause of interference.
So conclusion is that something on that list is causing inteference in the signal, it must be so maybe the OP is having similar.
My starting point will be to remove the dudu's 4 pin single usb and replace with the one from my old unit and remove the usbc fastcharge cable(which I won't really need anyway) and possibly fit ferrite cores on the DVR cable