poor / no radio reception Disco

i have poor/ no radio reception in my 1998 disco. The aerial is built into the rear side window and i have connected the blue aerial power feed to my head unit but still no reception.
Is this a common issue???

i also have really poor radio signal in my disco

poor Aerial ground - very common - remove aerial and clean ground plane if its the usual "mount on the body" type - built in ones, you obviously cant remove - still worth checking ground points tho for corrosion.

Remove radio and check that all leads are in correctly, then it is probably down to an earthing problem, put it on MW and put on the indicators if they interfere with reception it is an earth, this can be BODGED by connecting a slim earth wire to the back of the unit and finding a good earth on the dash, lights etc and there you go, Alternatively get a cheap aerial from any car spares plug that in and stick it in the engine bay by winscreen wipers fully extended not ideal but it will work. Keep us updated

Have you checked the amplifer, located behind the trim panel surrounding the R/H alpine light for it's power supply and wiring comnnections, coax etc.