I'm yet another Laguna owner with poor reception but hopefully I have some useful answers.
1) It seems well established that the rear heater causes interference with the radio reception. I have found that the rear heater is turned on automatically when you start the car but is not shown as being on on the heater display. I'm not sure if the heater switches on every time or only if the outside temperature is below a certain point. Either way switch the rear heater on and off to definitely turn the rear heater off to stop the interference.
2) Bad earthing point! Below are the instructions for a Laguna II estate where the ariel is on the side window but I'm sure other cars will be of similar designs.
There is an ariel amplifier in the boot close to where the ariel wire joins into the screen. On the Laguna estate you need to undo one screw and then it's a bit of brute force to unclip the plastic trim.
The blue box is the ariel amplifier which needs a 12v supply to operate. To test if your amplifier works, remove the red crimp and you should hear the radio reception become worse. If there is no difference in reception, check that you have 12v between this red wire and earth.
If the amplifier seems OK disconnect the ariel cable by pushing the yellow collar towards the blue unit and the aerial cable will just pop out. The black wire just unclips from the glass. Remove the module by unscrewing the 10mm nut.
The metal mounting tab of the amplifier acts as both the 0v for the power supply and the ariel ground plane. Get a wire brush and go crazy! Make sure BOTH SIDES of this metal tab go from a dull colour to nice and shiny. Give the same wire brush treatment to the mounting bolt and around the mounting bolt on the car bodywork. Show no mercy with the wire brush and get everything as shiny as possible, I cannot emphasise how important this is.
Once everything is clean, fitting is the reverse of removal.
I should imagine on hatchbacks that there is an earthing wire between the hatchback boot lid and the main car bodywork. If there is remove the wire at both ends and give the crimps and the mounting studs a good old fashioned wire brushing to.
It***8217;s also worth gently
squeezing the black clip with a pair of pliers to ensure a tight fit when it clips back onto the window stud.
I have done this with my car and seen a HUGE improvement. Local stations are no longer scratchy and the radio picks up other stations it previously missed when auto tuning. Is still have problems with the rear heater causing interference but this is easily solved by turning the rear heater off!
If you have a go at this, please post your results and let me know how you got on.