Originally Posted by Fletchy:
“I listed to Radio 5 Live and other stations in the car. Towards the end of 2015 it became impossible to pick up any of the stations to listen to. All I could hear was a loud crackling/roaring rise. A few weeks ago I found that was able to get very good reception again. Just a few days ago it deteriorated to the old crackling/roaring sound. I live in Fife in Scotland. Does anybody know what has been happening?”
Does the crackling generally rise and fall with the engine note as you go through the gears? If so it's either an earthing or suppression problem. As you live in Fife, the Westerglen transmitter is only a few miles away from you so R5L AM reception should be 100%.
The receive antenna, either external or on-glass, is connected into the radio via a screened cable that needs to be earthed both at the radio and at the antenna end. Sometimes these earth connections can oxidise with age, becoming partially or totally non-conductive and exposing the radio to pickup of the electrical pulses coming from the fuel injection system. AM radio reception and sometimes FM will gradually become more noisy or sometimes disappear suddenly.
If you can, try to access the back of the radio and reseat the antenna input plug, giving both the central pin and external barrel a wipe when you take the plug out. At the antenna end, try to expose the chassis connection and give it a clean. If it's an external antenna and the chassis hole is rusty, you can try a restorative product like Hammerite Kurust to reduce the oxide layer back to conductive Iron complexes. Halfords and others sell a pencil applicator of this stuff for less than a fiver.
On modern vehicles both these jobs are usually a PITA, so an easier alternative is that it might be poor radio suppression of the fuel injection system, and the earth connection of this not being up to scratch. Grab a manual, find the fuel injection controller, unplug the electrical connector and give it a good clean and spray with
switch cleaner or other similar product that will not damage the contacts.
Dis/re-assemble the connector a couple of times when dry and try the reception again to see whether it's been restored to its former glory...