strange beeping over the speakers in a factory 99 cherokee

[jbjbjbj]

sorry if this has been asked already but i can't find an answer in the search field.

i've just bought my first jeep (a UK '99 Grand Cherokee Orvis 2.5 diesel manual) with the factory cassette/radio. The radio has started cutting out and going to a regular beeping every now and again (over the speakers). it goes away when you turn it off and back on but very quickly returns. i can't find any radio feature in the manual that matches it and i can't find anything online.

any help is greatly appreciated!

 

[carnuck]

Static build up from bad antenna ground or the gov't is tracking you

 

[dnr421]

Mine sounds like an alarm coming through the speakers

 

[MattMayTJ]

On my 97 TJ the speakers used to make a noise that would almost match the hum of the engine just a little more higher pitched but then I bought a new head unit and speakers and never heard it again