I turned to an AM radio station this morning and noticed radio interference that sounded just like ignition noise from a gas engine. It was coming from my truck, there were no other vehicles around, and varied with my engine speed. What on a diesel would cause this "ignition" noise?

 

Charging system alternator/generator

 

Check the antenna ground. Sometimes the surface under the antenna mounting (inside the fender) area becomes a little corroded (all zinc coated parts). Pull the antenna and wire brush all the parts and reassemble. Should kill the buzz.