In my Ranger I have run several different radios and the RF noise varied depending upon the radio I was using. RCI Ranger 6900 FTB, RCI 2950 DX, Kenwood TS 50S, and most recently a Cobra 148 GTL (Malaysia '97 model).
The steps I have taken to remove the RF and engine noises....
Run 12 gauge wire power wires from battery to radio with dual fuses (battery acts as a GIANT noise filter), shield and ground power wires, replace RG-8U coax with double shielded LMR 240, install flexible magnetic material between the Wilson 5000 magnet mount and the roof for better DC coupling, replace the factory old factory platinum spark plugs with factory new platinum spark plugs, and replace factory plug wires with Taylor Spiro plug wires.
With all of these changes.... there is still a slight alternator whine and under heavy acceleration there is an ignition popping sound. Soon I will replace the factory 95A alternator with a 130A or possibly a 175A which may alleviate the remaining alternator whine.
2000 Ranger 4.0L 4dr 5 spd 4x4 w/ ORP
Modifications: 265/75R16 BFG AT KO, Detroit TruTrac l/s, K&N FIPK, 66mm BBK TB, Gibson 2.5" catback exhaust, BAMA SCT Tuner, Underdog Performance 25% underdrive pulley, James Duff Traction Bars, Taylor 8mm sparkplug wires
Future Mods: JBA Headers