I just installed my Cobra 75WXST CB. I currently hace a 3' whip on it attached to the top two bolt holes for my tire carrier. I haven't tuned it yet. Will I need a longer whip it's only above the roof 8" or 9". Also is $50 a reasonable price for a SWR meter from Radioshack? Will it have instructions on how to tune my CB in the directions for the SWR meter?