What Does A Car Antenna Do I Have A Sirius Stiletto 10 & Bought A Sirius Car Antenna To Use With It. The Plug Does Not Fit. What Do I Do?

I have a Sirius Stiletto 10 & bought a Sirius Car Antenna to use with it. The plug does not fit. What do I do? - what does a car antenna do

The cap is larger than the holes in the Stiletto 10th Is there an adapter I bought at work? I have not bought the car kit or something, thought it would be cheaper and easier to just buy the antenna and connect it with the stylus. Has anyone had this problem or if someone knows what I do?