So I was tuning my Firestik II today. When I was adjusting the screw on top I tried it without putting the rubber cap back on and the SWR was really high when I held down the transmit button, high 2s almost 3!. So I put the rubber cap back on and tried transmitting again the SWR was greatly reduced, 1.2 or so. Just out of curiosity I turned the screw up some and without the cap it was really high and with the cap on it was considerably less.

Anyone know why this is? What's the rubber cap got to do with anything?

I manged to get a great SWR reading in the end by tuning to 1 and 40 so that 19 would be the lowest channel and it would sweep up from there going to higher and lower channels.