Cobra CB Antenna to 10 meter antenna

[lobo8000]

I have a cheap Cobra CB magnet mount antenna that I would like use for 10 meters. It's about 21 inches long with a four inch rubber thingy 1/4 of the way up. My question is: should I trim it at all for 10 meter use? As well, what is that rubber thingy for? Thanks.

 

[jrplmil]

If you have a way check the SWR and see what you have. If it is over 2 to 1 then trim it. only about 1/10th of an inch at a time. When you talk about the rubber thingy I think you are talking about the load. All that is is a coil of wire to help shorten the overall length of the antenna. On the cb band a 1/4 wave antenna with no coil would be 102 inches long. I hope that helps you some.