/diy/ - Do It Yourself

>>225105
>I have a 4' Firestik II as my antenna, and I heard somewhere I was supposed to tune it or something

The SWR (Standing Wave Ratio) of an antenna must be tuned for the resonant frequency. An ideal SWR is 1:1, although anything from 1:1.1 to 1:1.5 is excellent. Up to a 2.0 is fine, but anything over 2.5, I would start worrying. ANY quality built antenna should be able to give you a tuned SWR of less than 2.0. If it's over 2.5, you've likely chosen a bad location to mount the antenna and are having a lot of reflected energy, or you have a poor RF ground plane.

To tune your SWR, you need an SWR meter like this one: >http://www.frys.com/product/3415093

To change the resonant frequency of the antenna, you shorten or lengthen the antenna. To raise the resonant frequency from say... 27.185 mhz, to 27.355 mhz, you would SHORTEN the antenna. To lower the resonant frequency frmo 27.355 mhz to 27.015 mhz, you would LENGTHEN the antenna. As you can guess, it's kinda hard to lengthen antennas, as you usually change the resonant frequency by cutting 1/8" pieces of antenna off. Luckily though, I believe the Firestik II has an adjustable metal post under the tip's cap that you can raise or lower?

Magnet mount antennas such as the Wilson W1000 has a stainless whip that is attached to the bottom via an allen bolt that pinches it in place. You can loosen the allen bolt, and slide the whip up and down to tune it.