I used to work at a two way radio (motorola) dealer. One of the bits of information I picked up was that the antenna length needs to match up to the frequency. I contacted Shure about this and after a couple of go arounds, they provided me with an online calculator for figuring the exact length the antenna should be extended. BTW most wireless antennas are 1/4 wave. Go here and fill in your frequency and it will tell you the exact length your antenna needs to be. http://www.csgnetwork.com/freqwavelengthcalc.html It turns out my antenna only extends to 15" but optimal length should be 15.4" per the calculator. The difference is negligible and in the real world will work just fine, but I would think a difference of a few inches might be a problem. This site also has some other real cool calculators, scroll down to the bottom.