The electrical length of the antenna is very important to its performance. A 1/4 wave antenna is simply an antenna that is 1/4 of the wavelength of the frequency you will use it on. For UHF, which is about 450 MHz, 1/4 wave is about 6 inches long.

You can make an antenna that is much shorter than 6 inches look "electrically" like 6 inches, but there will be some reduction of performance. This reduction may not be significant if you properly mount the antenna on a metal surface.

Here is a simple formula for 1/4 wave antenna length:

234 divided by the Operating Frequency (in MHz) = length in feet

234/450=0.52 feet or 6.24 inches

I am not sure what type of antenna you are refering to CRXsi, but if you buy an antenna designed to be used at 450 MHz, and mount it as directed, it will most likely work fine for you.