Hey guys....any random length of wire will give you great additional distance. It seems the longer...the better. 39 inches is the approximate length on a 72 mHz reciever antenna, but that length is cut to resonate with the actual frquency for optimum performance. For this little scanner...it doesn't seem to matter what length you use. I tried a six inch piece of wire, but found that the range was only marginally improved. A three foot piece gave much greater range...but not as convenient for carrying in your shirt pocket. I plugged in an old 6 foot stereo cord that was just lying around and it worked perfectly too. The jack on the unit accepts a standard mini earphone plug, available at places like Radio Shack, and connecting an antenna wire to the center (tip) is the way to go. Any kind of wire and any size of wire works just fine. Stranded wire is nicer to use because it is flexible. Solid conductor wire (like telephone wire) is stiffer, and it will break after being bent repeatedly. You need not try to over engineer this thing. The antenna is really a very simple device....an old wire coathanger would work...anything that is a conductor of electricity works just fine. If you have an old headphone set lying around...and if the plug fits the scanner...just plug it in...it'll do the trick very well too. For use at the club impound...tack up a long length or wire right on the impound and just leave it there with it's little mini plug on the end. Then when you want to monitor the whole field, just plug in the antenna and leave the checker right there at the impound. For use directly on the flight line, you really dont need any external antenna,....assuming all the other pilots have their antennas extended!
Have fun.
Jim