Depending on how fancy you want to get, you can very easily make your own antenna with just a length of coax. Here's what I did with an old piece of ethernet (RG58) cable. (You can buy 50' of RG58 with BNC connecters for $10-15.)
- Snip the BNC connecter off one end. Leave the connecter on the other end as it will connect directly to your scanner (make sure your scanner has the appropriate antenna jack of course).
There are two ways to do the next part, the second is easier than the first:
- Measure 21 inches down from the cut end of the cable and slit a opening to expose the center strand. Pull the center strand out through the hole, so you end up with two 'ears' - 21" of shielding and 21" of core.
- Cut two 21" lengths off the end of the coax. Strip out the core of each and toss the shielding - so you end up with two 21" copper wires (or if you have 42" of copper laying around, use that instead). Strip a couple inches back off the end of the long piece of cable and separate the core from the shielding, so you have two ears, each only an inch or two long. Now attach your two loose 21" ears to the two stubs. You can solder or just twist them together securely, whatever works for you. Don't let them contact each other.
However you do it, the end result is you end up with a long length of coax, with a BNC connector on one end and two 21 inch ears on the other end. 21" is the optimum length to pick up air traffic freqs - it may not work so well if you plan to scan other freqs too. Stretch the ears in opposite directions and secure it to something, a long piece of wood, a pole, whatever. It's a good idea to put some silicone or other sealant on the bare metal of your new antenna to prevent corrosion.
I've also read of people doing this with simple electrical cord (like lamp cord), which is MUCH easier to split the ears off. You just need to figure out how to attach a BNC connector to it.
Or you can just spend the money and buy an antenna.