I have the RS 20-176 scanner antenna mounted on a mast on the side of my house and I've found it to be a decent performer, I was certainly surprised at how well it performed for it's size. Definitely worth the $25.
Whatever you do stay away from the RS 20-043 discone antenna, it's a complete piece of junk. Mine's currently held together with zip ties and many parts have broken off, I don't even use it anymore. (What can I say? I was a complete noob, I didn't know about the Diamond D-130J, the Scantenna, or this forum at the time. I worked at an RS store then and was just getting into scanning for the first time.)