The ATAS is designed to be a mobile antenna so you don't need full sized radials for 40 meters. Think about the average car. It's about 6X20 feet. If you are going to use it as a base antenna you should elevate it as much as possible and use half a dozen or more 20 foot radials. It will tune just like it should but there's a catch. A mobile antenna is not very efficient so don't expect great results.
Good luck with it.
As an aside, for a lot less than you will spend on the ATAS 120, you can get a set of Hamsticks for the car, a tuner, and build a wire antenna for your fixed station. Make a dipole any length that you have space for, the longer the better. Feed it with 300 or 450 ohm ladder line and buy yourself an inexpensive tuner that will tune balanced line. This will work about a hundred times better than the ATAS for fixed operation and depending on the length should load up on most bands. Even an end fed wire will work much better than the ATAS in a fixed station application.
I know the ATAS is sexy but it is a compromise antenna to put it mildly and the hamsticks will probably out perform it. You just have to get out of the car to change bands.
Last edited by KA4DPO; 10-01-2008 at 09:47 PM.
If it weren't for Philo T. Farnsworth we'd still be eating frozen radio dinners.