Afaik reliable moisture measurement w/o dirty contacts etc requires microwave absorbtion measurement technology. TDR is an option if you use a bounced beam or a partially buried transmission line, but a crossed beam or transmissive CW system is simpler, larger, and harder to sell ? 2450MHz strikes me as a *very* appropriate frequency ... Of course this has nothing at all to do with 'ladder' dipoles aka open folded transmission line (which sometimes looks like a zigzag, or like a helical antenna that was run flat by a car ), patents, or microwave ovens choosing that particular frequency for operation after wise physicists found out that 2450MHz is one of the fundamental resonant frequencies of the OH- water ion, which occurs mainly in... water (liquid, and slightly ionized, as in microwaveable food and beverages, and you average garden soil). Of course they did this at least 40 years ago (I think more), but, oh my, they did not patent it. I *will* eventually patent my name if this goes on. Honest. You should too, imho. While you still can. Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.