> The old inv L and on the ground non-uniform and erratic radial system > did not cause this issue so do I conclude that the effective radiated > field from the FCP Inv l is that much stronger?
Hi Frank, When we confine a counterpoise to a small area, especially if we cancel the magnetic induction field, voltage and resulting electric induction field levels go way up. There just isn't any free lunch, no matter what the sign on the door says. When convenient, we often attribute increased problems to better performance without regard to 20 other bad things that could be at work. My wife does that with her occasional crispy blackened casseroles. > Yesterday I also did > some more work on the FCP ...when I initially built it I used 1/2inch > pressure treated wooden spacers and tie wraps. Yesterday I replaced the > those spacers with 1/2inch "PEX" (HDPE material) water pipe painted > black. These spacers appeared to cause a slight shift in the SWR curve > for the L...raising somewhat away from 1800khz. I am wondering about > this material and whether its the right stuff to use? Like the increased RFI, no one really knows what causes what without some reasonable testing or evaluation. What we do know, without a doubt, is the less spread out the counterpoise (or antenna) the more concentrated fields become. I would expect any change in spacing or dielectric to have an exaggerated effect on stub tuning (the folded counterpoise is a stub with common mode current) compared to cases where there isn't such an intense electric field. It all makes sense for multiple reasons. The question is, how much of what. If we took a big antenna and made it into a 20 foot long antenna, no matter how we did it, we would expect more sensitive tuning and higher voltages and/or currents. We would expect increased sensitivity to close surroundings. Why would we expect anything different in this case? The very fact it needs an isolation transformer with high voltage insulation tells us we have very large localized electric fields. Logically, we should expect all that comes with those voltages. 73 Tom _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK