I’m far from an expert but if you were over salt water I would have placed the counterpoise in the water.
I’d be curious what others think. Great experience though... Cecil K5DL > On Jan 8, 2020, at 11:07 AM, Ignacy Misztal <[email protected]> wrote: > > I would like to share my experiences with 160m operations during the SP > contest last December. > > My rental house in St George Isl FL had a 140 ft pier over the bay. Also a > power line to the end of the pier raising questions about RFI. > > I set inv L at the end of the pier with 40ft Spiderpole, 70ft horizontal > and 70ft radial on the pier. Horizontal with 24 gauge enameled wire for > low weight, and the rest with 18 ga THHN. Matching was with a transformer > on FT140-61 and coil on T200-2. Minimal SWR at 1.84. > > One hr before the sunset the EU was booming. RFI was pretty high but the > signals even stronger. I tried to use KX3 and Expert 1.3k combination, but > SWR become very unstable causing the Expert to turn off. I was looking for > culprits but could not find anything. Frustrated, I was forced to use > FT-891 at 100W. > > The setup was still pretty good as several EU answered my CQ. > > The next day I noticed that the radial on the pier that was touching > underneath (salt water sprayed) had melted insulation. Apparently this > caused sparcing and then variations in SWR. > > I relocated the radial away from the pier, over the bay. The resonance > moved from 1.84 to 1.96, and the impedance at resonance reduced from 40 to > 25 ohms. So the pier (or power line) was loading the antenna, surely > generating losses. Operating with a KW was no longer a problem. > > Here are my lessons: > 1. 40ft Spiderpole is enough for highly efficient inv L over salt water. > 2. Beware of insulated wire touching anything and especially wet and salty > at high power. > 3. Even with problems, the performance of an antenna over salt water is > terrific. > 4. Matching units do not have to be big. > 5. With good antenna, $550 FT-891 is OK. > > Ignacy, NO9E > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
