Topband: Problems with inv L on pier over salt water

[Gary K9GS]

Hi Cecil,No...you don't want your counterpoise in the water. The reason is that RF does not penetrate very far into salt water.The only exception would be if the water was only a few inches deep like in a salt marsh.73,Gary K9GS
-------- Original message --------From: Cecil <chacuff at cableone.net> Date: 1/8/20  12:01 PM  (GMT-06:00) To: Ignacy Misztal <no9e at arrl.net> Cc: Topband at contesting.com Subject: Re: Topband: Problems with inv L on pier over salt water 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...CecilK5DL> On Jan 8, 2020, at 11:07 AM, Ignacy Misztal <no9e at arrl.net> 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