ESPcat Self Isolating

There is my friend John next to Borderline, self isolating on the mud in Oneroa Bay, Waiheke Island.  John and I spent the night there.  We may have misjudged the tide a bit.  It’s a mistake anyone could have made.  DSC_0480

These photos were taken before the world went mad.  Too bad about the upcoming depression and economic collapse not to mention the ………………!  I don’t think it is going to be particularly good but there are always opportunities.  I prefer a positive attitude.

Here is an opportunity.  I decided I wanted an even better VHF marine antenna than the inside, coaxial, collinear 3 dBi unit I built.  My inside antenna works well but I wanted more so I built the Super Gold antenna.super antenna

It’s a super j-pole about 2.5 meters tall with a 9 dBi gain!  I built it after I discovered that all the commercially available VHF marine antennas were a load of nonsense.  For starters, many of them are made from stainless steel which is a lousy conductor of electricity.  Stainless steel has 42.9 times the resistance of copper.  Stainless steel also has iron in it so that makes it even more lousy for making antennas.  If you don’t care about hearing or being heard, get yourself a nice stainless steel antenna.

Then there is all the marketing bullshit that antenna manufacturers use like the meaningless term “marine gain”.  Marine gain is just the real gain in dBi with 3 dB added to it for no scientific reason what-so-ever.   On top of that the actual gain in dBi that most quote is just a dream that nobody has bothered to verify.

Many commercial antennas don’t have an SWR of less than 1.2 as their manufacturers claim so that much of your transmitter’s power doesn’t make it out the antenna.  Rather the power gets reflected back to the transmitter and wasted as heat.   I have never seen a marine VHF antenna with adjustable SWR like my Super Gold antenna has.  How can you take into account the effect on SWR of objects close to your antenna once it is installed if there is no adjustment?  So even if your commercial antenna had a 1:1 SWR when it was sold, it will not have a decent SWR once it’s installed. *

Another popular commercial trick is to take a 3 dBi antenna and mount it inside a long (2.5 m) pole and claim that it has wonderful performance.  Look at the specifications and many of these big antennas only have a gain of 3dBi.  You are paying a lot of money for a fiberglass pole.  Yes, your antenna will theoretically work better mounted higher up, but not by much.

My 9 dBi, Super Antenna is amazing.  You can hear a fly fart 50 miles away on my VHF marine radio and all the boaties can hear me fart too! When I talk, I want everyone to listen especially if I’m self isolating.

* SWR is a measure of the power from your transmitter compared to the reflected power.  An SWR of 1:1 means all the transmitter’s power gets to the antenna.  An SWR of 2:1 means you are wasting 11% of your transmitter’s power.  An SWR of 3:1 and you loose 25% of your transmitter’s power.  At 4:1 (the SWR of the commercial antenna I use for testing) I am losing 36%! https://www.arrl.org/files/file/Technology/tis/info/pdf/q1106037.pdf

 

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