[Elecraft] New antenna (Definitely OT)

[Kok Chen]

On 10/17/2010 1:40 AM, Jan Erik Holm wrote:

> This will go nicely with my K3
> http://www.youtube.com/watch?v=9tIZUhu21sQ

Seawater has electrical conductivity of seven *orders* of magnitude  
lower than copper!

As a quick and dirty check, I created a simple 10m ground plane  
antenna in NEC-4.  Four counterpoises and a vertical radiating element  
that is bottom fed, all of equal lengths, with the counterpoises and  
the feedpoint 1m above seawater (natch!) ground.  All elements 0.5" in  
diameter.

With perfectly conducting elements, the feedpoint impedance is just  
about 35 ohms, with a gain of 4.7 dBi.

When I changed the conductivity of the vertical element to 5 mhos/ 
meter, while keeping the counterpoises as perfectly conducting, the  
computed gain dropped to -8.2 dBi and the feedpoint impedance is  
capacitive at 320 -i*250 ohms.

I.e., something like 13 dB loss compared to using copper elements.

BTW, I could not achieve resonance by extending the length of the  
radiating element --  I guess you will need a KAT500 in addition to  
that KPA500 which you use to make up for the missing 13 dB.

This could make a good water heater.  All that power has to go  
*somewhere* :-).

73
Chen, W7AY