modeling capacitance hat with 4nec2 for w8jk design to wrk 40m
 

Hello.. I am interested in modeling with 4nec2 a two element W8jk for
40 meters and higher frequencies. I was thinking of using two
elements similar to the rotatable dipole described at
http://www.k6if.com/40dip/40dip.html which uses capacitance loading at
the ends of a 40' element.
I have seen how to add loading in the form of a specified capacitance
in 4nec2 but am not sure
if it is possible to just physically model the capacitance hat as if
it were just additional wire segments. Any advice would be
appreciated. I had some fun with a "bamboo beam" made
in a W8jk design with two 24' elements spaced 8' and mounted up
20' (using #10 alum. wire).
Thanks in advance for comments... Whiskey5

modeling capacitance hat with 4nec2 for w8jk design to wrk 40m
 

wrote:
... if it is possible to just physically model the capacitance hat as if
it were just additional wire segments.

It is certainly possible and is important that the top
hat wires be symmetrical around the connection point.
Whatever 'N' number of top-hat radials are modeled, the
spacing should be 360deg/N. It is easiest to model top-hat
radials in powers of 2, i.e. 4, 8, 16, ...

There's really no difference between elevated ground
plane radials and top-hat radials.
--
73, Cecil http://www.w5dxp.com
"According to the general theory of relativity,
space without ether is unthinkable." Albert Einstein

modeling capacitance hat with 4nec2 for w8jk design to wrk 40m
 

wrote:
Hello.. I am interested in modeling with 4nec2 a two element W8jk for
40 meters and higher frequencies. I was thinking of using two
elements similar to the rotatable dipole described at
http://www.k6if.com/40dip/40dip.html which uses capacitance loading at
the ends of a 40' element.
I have seen how to add loading in the form of a specified capacitance
in 4nec2 but am not sure
if it is possible to just physically model the capacitance hat as if
it were just additional wire segments. Any advice would be
appreciated. I had some fun with a "bamboo beam" made
in a W8jk design with two 24' elements spaced 8' and mounted up
20' (using #10 alum. wire).
Thanks in advance for comments... Whiskey5

The only way to model the capacitance hat is as additional wires.

The W8JK presents a low feedpoint resistance, and shortening and loading
the elements will lower it further. This will increase the potential for
loss, so you might consider including the wire resistivity in your
model. Also, the impedance of a W8JK changes rapidly with frequency, and
shortening and loading the elements will further narrow its bandwidth.
However, loss and bandwidth might be acceptable for your purpose, and
capacitive end loading won't cause as much increase in loss and decrease
in bandwidth as inductive loading would.

Roy Lewallen, W7EL