"Wes Stewart" wrote in message
...
On Mon, 31 May 2004 15:59:31 +0100, "Richard"
wrote:

|I'm just about getting around to making my 5 or 6 element marine band
yagi,
|covering 156 - 162 Mhz RECEIVE ONLY. Do I have to employ a folded dipole

No.

|or
|can I use just a simple hertz dipole as the "driven" element? I'm trying
to
|get away from using a folded dipole if I can. Any wideband designs out
there
|that use a simple hertz dipole that I can scale? I'm looking, but if you
|have some links aready. TIA.

All dimensions in inches

X Y Z X Y Z Dia

0.000 -18.553 0.000 0.000 18.553 0.000 0.187
9.275 -18.368 0.000 9.275 18.368 0.000 0.312
12.250 -17.077 0.000 12.250 17.077 0.000 0.187
23.800 -16.672 0.000 23.800 16.672 0.000 0.187
34.213 -16.672 0.000 34.213 16.672 0.000 0.187
47.211 -16.229 0.000 47.211 16.229 0.000 0.187

IOW:
X Y Z Dia

REF End 1 0.000 -18.553 0.000 0.187
End2 0.000 18.553 0.000


DE End1 9.275 -18.368 0.000 0.312
End2 9.275 18.368 0.000


DIR1 End1 12.250 -17.077 0.000 0.187
End2 12.250 17.077 0.000


DIR2 End1 23.800 -16.672 0.000 0.187
End2 23.800 16.672 0.000


DIR4 End1 34.213 -16.672 0.000 0.187
End2 34.213 16.672 0.000


DIR5 End1 47.211 -16.229 0.000 0.187
End2 47.211 16.229 0.000

I'll see how I get along with the 4Nec2 program.

What is the DE,just a regular hertz dipole? Is DE specified as to what it is
(hertz, folded) somewhere in 4nec2?

In the Geometry Edit I see "Radius" for wire diameter I suppose. Do I
calculate the radius from the dia given in the table above? TIA.

On Wed, 2 Jun 2004 18:44:28 +0100, "Richard"
wrote:

|IOW:
yes

|I'll see how I get along with the 4Nec2 program.
|
|What is the DE,just a regular hertz dipole? Is DE specified as to what it is
|(hertz, folded) somewhere in 4nec2?

No, it's not specified as such. Modeling programs assume straight
"wires" so to model a FD you have to "construct" one from straight
wires. This is not trivial however, so don't try it until you
understand the pitfalls of "closely-spaced wires."

I strongly recommend that you download Roy's EZNEC demo, if for no
other reason than to get the excellent "Help" section.


|In the Geometry Edit I see "Radius" for wire diameter I suppose. Do I
|calculate the radius from the dia given in the table above? TIA.

Yes.


Also, when you get to building the real antenna, you have the problem
of how to feed the DE. The design in question offers a nice 50 ohm
impedance, but just opening the center and feeding directly with coax
is going to be problematic. In the Arizona desert where I live I've
gotten away with pigtailing the coax and using ferrite sleeve baluns.
Since this is a marine band antenna, I assume there's water around
someplace and that may be unsatisfactory for you.

What did you have planned?