Tuesday, September 6, 2011

Modeling Antennas Using XNEC2C

So, being a linux guy, I get a little sad when people talk about how great EZ-NEC is.  It's not ported to run in a *NIX environment, and there's been mixed results using wine or virtual box.  I seriously do my best to not run non-native binaries on my computers, it's not natural, it just feels like a chimera. When W7EL releases a linux version, I'll try it out.  As a result I've been playing around with XNEC2C.

I have no idea what I'm doing.

It's ok, though, I'm learning, and so far, the learning is fun.  I picked up XNEC2C a few years ago, and thought I had it figured out.  Turns out the only thing I was doing right was drawing the pictures :) I still have to figure out how to properly model feedlines, feedpoints, and ground.  I also have to decide how particularly involved I want to get the modeling.  I usually use trees for my antennna supports.  Can the NEC2 Code handle trees? Can they be modeled? What about my neighbors metal roof?  I'm pretty sure it's doing something strange with my radiation pattern.
I can see myself getting obsessed about modeling my QTH.  How do I represent the patio, or the swingset?
It could easily get crazy, quick.
Of course I could just set everything up ideally...
"Oh what's that honey?"
"It's a model of a kite I want to fly at the beach."
"Sounds like fun!"
"Yeah, I think the kids would enjoy it"
In the meantime, I now have a reason to build a 9' tall Scott Sled!

That would sooooooo work!

Here are some pics of what I've learned so far

 W3EDP, series of pics:
W3EDP from the top, antenna running left to right

W3EDP from the side, antenna running left to right.
W3EDP from the edge, feed point is on the far end.

I tried to model the antenna like I would deploy it.  Imagine the antenna going up, as high as the end of the 'counterpoise' and then out over a branch, and slanted back toward the ground.  The section made from the 450 ohm ladder line could be supported by a collapsible fishing pole or something like that.

Click here to get the nec file, and check my data.  Copy the text, and save the file as W3EDP.nec Then you should be able to use some antenna modelling program to view it.
Let me know how it works!

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