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Author Topic: Modeling trap dipoles in EZNEC  (Read 1279 times)
VE7EPQ
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Posts: 5




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« on: December 22, 2009, 07:45:59 PM »

I am starting work on EZNEC and I am having a terrible time modeling a simple dipole with traps that will work.  I have not been able to find a listing on the web where someone has done a primer on this to help newbies to EZNEC model something like this.
Wanting to model an 80/40/30 dipole with traps.
If possible, I want to model the loads as RLC with known R freq. so multiple frequencies can be viewed.
Anyone know where to start?

Mike Donovan  VE7EPQ
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G3TXQ
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Posts: 1534




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« Reply #1 on: December 23, 2009, 04:08:44 AM »

I am starting work on EZNEC and I am having a terrible time modeling a simple dipole with traps that will work.  I have not been able to find a listing on the web where someone has done a primer on this to help newbies to EZNEC model something like this.
Wanting to model an 80/40/30 dipole with traps.
If possible, I want to model the loads as RLC with known R freq. so multiple frequencies can be viewed.
Anyone know where to start?

Mike Donovan  VE7EPQ
Mike,

Can you be more specific about what problems you are having?

It should be possible to do this with a single wire. Give the wire a large, odd, number of segments, and place the source at the 50% point. Next place two identical RLC loads equidistant from the centre - for example at 25% and 75%. Adjust the LC values for trap resonance at the required frequency, and R for an appropriate Q value.

That should work - it just becomes a bit "finickey" when you are trying to adjust trap positions and overall wire length.

Hope that helps some.

Steve G3TXQ
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W8JI
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« Reply #2 on: December 23, 2009, 04:17:47 AM »

I am starting work on EZNEC and I am having a terrible time modeling a simple dipole with traps that will work.  I have not been able to find a listing on the web where someone has done a primer on this to help newbies to EZNEC model something like this.
Wanting to model an 80/40/30 dipole with traps.
If possible, I want to model the loads as RLC with known R freq. so multiple frequencies can be viewed.
Anyone know where to start?

Mike Donovan  VE7EPQ

Mike,

You want to change to L/C/R traps in Eznec. Go to loads menu tab, then to "other", and change to "change load type".

Does that help?

Tom
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VE7EPQ
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Posts: 5




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« Reply #3 on: December 27, 2009, 05:28:38 PM »

I was entering the reactive component of the trap as the R resistive component.  It made no sense to the software.  Another ham off-lined me an example from Eznec and I immediately saw my mistake.  I have modelled two antennas now and have taken on the project of building one.
This software is utterly fantastic.
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