Antenna Toolbox simulations come out wrong

I did the following with the Antenna Designer from the Antenna Toolbox:

1. Open Antenna Designer App
2. Click "New"
3. Choose "Monopole" from the "Antenna Gallery"
4. Enter "Design Frequency" of 10 MHz
5. Click "Accept"
6. Set "GroundPlaneLength" and "GroundPlaneWidth" to "Inf"
7. Set "Width" to 0.01
8. Click "Apply"
9. Click "Impedance" under "Vector Frequency Analysis"

Here's the model displayed in the designer:

And I observe that the resistance at resonance (where reactance is 0) is about 22 ohms. This is really far off from a proper calculation of a quarter wave monopole over a perfect, infinite ground plane.

If you use 4NEC, MMANA, etc., you'll find that the resistance will come out to about 36 ohms. And if you build a real quarter wave monopole over a large, flat ground plane, you'll measure approximately the same with a VNA. Here's an example simulation of the same antenna in MMANA:

What am I doing wrong? I have trouble thinking that the Antenna toolbox would be so wrong on such a fundamentally simple antenna model... so I assume I'm not doing something correctly. The documentation doesn't seem to add any extra help, so I hope I can find someone to give me a nudge in the right direction!

Answer 1

[Mike Croucher]

Hi @Joshua. I've reported this to development who think this may be a bug and are currently investigating. Thank you for the report