Display/Save currents

xnec2c v4.4.16 on Kubuntu 24.04. 14MHz folded dipole, centre excited with 77V (P=20W) set with Z0 = 300 Ohm, resonant on 14.239MHz

When I run the model and select "view currents," the graduated colour scale is missing (bug?) but at the resonant frequency it shows the max current as 2.59E-1 Amps on screen. Plugging this back into the usual formula with P gives R of 298 Ohms as expected.

When I select a frequency of 14.239MHz in the "view currents" window and then File > save currents/charges as CSV, I have a file with the correct frequency in column A but for no tag/segment do I see a current of 2.59E-1 Amps, they are all very much smaller.

I may very well be misunderstanding or doing something wrong. Files attached. Any advice?

Ian G4IXT

(Supplementary Question: What units are "charges" in and is there any way to relate them to Voltage on the wire?)
g4ixt_folded_v8_14MHz.tar.gz

@neoklis

When I run the model and select "view currents," the graduated colour scale is missing (bug?)

that is strange the color scale works on my screen, so maybe it is a distribution issue? but let's get to the math problem:

but at the resonant frequency it shows the max current as 2.59E-1 Amps on screen. Plugging this back into the usual formula with P gives R of 298 Ohms as expected.
...
have a file with the correct frequency in column A but for no tag/segment do I see a current of 2.59E-1 Amps, they are all very much smaller.

In Draw_Wire_Segments(), when displaying currents, the code shows:

if( isFlagSet(DRAW_CURRENTS) )
  snprintf( label, s, "%8.2E", cmax * (double)data.wlam );

The displayed current is scaled by wavelength (data.wlam), but in Save_Currents_CSV() the raw current values are saved without this scaling.

So, cabs(real+imag*i)*lambda will probably yield 2.59E-1 for some tag/seg?

Can you confirm that that works for you in the spreadsheet?

If this looks right to you then I will update the function to include a magnitude column scaled by wavelength, but I have another question, too:

Do you believe that the complex and real value should also be scaled by wave length when writing to the CSV? I am not so familiar with the math here (as I am just the maintainer), so your help would be appreciated.

@neoklis, can you comment on this?

(FYI, CSV current/charge save feature was added in 0018d01 for #34)

see attached does this look correct?

g4ixt_folded_v8_14MHz-currents2.csv

I believe this is complete and solved, but reopen the issue if the problem persists.

and I forgot to mention, if you build this from git then you will have the latest version that contains the fix:

git clone https://github.com/KJ7LNW/xnec2c.git
cd xnec2c
./autogen.sh
./configure
make
./src/xnec2c # test from source tree w/o install

optional:

apt remove xnec2c
make install
make desktop-install # Optional: for icons and file association.
xnec2c # installed from git

Hi Eric! Best season's greetings to you and Zeke!

> When I run the model and select "view currents," the graduated colour scale is missing (bug?)

I don't know about this. I think it may happen if min and max values are the same, if possible. But I have never experienced this.

So, cabs(real+imag*i)*lambda will probably fix it?

I think so too, did you get the right results in the CSV?

Do you believe that the complex and real value should also be scaled by wave length when writing to the CSV? I am not so familiar with the math here (as I am just the maintainer), so your help would be appreciated.

I think they should be, the absolute scalar value cmag is calculated from them and if you want to print the real and complex parts of it, they should be scaled.

…

-- Best Regards Neoklis - Ham Radio Call: 5B4AZ http://www.5b4az.org/ https://www.qsl.net/5b4az/index.html

Awesome, thanks! See 01c9bef for the diff. This fixed both current and charge scaling and added magnitude columns.

see attached does this look correct?

g4ixt_folded_v8_14MHz-currents2.csv

Yes, that looks correct, thank you.

Ian

When I run the model and select "view currents," the graduated colour scale is missing (bug?)
that is strange the color scale works on my screen, so maybe it is a distribution issue?

It turns out to be a window size issue. Since it worked ok for you I thought to try changing the window size (I had 3 windows 'docked' on my widescreen monitor). As soon as I changed the size, the graduated colour scale appeared.

gnuplot: add current magnitude and scale currents/charges in CSV output

Release v4.4.17

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Display/Save currents #61

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KJ7LNW commented on Dec 28, 2024

KJ7LNW commented on Dec 28, 2024

KJ7LNW commented on Dec 28, 2024

KJ7LNW commented on Dec 29, 2024

KJ7LNW commented on Dec 29, 2024

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neoklis commented on Dec 29, 2024

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g4ixt commented on Dec 29, 2024

g4ixt commented on Dec 29, 2024

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