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miv · Joined: 28 Apr 2004 Posts: 15

Dear Admin,

how do I force magnitude scale in polar mode to be non linear, logarythmic for instance, or power of 4? I can't figure it out in the current version of DPlotJr. Is that possible? If not, it would be my suggestion to add this feature.

Thank you.

DPlotAdmin · Posted: Sun May 09, 2004 12:09 am Post subject:

No, sorry, that's not currently possible. I'll confess that I've never seen a polar plot with anything but a linear scale. The only problem I have with a log scale is... where does it start? With a linear scale there's a nice, obvious relationship between the amplitude and distance to the center of the plot.
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miv · Joined: 28 Apr 2004 Posts: 15

Antenna radiation pattern is a good example. Say, values fall in 0...-60dB range (This is another question by the way - how to label the magnitude scale with negative values - please let us now, thks). Then, the beamwidth is defined as 3dB drop in power. Now try to locate the -3dB points on a polar plot with a linear scale within 60dB range. Hard, isn't it? OK, now if to make magnitude scale to be power of 4, the -3dB point moves from the outer ring closer to the center, and rests at approximately quarter of the scale. Nice! And the curve now looks better.

Thks

DPlotAdmin · Posted: Mon May 10, 2004 9:34 am Post subject:

Thanks for the example. To answer your question, you can't currently have negative radii on a polar plot. This limitation is due to my own experiences I suppose - all polar plots I've ever used depict some distance from a central point, so negative values are meaningless. I'll amend this in a future release.
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miv · Joined: 28 Apr 2004 Posts: 15

OK, just look on the Internet for a few antenna radiation pattern polar plot examples, and you'll get a very good idea what I'm talking about. The trick is that the radial scale depicts relative values (which is dB in this case), not absolute. And the reference point may take any place between the center and the outer ring. This is how you get positive and negative values.

If you could add support for this electromagnetic stuff, that would be great.
Thks