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Software Cont’d
PolarPlot:
PolarPlot is a freeware program written by Bob Freeth, G4HFQ. It is designed mainly to create polar antenna plots from power samples, but it can also
produce histograms of power over time. Combined with the nifty Field Strength feature of the LP-100A, PolarPlot provides a slick way to plot beam
patterns, calculate gain, etc. I have added support for PolarPlot in LP-100A_VCP ver. 1.0.7.
Here are some links to PolarPlot 3.2.0 for downloading the program and help file.
Bob’s main web page
http://www.g4hfq.co.uk/download.html
– download page
http://s4468.gridserver.com/g4hfq/PolarPlotSetup.exe
– direct link to installation file
http://www.g4hfq.co.uk/plphelp/plphelp.htm
– direct link to help file
I will not go into detail here on the use of PolarPlot, but I will briefly discuss the basic operation as it pertains to the LP-100A. The basic setup would be
to set the LP-100A up for operation in Field Strength mode (sampling antenna plugged into one of the ports on the back of the main LP-100A chassis).
This will allow you to plot received levels in the
–15 dBm to +33 dBm range. This range should work well for HF/6m antenna plotting. The sampling
antenna can either be the beam under test, or a small dipole. In the case of the beam, a neighbor in the far field (~10 wavelengths away) or a remote
transmitter of sufficient power supplies the signal. Alternatively, the sampling antenna can be a small dipole, with the transmitter connected to the beam.
In this case, good isolation of the feedline to the remote antenna would be needed, or the LP-100A located remotely with a laptop computer which would
allow remote control of the LP-100A.
To use PolarPlot with the LP-100A, you just need to set the LP-100A up for Field Strength measurement, launch VCP and then launch PolarPlot. In
PolarPlot, you select LP-100A by clicking on the Choose Input button, and clicking on the LP-100A entry. A "dB Meter" dialog box will pop up showing
9999 as the current signal level from the LP-100A. Transmit with the beam pointed at 0 degrees (front), and double-click on Calibrate. You will see a
new reading in the dB Meter window. Click on the wide button that says "Calibrate the current reading as 0dB". This will set the outer 0dB ring of the
plot to maximum.
Next, set the Rotation Time slider for the time it takes your rotator to turn 360 degrees. All that is necessary now is to start the rotator at 0 degrees and
click the "Collect Data" button at the same time. If your rotator is not consistent in its timing, you can set the time for a little longer than a rotation takes,
and when the rotator reaches 360 degrees, click on the Halt Collection button, and then the Rescale button. This will rescale the plot both in amplitude
and azimuth, spreading the collected data equally over 360 degrees. It also "fattens up" the dotted curve. There is no harm in using this button just to
fatten up curves, even if your rotator is consistent.
Double clicking in the plot area will open a setup screen where you can change colors, etc. I find making the lines gray and the plots red provides better
contrast, but you can play with it.
Refer to Bob's help file or email me for help. Bob and I are both interested in feedback on this.
Summary of Contents for LP-100A
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