multiPlot from 22-08-08 New England Grapes

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Bill Blackwell

Aug 9, 2022, 1:22:54 PM8/9/22

Hi Folks,

Thought I’d share the interesting multiPlots from the New England Grape group from yesterday, that show large Doppler shift and signal strength excursions, presumably during the G2 geomagnetic storm of 8-7 and 8-8. The 4 plots are in pretty good agreement.

The ”green bands” around 1400-1600 are of the type we’ve seen when the Fldigi Frequency window is accidentally incremented when a user is trying to set Op Mode to NULL, which is right above the frequency window. It can also happen when the Pi is powered down, then back up and the Bodnar freq is not yet locked or system time is not sync’ed to NTP before Fldigi starts recording. The program is designed fix these problems but I’m not sure it fixes every instance of them.

We were curious as to why the program shows these bands and the single plotter does not. The reason is that uses the fldigi-calculated Doppler shift value in the SrawData analysis[date].csv file, whereas uses data from the Sdata directory file which does not contain the calculated Doppler shift, so it calculates it from the recorded Freq value. If Freq value is off, Doppler will be off. The butterworth filter must be trying to average or smooth out the discontinuity, somehow. Thus the color bands.

I may work on a script to delay Fldigi startup until Bodnar and system time are set, as we can poll the status of both.

Thanks & 73
Bill, AB1XB


Todd Christell

Aug 9, 2022, 1:42:39 PM8/9/22
to Bill Blackwell,

I saw something similar from my V1 Grape in Missouri.


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David Kazdan

Aug 9, 2022, 2:58:59 PM8/9/22
to Hamsci-grape
Here's mine from Cleveland, also 10 MHz.  At least some of the features are similar.

Inline image


Michael Hauan

Aug 11, 2022, 8:40:55 PM8/11/22
to David Kazdan, Hamsci-grape
Here’s 5MHz from mid-Missouri.  Not as dramatic.


On Aug 9, 2022, at 13:58, David Kazdan <> wrote:

Here's mine from Cleveland, also 10 MHz.  At least some of the features are similar.



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Dr. Nathaniel A. Frissell Ph.D.

Aug 14, 2022, 1:37:18 PM8/14/22
to Michael Hauan, David Kazdan, Hamsci-grape
Hi Bill and the group,

Bill, thank you for sending your multiplot data. I am not sure why you see ringing/spikes in that particular plotting routine, but not in the single plot. I can tell you that I am working on developing an updated set of plotting tools, and I am curious if you see the same behavior there. I started with the same multiplot code you are using, but did a substantial re-write of the code. You can get new the code here: You should be able to install the code with a “pip install -e .”. I’ve been developing on Ubuntu 20.04, but it will hopefully work on Windows and Mac as well.

This code is still a work in progress, but it will absolutely do useful things now. See the "Grape V1*.ipynb” Jupyter notebooks inside You can use this notebook for MultiPlot functionality.

You will need to put the Grape data into a “data” directory inside the scripts/ directory. You can get the data we have archived so far from, and then add extra data to the directory.

You can see in the multiplot notebook that I already have the ability to plot GOES data to correlate observations with Solar Flares. We will need to eventually include Kp and a parameter called Sym-H to do the same thing with geomagnetic storms.

73 Nathaniel W2NAF

On Aug 9, 2022, at 8:45 PM, Michael Hauan <> wrote:

Here’s 5MHz from mid-Missouri.  Not as dramatic.


Bill Blackwell

Aug 15, 2022, 12:33:58 AM8/15/22
to Dr. Nathaniel A. Frissell Ph.D., Michael Hauan, David Kazdan, Hamsci-grape

Hi Nathaniel,

Thank you for sending links to the new plotting tools. We will download and try them out!

The ringing/spikes in our multiPlot Doppler graph for that day were due to the fact that uses data from the Sdata directory, which does not contain the Doppler shift calculated by Fldigi. Instead, the program calculates shift by the difference between observed frequency, based on Fldigi’s set frequency in the Frequency Window, and beaconfreq from the csv file header. If that Fldigi Frequency Window frequency is accidentally changed by the operator clicking somewhere in that window, the Fldigi frequency can be easily modified without the operator being aware of it. The butterworth filter then creates the ringing and large spikes around the discontinuity in the resulting graph.

On the other hand, the single plotter,, uses data from the Srawdata directory, which contains Doppler shift already calculated by Fldigi, which does not seem to change if the operator changes the Frequency Window entry. So the single plotter doesn’t see the glitch.

I think that if the new plotting code uses files uploaded from Sdata, it may continue to show these bands/spikes or similar, if Fldigi frequency setting is disturbed. We have thought there may be a way to lock the Fldigi frequency window, but have not looked at the code.

In the new few days I will install your new code and try it out with our data from 2022-08-08, and let you know. Thanks very much for giving us a chance to test it.

73, Bill AB1XB

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