FLDIGI Users Manual  3.21
Frequency Analyzer



Fldigi can be used to accurately measure the frequency of a remote signal that is transmitting a steady carrier.

FreqAnal.png
Frequency Analyzer

I have set the sound card up using the WWV modem and have it adjusted for the proper PPM offset on receive. I followed the frequency calibration procedure for the FT-950, adjusting the WWV carrier signal for exactly 1000 Hz with the transceiver tuned to 9999.0 MHz. The FT-950 provides the user with a digital adjustment to the reference frequency, Menu 035.

Then fldigi was used in the "Freq Analysis" mode to track the WWV carrier at 10 MHz. In this mode the decoder measures the frequency of the marked signal using DFT-based parameter estimator as described by Tsui and Reisenfeld in the January 2006 issue of the Jornal of Telecommunications and Information Technoloby, "A highly accurate DFT-based parameter estimator for complex expontials." The digiscope is not used. During the measurement both the estimated signal and it's s/n will be displayed in the two left two status bar report controls. The 3rd status bar control will be blank or indicate that the measurements are being recorded to a file, "writing csv file."

The data file is named "analysis.csv" and is written to the files temp directory. The format is:

Clock Error --1 1 Audio RF
1 0.06 -1 1 1000.06 10000000.0602
2 0.043 -1 1 1000.043 10000000.0434
3.1 0.04 -1 1 1000.04 10000000.0398
4.1 0.03 -1 1 1000.03 10000000.0298
5.1 0.027 -1 1 1000.027 10000000.0274
6.1 0.022 -1 1 1000.022 10000000.0223
7.2 0.018 -1 1 1000.018 10000000.0177
8.2 0.013 -1 1 1000.013 10000000.0132
9.2 0.009 -1 1 1000.009 10000000.0093
10.2 0.004 -1 1 1000.004 10000000.0040
11.3 0.001 -1 1 1000.001 10000000.0008
12.3 -0.002 -1 1 999.998 9999999.9978
13.3 -0.006 -1 1 999.994 9999999.9944


Clock is in seconds for the start of the recording
Error is in Hz, from the selected waterfall frequency
The +/-1 are simply data point to make it convenient to display a graph in a spreadsheet program.
Audio is the estimated audio tracking frequency in Hz.
RF is the estimated radio frequency tracking frequency in Hz.

analysis_csv.png
Frequency Analysis

The analysis.csv file will be cleared and restarted every time that the waterfall tracking point is changed by the operator, using either the WF cursor left click, or the WF frequency selection control.

A new macro tag has been added to assist the operator to manage the recording:
<CSV:on|off|t>
on - restart file,
off - stop recording,
t - toggle on/off


ARRL frequently announces a frequency measurement test (FMT) which takes place on 160, 80 and 40 meters. This is a chance to test your skills in frequency measurement. You should be able to make a submission to the FMT using this technique. Make corrections to the FMT transmission based upon your WWV measurement. You may have to adjust for other local oscillator effects as well. If you have some good ways to measure and correct for these I would be glad to share them with the other fldigi users.


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