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User guide updates for frequency calibration mode
Also some instances of non-italicized WSJT-X fixed. git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@8169 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
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@ -5,7 +5,7 @@ and operation. Most of the items are self-explanatory; a few
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additional details are provided below. Keyboard shortcuts for some
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frequently used menu items are listed at the right edge of the menu.
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==== WSJT-X menu
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==== _WSJT-X_ menu
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image::MacAppMenu.png[align="left",alt="Mac App Menu"]
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This menu appears on the Macintosh only. *Settings* appears here,
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@ -44,7 +44,7 @@ successful decode used MyCall as hypothetically known information.
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|===============================================
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Table 2 lists the six possible QSO states that are tracked by the
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WSJT-X auto-sequencer, along with the type of AP decoding that would
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_WSJT-X_ auto-sequencer, along with the type of AP decoding that would
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be attempted in each state.
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[[AP_DECODING_TYPES_TABLE]]
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@ -69,6 +69,9 @@ command-prompt window:
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sudo apt remove appmenu-qt5
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+
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Alternatively, you can disable the common menu bar for just WSJT-X by starting the application with the environment variable QT_QPA_PLATFORMTHEME set to empty (the space after the '=' character is necessary):
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Alternatively, you can disable the common menu bar for just _WSJT-X_
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by starting the application with the environment variable
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QT_QPA_PLATFORMTHEME set to empty (the space after the '=' character
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is necessary):
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QT_QPA_PLATFORMTHEME= wsjtx
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@ -1,213 +1,226 @@
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=== Frequency Calibration
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Many _WSJT-X_ capabilities depend on signal-detection bandwidths no
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more than a few Hz. Frequency accuracy and stability are therefore
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unusually important. We provide tools to enable accurate frequency
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calibration of your radio, as well as precise frequency measurement of
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on-the-air signals. The calibration procedure works by automatically
|
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cycling your CAT-controlled radio through a series of preset
|
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frequencies of carrier-based signals at reliably known frequencies,
|
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measuring the error in dial frequency for each signal.
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You will probably find it convenient to define and use a special
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<<CONFIG-MENU,Configuration>> dedicated to frequency calibration.
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Then complete the following steps, as appropriate for your system.
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- Switch to FreqCal mode
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- In the _Working Frequencies_ box on the *Settings -> Frequencies*
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tab, delete any default frequencies for *FreqCal* mode that are not
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relevant for your location. You may want to replace some of them with
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reliably known frequencies receivable at your location.
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TIP: We find major-city AM broadcast stations generally serve well as
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frequency calibrators at the low frequency end of the spectrum. In
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North America we also use the standard time-and-frequency broadcasts
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of WWV at 2.500, 5.000, 10.000, 15.000, and 20.000 MHz, and CHU at
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3.330, 7.850, and 14.670 MHz. Similar shortwave signals are available
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in other parts of the world.
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- In most cases you will want to start by deleting any existing file
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`fmt.all` in the directory where your log files are kept.
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- Enter `0.0` for both *Slope* and *Intercept* under _Frequency
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Calibration_ on the *Settings -> Frequencies* tab.
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- To cycle automatically through your chosen list of calibration
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frequencies, check *Execute frequency calibration cycle* on the
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*Tools* menu. _WSJT-X_ will spend 30 seconds at each frequency,
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writing its measurements to file `fmt.all` in the log directory.
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- During the calibration procedure, the radio's USB dial frequency is
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offset 1500 Hz below each *FreqCal* entry in the default frequencies
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list. As shown in the screen shot below, detected signal carriers
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therefore appear at about 1500 Hz in the _WSJT-X_ waterfall.
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image::FreqCal.png[align="left",alt="FreqCal"]
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With modern synthesized radios, small measured offsets from 1500 Hz
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will exhibit a straight-line dependence on frequency. You can
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approximate the calibration of your radio by simply dividing the
|
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measured frequency offset (in Hz) at the highest reliable frequency by
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the nominal frequency itself (in MHz). For example, the 20 MHz
|
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measurement for WWV shown above produced a measured tone offset of
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24.6 Hz, displayed in the _WSJT-X_ decoded text window. The resulting
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calibration constant is 24.6/20=1.23 parts per million. This number
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may be entered as *Slope* on the *settings -> Frequencies* tab.
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A more precise calibration can be effected by fitting the intercept
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and slope of a straight line to the whole sequence of calibration
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measurements, as shown for these measurements in the graph plotted
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below. Software tools for completing this task are included with the
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_WSJT-X_ installation, and detailed instructions for their use are
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available at https://physics.princeton.edu/pulsar/k1jt/FMT_User.pdf.
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Using these tools and no specialized hardware beyond your
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CAT-interfaced radio, you can calibrate the radio to better than 1 Hz
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and compete very effectively in the ARRL's periodic Frequency
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Measuring Tests.
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image::FreqCal_Graph.png[align="left",alt="FreqCal_Graph"]
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After running *Execute frequency calibration cycle* at least once with
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good results, check and edit the file `fmt.all` in the log directory
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and delete any spurious or outlier measurements. The line-fitting
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procedure can then be carried out automatically by clicking *Solve for
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calibration parameters* on the *Tools* menu. The results will be
|
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displayed as in the following screen shot. Estimated uncertainties
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are included for slope and intercept; `N` is the number of averaged
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frequency measurements included in the fit, and `StdDev` is the root
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mean square deviation of averaged measurements from the fitted
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straight line.
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image::FreqCal_Results.png[align="center",alt="FreqCal_Results"]
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=== Reference Spectrum
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_WSJT-X_ provides a tool that can be used to determine the detailed
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shape of your receiver's passband. Disconnect your antenna or tune to
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a quiet frequency with no signals. With WSJT-X running in one of the
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slow modes, select *Measure reference spectrum* from the *Tools* menu.
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Wait for about a minute and then hit the *Stop* button. A file named
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`refspec.dat` will appear in your log directory.
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[ ... more to come ... ]
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=== Phase Equalization
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*Measure phase response* under the *Tools* menu is for advanced MSK144
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users. Phase equalization is used to compensate for group-delay
|
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variation across your receiver passband. Careful application of this
|
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facility can reduce intersymbol interference, resulting in improved
|
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decoding sensitivity. If you use a software-defined receiver with
|
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linear-phase filters there is no need to apply phase equalization.
|
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|
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After a frame of received data has been decoded, *Measure phase
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response* generates an undistorted audio waveform equal to the one
|
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generated by the transmitting station. Its Fourier transform is then
|
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used as a frequency-dependent phase reference to compare with the
|
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phase of the received frame's Fourier coefficients. Phase differences
|
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between the reference spectrum and received spectrum will include
|
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contributions from the originating station's transmit filter, the
|
||||
propagation channel, and filters in the receiver. If the received
|
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frame originates from a station known to transmit signals having
|
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little phase distortion (say, a station known to use a properly
|
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adjusted software-defined-transceiver) and if the received signal is
|
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relatively free from multipath distortion so that the channel phase is
|
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close to linear, the measured phase differences will be representative
|
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of the local receiver's phase response.
|
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|
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Complete the following steps to generate a phase equalization curve:
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- Record a number of wav files that contain decodable signals from
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your chosen reference station. Best results will be obtained when the
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signal-to-noise ratio of the reference signals is 10 dB or greater.
|
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- Enter the callsign of the reference station in the DX Call box.
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- Select *Measure phase response* from the *Tools* menu, and open each
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of the wav files in turn. The mode character on decoded text lines
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will change from `&` to `^` while _WSJT-X_ is measuring the phase
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response, and it will change back to `&` after the measurement is
|
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completed. The program needs to average a number of high-SNR frames to
|
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accurately estimate the phase, so it may be necessary to process
|
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several wav files. The measurement can be aborted at any time by
|
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selecting *Measure phase response* again to toggle the phase
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measurement off.
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+
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When the measurement is complete _WSJT-X_ will save the measured
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phase response in the *Log directory*, in a file with suffix
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".pcoeff". The filename will contain the callsign of the reference
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station and a timestamp, for example `K0TPP_170923_112027.pcoeff`.
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- Select *Equalization tools ...* under the *Tools* menu and click the
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*Phase ...* button to view the contents of the *Log directory*. Select
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the desired pcoeff file. The measured phase values will be plotted as
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filled circles along with a fitted red curve labeled "Proposed". This is
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the proposed phase equalization curve. It's a good idea to repeat the
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phase measurement several times, using different wav files for each
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measurement, to ensure that your measurements are repeatable.
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- Once you are satisfied with a fitted curve, push the *Apply* button
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to save the proposed response. The red curve will be replaced with a
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light green curve labeled "Current" to indicate that the phase
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equalization curve is now being applied to the received data. Another
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curve labeled "Group Delay" will appear. The "Group Delay" curve shows
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the group delay variation across the passband, in ms. Click the
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*Discard* button to remove the captured data, leaving only the applied
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phase equalization curve and corresponding group delay curve.
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- To revert to no phase equalization, push the *Restore Defaults*
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button followed by the *Apply* button.
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The three numbers printed at the end of each MSK144 decode line can be
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used to assess the improvement provided by equalization. These numbers
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are: `N` = Number of frames averaged, `H` = Number of hard bit errors
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corrected, `E` = Size of MSK eye diagram opening.
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Here is a decode of K0TPP obtained while *Measure phase response* was measuring
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the phase response:
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103900 17 6.5 1493 ^ WA8CLT K0TPP +07 1 0 1.2
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The "^" symbol indicates that a phase measurement is being accumulated
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but is not yet finished. The three numbers at the end of the line
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indicate that one frame was used to obtain the decode, there were no
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hard bit errors, and the eye-opening was 1.2 on a -2 to +2
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scale. Here's how the same decode looks after phase equalization:
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103900 17 6.5 1493 & WA8CLT K0TPP +07 1 0 1.6
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In this case, equalization has increased the eye opening from 1.2 to
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1.6. Larger positive eye openings are associated with reduced
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likelihood of bit errors and higher likelihood that a frame will be
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successfully decoded. In this case, the larger eye-opening tells us
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that phase equalization was successful, but it is important to note
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that this test does not by itself tell us whether the applied phase
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equalization curve is going to improve decoding of signals other than
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those from the reference station, K0TPP.
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It's a good idea to carry out before and after comparisons using a
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large number of saved wav files with signals from many different
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stations, to help decide whether your equalization curve improves
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decoding for most signals. When doing such comparisons, keep in mind
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that equalization may cause _WSJT-X_ to successfully decode a frame
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that was not decoded before equalization was applied. For this
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reason, be sure that the time "T" of the two decodes are the same
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before comparing their end-of-line quality numbers.
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When comparing before and after decodes having the same "T", keep in
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mind that a smaller first number means that decoding has improved,
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even if the second and third numbers appear to be "worse". For
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example, suppose that the end-of-line quality numbers before
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equalization are `2 0 0.2` and after equalization `1 5 -0.5`. These
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numbers show improved decoding because the decode was obtained using
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only a single frame after equalization whereas a 2-frame average was
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needed before equalization. This implies that shorter and/or weaker
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pings could be decodable.
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NOTE: Further details on phase equalization and examples of fitted
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phase curves and eye diagrams can be found in the article on MSK144 by
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K9AN and K1JT published in {msk144}.
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=== Frequency Calibration
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Many _WSJT-X_ capabilities depend on signal-detection bandwidths no
|
||||
more than a few Hz. Frequency accuracy and stability are therefore
|
||||
unusually important. We provide tools to enable accurate frequency
|
||||
calibration of your radio, as well as precise frequency measurement of
|
||||
on-the-air signals. The calibration procedure works by automatically
|
||||
cycling your CAT-controlled radio through a series of preset
|
||||
frequencies of carrier-based signals at reliably known frequencies,
|
||||
measuring the error in dial frequency for each signal.
|
||||
|
||||
You will probably find it convenient to define and use a special
|
||||
<<CONFIG-MENU,Configuration>> dedicated to frequency calibration.
|
||||
Then complete the following steps, as appropriate for your system.
|
||||
|
||||
- Switch to FreqCal mode
|
||||
|
||||
- In the _Working Frequencies_ box on the *Settings -> Frequencies*
|
||||
tab, delete any default frequencies for *FreqCal* mode that are not
|
||||
relevant for your location. You may want to replace some of them with
|
||||
reliably known frequencies receivable at your location.
|
||||
|
||||
TIP: We find major-city AM broadcast stations generally serve well as
|
||||
frequency calibrators at the low frequency end of the spectrum. In
|
||||
North America we also use the standard time-and-frequency broadcasts
|
||||
of WWV at 2.500, 5.000, 10.000, 15.000, and 20.000 MHz, and CHU at
|
||||
3.330, 7.850, and 14.670 MHz. Similar shortwave signals are available
|
||||
in other parts of the world.
|
||||
|
||||
- In most cases you will want to start by deleting any existing file
|
||||
`fmt.all` in the directory where your log files are kept.
|
||||
|
||||
- To cycle automatically through your chosen list of calibration
|
||||
frequencies, check *Execute frequency calibration cycle* on the
|
||||
*Tools* menu. _WSJT-X_ will spend 30 seconds at each
|
||||
frequency. Initially no measurement data is saved to the `fmt.all`
|
||||
file although it is displayed on screen, this allows you to check you
|
||||
current calibration parameters.
|
||||
|
||||
- During the calibration procedure, the radio's USB dial frequency is
|
||||
offset 1500 Hz below each *FreqCal* entry in the default frequencies
|
||||
list. As shown in the screen shot below, detected signal carriers
|
||||
therefore appear at about 1500 Hz in the _WSJT-X_ waterfall.
|
||||
|
||||
- To start a measurement session check the *Measure* option and let
|
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the calibration cycle run for at least one complete sequence. Note
|
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that, while measuring, any existing calibration parameters are
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automatically disabled so you may have to increase the *FTol* range if
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your rig is off freqeuncy by more than a few Hertz in order to capture
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valid measurements.
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||||
|
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image::FreqCal.png[align="left",alt="FreqCal"]
|
||||
|
||||
With modern synthesized radios, small measured offsets from 1500 Hz
|
||||
will exhibit a straight-line dependence on frequency. You can
|
||||
approximate the calibration of your radio by simply dividing the
|
||||
measured frequency offset (in Hz) at the highest reliable frequency by
|
||||
the nominal frequency itself (in MHz). For example, the 20 MHz
|
||||
measurement for WWV shown above produced a measured tone offset of
|
||||
24.6 Hz, displayed in the _WSJT-X_ decoded text window. The resulting
|
||||
calibration constant is 24.6/20=1.23 parts per million. This number
|
||||
may be entered as *Slope* on the *settings -> Frequencies* tab.
|
||||
|
||||
A more precise calibration can be effected by fitting the intercept
|
||||
and slope of a straight line to the whole sequence of calibration
|
||||
measurements, as shown for these measurements in the graph plotted
|
||||
below. Software tools for completing this task are included with the
|
||||
_WSJT-X_ installation, and detailed instructions for their use are
|
||||
available at https://physics.princeton.edu/pulsar/k1jt/FMT_User.pdf.
|
||||
|
||||
Using these tools and no specialized hardware beyond your
|
||||
CAT-interfaced radio, you can calibrate the radio to better than 1 Hz
|
||||
and compete very effectively in the ARRL's periodic Frequency
|
||||
Measuring Tests.
|
||||
|
||||
image::FreqCal_Graph.png[align="left",alt="FreqCal_Graph"]
|
||||
|
||||
After running *Execute frequency calibration cycle* at least once with
|
||||
good results, check and edit the file `fmt.all` in the log directory
|
||||
and delete any spurious or outlier measurements. The line-fitting
|
||||
procedure can then be carried out automatically by clicking *Solve for
|
||||
calibration parameters* on the *Tools* menu. The results will be
|
||||
displayed as in the following screen shot. Estimated uncertainties
|
||||
are included for slope and intercept; `N` is the number of averaged
|
||||
frequency measurements included in the fit, and `StdDev` is the root
|
||||
mean square deviation of averaged measurements from the fitted
|
||||
straight line. If the solution seems valid you will be offered an
|
||||
*Apply* button to push that will automatically set the calibration
|
||||
parameters in *Settings -> Frequencies -> Frequency Calibration*.
|
||||
|
||||
image::FreqCal_Results.png[align="center",alt="FreqCal_Results"]
|
||||
|
||||
For a quick visual check of the resulting calibration, stay in
|
||||
*FreqCal* mode with the *Measure* option cleared. _WSJT-X_ will show
|
||||
the adjusted results directly on the waterfall and the displayed
|
||||
records.
|
||||
|
||||
=== Reference Spectrum
|
||||
|
||||
_WSJT-X_ provides a tool that can be used to determine the detailed
|
||||
shape of your receiver's passband. Disconnect your antenna or tune to
|
||||
a quiet frequency with no signals. With _WSJT-X_ running in one of
|
||||
the slow modes, select *Measure reference spectrum* from the *Tools*
|
||||
menu. Wait for about a minute and then hit the *Stop* button. A file
|
||||
named `refspec.dat` will appear in your log directory.
|
||||
|
||||
[ ... more to come ... ]
|
||||
|
||||
=== Phase Equalization
|
||||
|
||||
*Measure phase response* under the *Tools* menu is for advanced MSK144
|
||||
users. Phase equalization is used to compensate for group-delay
|
||||
variation across your receiver passband. Careful application of this
|
||||
facility can reduce intersymbol interference, resulting in improved
|
||||
decoding sensitivity. If you use a software-defined receiver with
|
||||
linear-phase filters there is no need to apply phase equalization.
|
||||
|
||||
After a frame of received data has been decoded, *Measure phase
|
||||
response* generates an undistorted audio waveform equal to the one
|
||||
generated by the transmitting station. Its Fourier transform is then
|
||||
used as a frequency-dependent phase reference to compare with the
|
||||
phase of the received frame's Fourier coefficients. Phase differences
|
||||
between the reference spectrum and received spectrum will include
|
||||
contributions from the originating station's transmit filter, the
|
||||
propagation channel, and filters in the receiver. If the received
|
||||
frame originates from a station known to transmit signals having
|
||||
little phase distortion (say, a station known to use a properly
|
||||
adjusted software-defined-transceiver) and if the received signal is
|
||||
relatively free from multipath distortion so that the channel phase is
|
||||
close to linear, the measured phase differences will be representative
|
||||
of the local receiver's phase response.
|
||||
|
||||
Complete the following steps to generate a phase equalization curve:
|
||||
|
||||
- Record a number of wav files that contain decodable signals from
|
||||
your chosen reference station. Best results will be obtained when the
|
||||
signal-to-noise ratio of the reference signals is 10 dB or greater.
|
||||
|
||||
- Enter the callsign of the reference station in the DX Call box.
|
||||
|
||||
- Select *Measure phase response* from the *Tools* menu, and open each
|
||||
of the wav files in turn. The mode character on decoded text lines
|
||||
will change from `&` to `^` while _WSJT-X_ is measuring the phase
|
||||
response, and it will change back to `&` after the measurement is
|
||||
completed. The program needs to average a number of high-SNR frames to
|
||||
accurately estimate the phase, so it may be necessary to process
|
||||
several wav files. The measurement can be aborted at any time by
|
||||
selecting *Measure phase response* again to toggle the phase
|
||||
measurement off.
|
||||
|
||||
+
|
||||
|
||||
When the measurement is complete _WSJT-X_ will save the measured
|
||||
phase response in the *Log directory*, in a file with suffix
|
||||
".pcoeff". The filename will contain the callsign of the reference
|
||||
station and a timestamp, for example `K0TPP_170923_112027.pcoeff`.
|
||||
|
||||
- Select *Equalization tools ...* under the *Tools* menu and click the
|
||||
*Phase ...* button to view the contents of the *Log directory*. Select
|
||||
the desired pcoeff file. The measured phase values will be plotted as
|
||||
filled circles along with a fitted red curve labeled "Proposed". This is
|
||||
the proposed phase equalization curve. It's a good idea to repeat the
|
||||
phase measurement several times, using different wav files for each
|
||||
measurement, to ensure that your measurements are repeatable.
|
||||
|
||||
- Once you are satisfied with a fitted curve, push the *Apply* button
|
||||
to save the proposed response. The red curve will be replaced with a
|
||||
light green curve labeled "Current" to indicate that the phase
|
||||
equalization curve is now being applied to the received data. Another
|
||||
curve labeled "Group Delay" will appear. The "Group Delay" curve shows
|
||||
the group delay variation across the passband, in ms. Click the
|
||||
*Discard* button to remove the captured data, leaving only the applied
|
||||
phase equalization curve and corresponding group delay curve.
|
||||
|
||||
- To revert to no phase equalization, push the *Restore Defaults*
|
||||
button followed by the *Apply* button.
|
||||
|
||||
The three numbers printed at the end of each MSK144 decode line can be
|
||||
used to assess the improvement provided by equalization. These numbers
|
||||
are: `N` = Number of frames averaged, `H` = Number of hard bit errors
|
||||
corrected, `E` = Size of MSK eye diagram opening.
|
||||
|
||||
Here is a decode of K0TPP obtained while *Measure phase response* was measuring
|
||||
the phase response:
|
||||
|
||||
103900 17 6.5 1493 ^ WA8CLT K0TPP +07 1 0 1.2
|
||||
|
||||
The "^" symbol indicates that a phase measurement is being accumulated
|
||||
but is not yet finished. The three numbers at the end of the line
|
||||
indicate that one frame was used to obtain the decode, there were no
|
||||
hard bit errors, and the eye-opening was 1.2 on a -2 to +2
|
||||
scale. Here's how the same decode looks after phase equalization:
|
||||
|
||||
103900 17 6.5 1493 & WA8CLT K0TPP +07 1 0 1.6
|
||||
|
||||
In this case, equalization has increased the eye opening from 1.2 to
|
||||
1.6. Larger positive eye openings are associated with reduced
|
||||
likelihood of bit errors and higher likelihood that a frame will be
|
||||
successfully decoded. In this case, the larger eye-opening tells us
|
||||
that phase equalization was successful, but it is important to note
|
||||
that this test does not by itself tell us whether the applied phase
|
||||
equalization curve is going to improve decoding of signals other than
|
||||
those from the reference station, K0TPP.
|
||||
|
||||
It's a good idea to carry out before and after comparisons using a
|
||||
large number of saved wav files with signals from many different
|
||||
stations, to help decide whether your equalization curve improves
|
||||
decoding for most signals. When doing such comparisons, keep in mind
|
||||
that equalization may cause _WSJT-X_ to successfully decode a frame
|
||||
that was not decoded before equalization was applied. For this
|
||||
reason, be sure that the time "T" of the two decodes are the same
|
||||
before comparing their end-of-line quality numbers.
|
||||
|
||||
When comparing before and after decodes having the same "T", keep in
|
||||
mind that a smaller first number means that decoding has improved,
|
||||
even if the second and third numbers appear to be "worse". For
|
||||
example, suppose that the end-of-line quality numbers before
|
||||
equalization are `2 0 0.2` and after equalization `1 5 -0.5`. These
|
||||
numbers show improved decoding because the decode was obtained using
|
||||
only a single frame after equalization whereas a 2-frame average was
|
||||
needed before equalization. This implies that shorter and/or weaker
|
||||
pings could be decodable.
|
||||
|
||||
NOTE: Further details on phase equalization and examples of fitted
|
||||
phase curves and eye diagrams can be found in the article on MSK144 by
|
||||
K9AN and K1JT published in {msk144}.
|
||||
|
@ -1,6 +1,6 @@
|
||||
// Status=review
|
||||
|
||||
image::settings-audio.png[align="center",alt="WSJT-X Audio Configuration Screen"]
|
||||
image::settings-audio.png[align="center",alt="_WSJT-X_ Audio Configuration Screen"]
|
||||
|
||||
Select the *Audio* tab to configure your sound system.
|
||||
|
||||
|
@ -1,5 +1,5 @@
|
||||
// This is a comment line, anything with // is ignored at process time.
|
||||
= WSJT-X User Guide
|
||||
= _WSJT-X_ User Guide
|
||||
Joseph H Taylor, Jr, K1JT
|
||||
:revnumber: {VERSION}
|
||||
// For web-pages, adding :badges: is ok, but is a security issue for
|
||||
|
Loading…
Reference in New Issue
Block a user