QUISK Help File

QUISK Help (January 2011)

This is the Help file for Quisk, a Software Defined Radio (SDR). This Help appears in Quisk when you press the Help button. Quisk is written by Jim Ahlstrom, N2ADR, www.james.ahlstrom.name. Mail to quisk at james.ahlstrom.name. Quisk has been greatly improved and extended by Leigh L. Klotz Jr. WA5ZNU, and by Andrew Nilsson VK6JBL. Thanks to Terry Fox WB4JFI for code improvements, and for adding support for the Charleston hardware. Thanks to Sid Boyce, G3VBV, for sending me SoftRock hardware to work with.

What Quisk Can Do

Depending on how you have configured it, Quisk can be used as a radio receiver, a transceiver, or a panadapter. When you use Quisk as a receiver or panadapter, you supply an antenna, a complex (I/Q) mixer to convert radio spectrum to a low IF, and send that IF to the left and right inputs of the sound card in your computer. The Quisk software will read the sound card data, tune it, filter it, demodulate it, and send the audio to the same sound card for output to external headphones or speakers. For most efficient use, you may wish to configure some form of rig control in the your configuration file and hardware file.

Quisk can also accept I/Q data from the SDR-IQ from RfSpace. The selection of SDR-IQ or soundcard is made in your configuration file.

Quisk rhymes with "brisk", and is QSK plus a few letters to make it easier to pronounce. QSK is a Q signal meaning full break in CW operation, and Quisk has been designed for low latency. Quisk includes an input keying signal that can mute the audio and substitute a side tone. To install and configure Quisk, please see the docs.html file in the Quisk directory.

Quisk is designed for QSK CW operation. It is written in Python, an easy to learn but powerful language; see www.python.org. Source is provided because your own hardware is probably different from mine, and you will need to change something. Changing Python is easy.

There are lots of other SDR projects; see the list at http://f4dan.free.fr/sdr_eng.html. I particularly recommend Linrad by SM5BSZ, PowerSDR, and SDRadio by I2PHD. Reading the Linrad pages is a great introduction to SDR.

Configuration File

Quisk first imports all its configuration information from the file quisk_conf_defaults.py. Then it reads your configuration file. To change your configuration, do NOT change quisk_conf_defaults.py, because installing the next version will cause your changes to be lost. Instead copy one of the sample quisk_conf_*.py to your config file. For a standard soundcard, copy quisk_conf_model.py. Make any changes you want to your config file. To see what kinds of changes are available, read the file quisk_conf_defaults.py. Please do NOT copy quisk_conf_defaults.py to your config file. Your config file should consist of only the lines that are different from quisk_conf_defaults.py, and it should be a small file.

The configuration file also imports your hardware control file. This is quisk_hardware_model by default. To use a different hardware file add "import quisk_hardware_fixed as quisk_hardware" (for SoftRock, or another quisk_hardware_* file) to your configuration file. You can control your own hardware either by writing a custom hardware file, or by defining a "class Hardware" in your config file. See docs.html for details, and read the various hardware files.

If you need to add custom controls to Quisk, add "import quisk_widgets_mywidgets as quisk_widgets" to your configuration file, and see quisk_widgets_n2adr.py. This is an advanced feature, and you will need to understand wxPython.

Testing QUISK

Look at the bottom row of buttons to the right. I guess you found the Help button, since this is the help screen. Press the Config (configuration) button, have a look, and then return to Help. If sound is running you should see the Interrupts count increasing steadily. Some sound card information is shown, and some error counts. If anything prints in red, something is wrong. You must edit the configuration file to change the soundcard name or rate. There will be different sound card parameters for each name. See docs.html for more information, or if you can't get sound to run. If Interrupts are increasing, the Graph and Waterfall screen should work too.

Next press Graph to look at the graph screen, and then Help to return. You may need to run the "Ys" (Y scale) slide control on the right up or down to see the graph line. You should see a noise trace that changes randomly (without sound input). Then press Test1. This generates a test signal at 10 kHz, and you should see the spike on the graph. To tune to that signal, click the mouse on the graph near the spike. Hold the mouse button down and drag the red tuning line back and forth across the test signal. You should head a pure audio tone in your speakers. Use the "Vol" (Volume) slider on the left to change the volume.

If you press Graph again, you will activate the peak hold functions labeled "GraphP1" and "GraphP2". These will cause the graph to follow the peak signal, and decay back down at a slow rate. To control the rate, use the graph_peak_hold item in the config file.

Next press WFall to see the Waterfall screen, then Help to return. You can resize the Quisk window to get see more waterfall history. You will need to adjust "Ys" (Y scale) and "Yz" (Y zero) to get a colored display. You should see a strong 10 kHz signal. Press Test1 to turn the signal on and off. Watch it appear and disappear from the waterfall.

The top of the waterfall shows a small graph screen. You can grab the bar between the screens with your mouse and move it up and down to adjust the relative sizes. To adjust the scale and zero of this graph, hold down the Shift key while using the "Ys" and "Yz" sliders.

Next press Scope to see an oscilloscope screen. This is mainly useful for debugging.

Last press Filter and wait a few seconds. The response of the current filter is shown. Try changing filters by using the middle row of buttons on the right.

Tuning

On the Graph or Waterfall screens, you tune in a CW signal by clicking above the X axis directly on the signal. You tune in an SSB signal by clicking on the upper edge (lower sideband) or the lower edge (upper sideband). That is, you always click where the carrier goes. Make sure the proper mode is selected with the first row of buttons on the right. You can also click, hold down the mouse button and drag the tuning line. The speed of tuning is lowest close to the X axis, and increases as you move up. Try it.

If you click below the X axis, tuning will not jump to that frequency, but you can still hold the button and drag. That is useful for small adjustments. The mouse wheel will move the frequency up and down in small increments, and round the frequency to multiples of 50 Hertz.

If you right-click a signal, Quisk tunes to the signal as before, and also changes the VFO (if that is possible with your hardware) to move the signal to the center of the screen.

You can type a frequency into the entry box to the right of the frequency display, and hit Enter to jump to it. The frequency is in Hertz unless it has a decimal point, and then it is megahertz. The Up and Down buttons do not change the tuning, but will move the display up and down the band. Hold these buttons down to keep moving.

To really perform tuning, you need a VFO controlled by Quisk. I use a DDS VFO controlled by Ethernet. This DDS has a transmit and receive frequency, and a key signal to choose which to generate. Quisk (currently) assumes a single conversion to audio, as in the SoftRock-40 and FlexRadio 1000 receivers. If you have a fixed (crystal controlled) first conversion, use quisk_hardware_fixed.py and change self.vfo to the frequency in Hertz.

The frequency shown by the red tuning line and the frequency display window is always the transmit frequency. This equals the receive frequency unless Split is used (see below). The frequency display window will turn red to indicate sound capture (input ADC) overrun (clipping).

The RIT (receiver incremental tuning) button and slider can add a small offset to the receive frequency. Leave RIT off for SSB unless a station is off frequency a bit; then use RIT to tune him in while leaving your transmit frequency unchanged. When you select CW, the RIT must be turned on to provide an audio output, so Quisk automatically turns on RIT and sets it to plus or minus cwTone. The audio side tone (if a hardware key line is used) is set to the same. Just click CWL or CWU, tune the frequency by clicking exactly on the signal, and everything will work. The value of cwTone can be changed in your configuration file.

If the Split button is pressed, a second green tuning line is shown to indicate the receive frequency, and the receive frequency can be independently adjusted. The mouse controls the closest tuning line. To receive on the transmit frequency again, just turn Split off. The Split feature is used to work a DX station operating split, or it can be used to easily switch between two arbitrary receive frequencies.

Screen Sliders

There are three sliders on the right of the Quisk screen. The first two are labeled Ys and Yz, and they control the scale and zero of the screen in view. For the Graph screen and the Rx Filter screen they control the scale and zero of the Y axis. For the Waterfall screen they control the Waterfall color scale; and if the Shift key is down, they control the upper graph Y axis. For the Scope screen the Ys slider controls the Y axis scale, and the Yz slider does nothing. The sliders have no effect on other screens.

The Zo (zoom) slider expands the frequency scale (X axis) of the Graph and Waterfall screens so that narrow signals can be examined. Quisk operates normally when this slider is all the way down. As it is raised, the frequency is expanded around the tuning frequency. That is, the tuning frequency is moved to the center, and the frequency scale is expanded. It is still possible to tune Quisk as usual while this control is in use. For small frequency shifts, remember to use the right mouse button.

Other Controls

The sliders on the left control the main volume (Vol) and side tone volume (STo). Side tone is only active if you configure Quisk to operate as a transceiver, and change is_key_down.c to provide a key signal.

The two sliders on the right control the Y-axis scale (Ys) and zero point (Yz). On the graph screen, that means the range and zero of the graph. On the waterfall it means the gain and zero of the colors. Just try it.

The first row of buttons on the left selects the band. The "Audio" band is meant to set the VFO frequency to zero for use with a sound card and no hardware control. The "Time" band selects standard time signals. Pressing this button repeatedly selects different frequencies. The remaining buttons select the amateur bands. The 60 meter button can be pressed repeatedly to select the channels. Adding bands requires changes to quisk.py and more band plans in your configuration file.

The second and third row of buttons on the left select audio mute, AGC (automatic gain control), noise blanker and other features depending on your hardware. Right click the AGC button to adjust the threshold. Right click the Spot button (if present) to adjust the level.

The first row of buttons on the right selects the receive mode. The next row selects the filter to use. The filter bandwidths can be set in your config file. The right-most filter button bandwidth is adjustable; right-click it to adjust. The third row selects the screen to display: Graph, Waterfall, Scope, Config, Filter, or Help.

The S-meter displays the signal strength in S units and in dB. Zero dB is clipping, the same as on the graph screen. The S-meter uses the specified filter bandwidth to choose the exact number of FFT bins to square and average. That is, it displays true RMS based on the FFT bins, not on the post-filter audio. Note that for a noise floor on the graph of -110 dB the S-meter will read -93 dB (depending on some details). That is because the bandwith specified is much greater than the FFT bin width, and more noise is getting through. Find a flat noise frequency, change the filter bandwidth, and watch your S-meter measure the noise. The conversion from S-units to dB depends on your hardware. There are 6 dB per S-unit, and you can change self.correct_smeter in your configuration file (in S-units) to adjust to 50 microvolts for S9. If the correction depends on the band, you can make a band-dependent correction in your hardware file.

If you use the sound card for input, you may need to correct for small errors in the I and Q amplitude and phase. First change to the correct band, because corrections are saved for each band. Press the button on the config screen to bring up a correction screen. Then feed a test signal to your hardware (or use a strong available signal) and look at the signal image. Adjust the slider controls to reduce the image. The upper slider is the fine adjustment, and the lower is the coarse. You will need to adjust both amplitude and phase and they will interact. The amount of available adjustment range is controlled by your config file. When you have a final correction, it is a good idea to write it down. The correction point is saved based on the VFO frequency, and you will probably need two or three correction points per band.

Have fun with Quisk.