Chat on the Air with LinPsk

The original international electronic hobbyist community is ham radio. Here are the basics of the chat room without the room.
Running LinPsk for the First Time

The first time you run the program, a warning appears to alert you that no LinPsk.config file exists. This is a reminder that LinPsk should be configured first. The configuration can be tweaked or changed at a later stage, but an initial configuration must be set up. The configure dialog can be found under the menu title Settings→General Settings. Once selected, a window as shown in Figure 1 should appear.

Figure 1. From the LinPsk General Settings menu you can configure your callsign, time zone and the devices to use.

The first field contains the callsign, which is used in the macros. The offset between the local and utc time should be set as well, and it is defined as:

offset = utc - localtime .

To get the configuration dialog for the sound card, demo mode has to be deselected. The available input and output devices appear, and the one that is going to be used should be selected. The configuration dialog can be closed by clicking OK. The settings are not saved automatically for later use, so it is a good idea to save these settings with Save Settings in the Settings menu.

Tune your transceiver to 14.070.15MHz, upper sideband. If the 20-meter band is open, you should hear a variety of warbling tones from the radio speaker, each one representing a ham using PSK31. If everything is connected correctly, the screen should look like Figure 2 after clicking the RX button.

Figure 2. The main LinPsk window shows the available PSK31 signals in the lower left.

In the bottom left corner, the spectrum of the received signal is shown, and beneath that a translation of the spectrum values into colour values appears.

Due to the bandwidth of your transceiver, there may be a black gap on the left and right side of the spectrum. If a PSK signal is received, you should see one or more sharp peaks in the spectrum. If you click near the top of one of such a peak, and the options AFC and Wide under Rx Freq are selected, LinPsk tunes to the signal. In the circle inside the spectrum display, the phase of the received signal is represented.

This phase display can be used as indicator for quality of the received signal and as a tuning indicator at the same time. For a well-tuned BPSK signal, one sees only a vertical line. If the signal is slightly mistuned, the line is a bit buckled and rotated against the vertical.

As the AFC pulls the RX frequency to the center frequency of the PSK signal, the squelch display changes. The bar inside the squelch display increases and exceeds the threshold, and it changes colour from cyan to yellow. If this happens, letters appear in the receive window—you're now seeing the ongoing chat between two or more PSK31 users.

It is possible to listen to more than one QSO at the same time. To do this, one has to open another RX window from the file menu. As LinPsk supports other modes of operation, not only PSK, you are asked to select a mode for the new window. After that, you can click into the spectrum display at the desired frequency and watch.

The First QSO

After watching for a while, you might get curious and decide to answer a call. Be warned, though: you need a license to transmit on the ham bands.

Before transmitting, you should adjust the output volume carefully. PSK31 consumes little bandwidth, but if the output level is too high it can overdrive your transceiver, resulting in a lot of side loops that do not improve the coverage of the transmission. It's a good idea to use a dummy load when adjusting the output volume.

You should set the output volume in the General Settings menu to a low value. Pushing the TX button changes the labeling from TX to RX. The next time you push this button, the state changes to RX again.

Re-open the settings and watch the ALC of your transceiver. You should raise the output volume slowly until the ALC reacts, and then lower the volume some units again until the ALC settles down. Now the settings can be closed. Switch back to RX by pressing the TX button, and you are ready to answer calls.

You might tune to a running QSO and wait until it's over and one station calls CQ. Sending CQ means that the ham operating the station is interested in starting a new QSO with any other ham out there. Frequently, many QSOs are running at the same time. Which station will call CQ again first?

In such a case, open more RX windows from the File menu, tune each window to a QSO and activate the trigger in the upper-left corner. As the text to be triggered, enter CQ CQ. The trigger corresponds to the active RX window each time. Switch between the different RX windows and make another one active by clicking a tab in the right part of the window.

As soon as the trigger text is detected, LinPsk beeps and switches to the window in which the trigger text was detected. Whichever way you prefer, it now is time to answer the call.

Push TX and type the text you want to send into the TX window. Each character of the text transmitted is displayed in the RX window. When all text is transmitted, push RX again and wait for the reply. If the other station returns to your response, your first PSK31 QSO is going to start.


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