FT8 Screen

PSK (Phase Shift Keying)

Interesting PSK Videos

Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal (the carrier wave).
My last 10 PSK QSO's are with:
Call SignCountryBandDateTime (UTC)
W1AW/7United States20m12/13/201414:37:00
WA5LOUUnited States80m11/22/201403:35:00
W1AW/7United States20m11/08/201400:40:00
W1AW/7United States20m08/30/201423:44:00
W1AW/1United States30m07/27/201402:33:00
W1AW/4United States20m07/19/201413:23:00
W1AW/7United States15m03/09/201421:21:00
W1AW/6United States15m02/16/201421:43:00
N7WWLUnited States20m10/12/201217:48:00
Any digital modulation scheme uses a finite number of distinct signals to represent digital data. PSK uses a finite number of phases, each assigned a unique pattern of binary digits. Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data. This requires the receiver to be able to compare the phase of the received signal to a reference signal such a system is termed coherent (and referred to as CPSK).


Alternatively, instead of using the bit patterns to set the phase of the wave, it can instead be used to change it by a specified amount. The demodulator then determines the changes in the phase of the received signal rather than the phase itself. Since this scheme depends on the difference between successive phases, it is termed differential phase-shift keying (DPSK). DPSK can be significantly simpler to implement than ordinary PSK since there is no need for the demodulator to have a copy of the reference signal to determine the exact phase of the received signal (it is a non-coherent scheme). In exchange, it produces more erroneous demodulations. The exact requirements of the particular scenario under consideration determine which scheme is used.


Source: Wikipedia: http://en.wikipedia.org/wiki/Phase-shift_keying


One of the more popular software tools for working PSK is Ham Radio Deluxe and Digital Master 780. DM 780 makes it very easy to work PSK and to view multiple signals. Since PSK alls multiple QSO's to take place at once in the bandwidth of voice transmissions, PSK31 is a very efficient method for communications. Because the bandwidth used is very small, the amount of power needed for a transmission can also be small.


The image above is a screen capture of DM780 capturing a PSK31 QSO. The screen shows the typical PSK transmit and receive windows, but more importanlty, the "Waterfall" plot. The watefall plot is a very useful tool because it represents a graphical window that allows you visualize the station that are active and transmitting within a 31 kHz bandwidth. The stronger signals have the brighter colors, while the weaker signals will not be as bright. Using the waterfall graphic really is what makes PSK31 operation easy to tune and enjoyable to work.


All that is really needed to run PSK31 is an HF radio, a computer with a sound card, an interface that connects to the PC and the transceiver such as a RigBlaster or a homebrewed audio coupled solution and Ham Radio Deluxe.


Another neat feature built into DM-780 for PSK31 is the 'Super Browser'. A picture of the Super Browser is on the right. It allows you to see all on-going conversations and calls, and easily connect or join in by simply clicking the red test string of the station you wish to contact. It works by simply turning the waterfall up on it's side, and decoding each individual data stream...all at once! I find this very useful for quickly spotting a station that I might want to call CQ to.


There is a great tool available for looking for PSK contacts and that is from Hamspots.net. They offer a great tool that allows you to see PSK spots that have been found by other operators.


© 2019 , Jonathan Tucker N8MDP. All Rights Reserved.