What Technique Is Used to Minimize the Bandwidth Requirements of a Psk31 Signal?

PSK31 or "Phase Shift Keying, 31 Baud" is a digital, used primarily in the amateur radio field to conduct real-time informal text conversation between amateur radio operators. Vernacular usage of the term PSK31 in amateur radio near often implies the use of binary stage shift keying which is the mode BPSK31. By not assigning the X in X PSK31, BPSK31 is implied.

History

PSK31 was developed by English language amateur radio operator Peter Martinez (G3PLX) and introduced to the wider amateur radio community in December 1998. Martinez initially called his creation "varicode", considering it uses variable length encodings (Huffman codes) to stand for characters.

PSK31 was enthusiastically received, and has since quickly spread into worldwide utilise. Due to the efficiency of the fashion, information technology has become especially popular with operators whose circumstances do not permit the erection of large antenna systems and/or the use of high power.

Because the mode is seen as such an effective ways to communication via PC, its audition has grown similar wildfire in the years since its release. and lent a new tone to the on-air conduct of digital communications.

Use and implementation

Very little equipment – in addition to a standard radio transceiver – is required to apply PSK31. Ordinarily an quondam PC and a few cables will suffice; the software is both free to download and runs happily on old, deadening computers from the early Pentium era or even before.

The operator typically uses a single sideband transceiver continued to the sound card of the PC. When the operator enters a message for transmission, the software produces an audio tone, which sounds to the human being ear like a continuous whistle with a slight warble. This is and then fed through either a microphone jack (using an intermediate resistor to reduce the sound card's output ability to microphone levels) or an auxiliary connection into the transceiver, where it is transmitted.

From the perspective of the transmitter, this amounts to niggling more than somebody whistling into the microphone. Withal, the software speedily shifts phase of the audio signal betwixt 2 states (hence "phase-shift keying"), forming the varicode. These phase shifts serve the same role as the 2 tones used in traditional RTTY and similar systems.

To decode PSK31, the received audio whistle from the transceiver'southward headphone output is fed into the sound card'due south audio input, and the software decodes information technology. The software also includes a user interface on the PC, which is used to display the decoded text and manage the software configuration.

The apply of PSK31 does not crave sectional utilize of a dedicated estimator. When not running the PSK31 software, the computer tin still be used exactly as before. Once set-up to run PSK31, the aforementioned computer and cables can then also be used to explore other interesting modes such as RTTY, Hellschreiber, Olivia MFSK etc, and perform useful tasks such as automatically monitoring radio propagation beacons.

Resistance to interference

PSK31 can often overcome interference and poor propagation conditions in situations where voice or other data methods of advice fail. However, PSK31 was only designed for leisure use by amateurs, and due to its relatively boring speed and minimal or no error control, is not intended for the manual of large blocks of information or text, or critical data requiring high amnesty from errors.

PSK31 works well with propagation paths that preserve phase, and can exist adversely affected by those that do not, such equally transpolar paths, where auroral influence can disrupt the signal phase continuity.

Some software supports PSK10 and PSK05 variants, running at 10 baud and 5 baud, respectively. These slower speeds sacrifice throughput to provide even greater resistance to noise and other interference.

Technical information

PSK31 is a half-duplex mode of communication. Thus only 1 participant in the chat tin can transmit at a time.

Technically, varicode is the encoding method, and PSK31 the transmitting method. Varicode was designed so that, as in Morse code, the more frequently occurring characters would take shorter encodings, while rarer characters used longer encodings.

PSK31'south bandwidth of 31.25 Hz was chosen because a normal typing speed of virtually 50 words per minute requires a chip rate of about 32 $.25 per second, and specifically considering 31.25 Hz could easily exist derived from the 8 kHz sample rate used in many DSP systems, including those used in the computer sound cards usually used for PSK31 functioning (31.25 Hz is 8 kHz divided by 256, and so can be derived from 8 kHz by halving the frequency viii times).

PSK31 ordinarily uses no fault control, but an allied mode, QPSK31, uses four phases to provide a degree of forrad error correction.

Spectrum efficiency compared to other modes

PSK31'southward efficiency and narrow bandwidth make it highly suitable for depression-power and crowded-band functioning. PSK31 contacts can be conducted at less than 100Hz separation, so with disciplined operation at least twenty simultaneous PSK31 contacts can be carried out side-by-side in the bandwidth required for just one SSB voice contact.

Common Frequencies

The following apprentice radio frequencies are normally used for transmitting and receiving PSK31 signals.

PSK31 Frequencies

Frequency	Amateur Ring
ane.838.15 MHz	160 meters
3.580.xv MHz	80 meters
7.035 MHz	twoscore meters (regions 1 and 3)
*7.080.xv MHz	40 meters (region 2)
ten.142.15 MHz	30 meters
xiv.070.15 MHz	20 meters
18.100.15 MHz	17 meters
*21.080.15 MHz	15 meters
24.920.15 MHz	12 meters
28.120.15 MHz	x meters
50.290 MHz	6 meters

• Current usage every bit of 2010, based on ascertainment, is centered on seven,070.15 and 21,070.15.

There is no authoritative list as the frequencies are adamant by common convention.

References

• Peter Martinez. PSK31: A new radio-teletype mode with a traditional philosophy. http://det.bi.ehu.es/~jtpjatae/pdf/p31g3plx.pdf
• http://members.cox.internet/jrehak/PSK31.htm
• http://www.facebook.com/pages/digitalradio/123270301037522
• http://www.obriensweb.com/digispotter.html

External links

• PSK31: Has RTTY's Replacement Arrived? Article past Steve Ford, WB8IMY, introducing PSK31
• The Official PSK31 Page
• ARRL PSK31 Info Page
• How to operate PSK31 | PSK31 Guide
• PSK31 Frequencies A listing of frequencies for PSK31 operation.

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Source: https://lms.onnocenter.or.id/wiki/index.php/Teknologi_PSK31

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