Talk:PSK31

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Bandwidth[edit]

The image doesn't show PSK31 bandwidth. LeighKlotz

Would a waterfall display from fldigi help? --ssd (talk) 06:01, 4 February 2013 (UTC)[reply]


I also have a question about bandwidth. If all that is used is a percentage (percentage bandwidth) of the total bandwidth, I would like to know if the radio still spits out the total bandwidth, or that percentage. I have a feeling that it's the former, but I would like to know for sure, and I have asked for a citation where it says it "concentrates" the RF energy. 86.172.56.120 (talk) 13:20, 10 July 2017 (UTC)[reply]

Sound Sample[edit]

There is no sound sample. LeighKlotz

I can't decode the provided QPSK-31 sound sample, but have no problems with the QPSK-31 sample at http://www.w1hkj.com/modes/index.htm -> BPSK -> QPSK-31 -> Sound, where I decode "umped over the lazy brow" no problem. Using the same decode method on the sample here I get only garbage characters. (I am using fldigi software, but it shouldn't matter.) Can someone else either verify my results or that the sample here does decode to "Welcome to Wikipedia, the free encyclopedia that anyone can edit." as stated? WA6NDR Rick314 (talk) 02:56, 15 December 2019 (UTC)[reply]

AM Modulation[edit]

PSK is not produced by modulating the RF carrier directly; that would produce AM. LeighKlotz

I believe PSK is usually FM modulated, although I think it can be AM modulated. This is true for most data radio modulation modes, even standard TV signals. Esentially, the data is modulated to an audio frequency signal, which is in turn modulated, usually with AM or FM. --ssd 15:40, 24 December 2005 (UTC)[reply]

PSK31 uses Single sideband modulation - while one could use FM or AM to send the audio generated by a PSK program, the resulting signal would NOT be a PSK31 waveform, and would NOT have the narrow bandwidth of PSK31. In effect, the computer + the SSB transmitter form a Software defined radio with the first local oscillator being the numerically-controlled oscillator in the PSK software and the first intermediate frequency being the audio signal out of the soundcard. N0YKG 19:54, 10 April 2006 (UTC)[reply]

Emission Code[edit]

Edits of 8/9 Oct 11[edit]

Good...we are finally getting somewhere. I made a few changes, then Albany45/AA6E made some better ones (nice waveform picture). Can we now finally make that one last change to nail the myth of PSK31 being anything to do with 'shifting the phase of the carrier'. All this arose because of one sentance in Peter M's article, where he was actually talking about somebody else's earlier idea. PSK is just a sound...a series of 'beeps' just like morse, but using a new machine-readable alphabet. Any change (i.e. key-up or key-down) is a 'zero', and no change (i.e. a 'dah') is a 'one'. This is in no way meant to denegrate the ingenuity of PSK31, its beauty lies in its simplicity, and the adaptation of a very old idea (morse code) for new technology. (G6CSL) 81.158.227.166 (talk) 13:12, 9 October 2011 (UTC)[reply]

The image of the waveform is great and shows the 180 phase shift in the audio (not in the carrier). Since it is a vector diagram, it might be better as a SVG, however. -- Autopilot (talk) 19:15, 9 October 2011 (UTC)[reply]
I don't think I agree about audio vs carrier phase shift, or else there is a semantics problem. There is no "audio" as such. There is a modulation waveform that is effectively multiplying the carrier. (And the carrier can be in the audio range, as on your sound card, or in the RF, as it goes to the antenna. (No difference really, except frequency.) In a zero cell, the modulation goes negative, and the modulated signal flips 180 deg. "in the carrier" if you like. This is shown in the figure. If you look closely, you will see that the carrier phase after a zero/null is 180 deg. opposite from the phase before. The figure is a screenshot from LibreOffice Calc, which does not offer SVG export!--Albany45 (talk) 19:57, 9 October 2011 (UTC)[reply]

You're right that "audio" is not the right technical term for the baseband signal, although it is how we hear PSK31 after it has been demodulated from the SSB RF signal and how File:PSK31_sample.ogg presents it. The plot does show the 180 phase shift quite clearly, as well as the cosine ramped amplitude to reduce the bandwidth of the phase shift. For SVG creation, you might try the free software program inkscape. -- Autopilot (talk) 20:18, 9 October 2011 (UTC)[reply]
Not to be too fussy, but I would not say that the audio recording is demodulated. It is identical to the RF signal, except it is frequency shifted down to the audio range. Demodulation (detection) is what happens when you take that signal and convert it back to 1's and 0's. The situation is similar for SSB voice, too. The audio receiver output is identical to the RF, except for frequency translation. "Detection" happens in your head. FM definitely requires detection before you can get audio back. My 2 cents!--Albany45 (talk) 01:58, 10 October 2011 (UTC)[reply]

OK, it's not a big issue really, and in the spirit of Wiki and ham radio we will agree to differ.

Just try one thing for me: For a moment...forget that you are a radio ham. Put your radio into a box and bury it at the bottom of your garden. Then cross-connect two computers' soundcards together. Out-to-in, and in-to-out. Send PSK31 back-and-too between the two computers for a while, then dig the radio up and ask yourself if it has been 'shifting its phase' :-) Like I said, PSK31 is a very clever system of audio 'beeps' which you may or may not choose to feed into a radio microphone socket. It works just as well over a telephone, or even through air, and if you are sending on SSB the carrier (phase shifted or not) never even gets transmitted in the first place, unless there is something seriously wrong with your rig...just the beeps!. It's all very clever. Best Wishes G6CSL 81.158.227.166 (talk) 17:42, 10 October 2011 (UTC)[reply]

PSK31 modulation is achieved by shifting the phase of a signal carrier. There is a carrier wave present in all PSK31 exchanges, irregardless of the medium (EG: Radio, air (acoustic), telephone, a direct wire between to computers, etc). The tone PSK31 software generates, is the carrier, and the "beeps" are a result of phase shifting that carrier.
Now, I know what I just wrote above will likely cause some confusion, in addition to confusion I suspect already exists, so I'm going to attempt to clear up what I think are multiple points of confusion:
First, a carrier is a waveform (usually sinusoidal) that is modulated (modified) for the purpose of conveying information. (This was largely taken from carrier wave.) A PSK31 signal falls under the definition of a modulated carrier. The signal, which comes out of a sound-card, is a sine-wave which is either shifted or not shifted in its phase, at a moment in time, to represent a either a 0 or 1 respectively.
Second, carriers are not unique to radio communications, but rather they may be utilized in any form of electronic communication, including acoustical and wire-line. In non-radio systems, carriers may be used to carry multiple, communication channels on the same medium (EG: Multiplexing). A classic example of this is cable TV (and the lessor known cable FM), which deliver each channel on a separate carrier, via one cable. In addition, the first historical example involved experiments in operating multiple telegraph signals on a single telegraph line. This first use of carriers predates radio experimentation and led Alexander Graham Bell to the development of the telephone.
Third, a modulated carrier may be used in turn to modulate yet another carrier. An example of this would be to feed a PSK31 signal into an FM transmitter. In this case, the PSK31 signal would be a subcarrier of the fundamental, FM carrier. Before the PSK31 could be decoded, one would first have to demodulate the FM carrier to extract the PSK31 subcarrier. Several common examples of subcarrier exist in FM broadcasting: FM stereo, Radio Data System, Subsidiary Communications Authority, In-band on-channel, etc
Fourth, where the core of confusion likely lies is that PSK31 is most often used in conjunction with a SSB transmitter. In SSB, the AM carrier is suppressed from transmission, leaving only its modulating signal. This has the effect that any "SSB subcarrier" becomes the fundamental carrier of the emission. SSB transmitters, in large part, are functionally equivalent to transverters (as well as linear transponders). A SSB transmitter takes low frequency signals, in what is often referred to as the audio frequency range, and shifts them up to a much higher frequency range. Any single, "audio" tone, fed into a SSB transmitter, will produce a continuous wave emission. Likewise, if a Phase-shift keyed AF signal is fed into a SSB transmitter, a PSK RF signal will be transmitted.
I hope this clears things up.
–Sparkgap (talk) 20:37, 11 October 2011 (UTC)[reply]

Well done sir...even I understood that :-) Yes, the audio tone is the carrier, in that it 'carries' the information (not to be confused with the 'other' carrier from your rig). Like with a smoke signal...the smoke is the carrier, and what you do with it forms the message. In your soundcard, positive or negative both produce a 'tone', and the instant of zero-volts as you cross-over (when you switch polarity) produces a short silence (well almost). The program listens every 32 milliseconds to see 'what is going on' at that instant, relative to what happened 32 milliseconds ago. Beep-then-beep is '1', and beep-then-silence (or silence-then-beep) is '0'. Beep-silence-beep-silence-beep (i.e. two shifts) is '00', which means that one letter has ended and a new one has begun. So if (god forbid) one were to be pedantic, then it's really 'Polarity Shift Keying'...but let's not go there :-) Regards, G6CSL 217.43.235.177 (talk) 18:35, 13 October 2011 (UTC)[reply]

Question[edit]

Which software gives the possibility of reading up to ten signals in parallel? DJ4PG --Hans Eo (talk) 15:32, 12 November 2012 (UTC)[reply]

Wikipedia is not a ham radio forum. You should find a better place to ask for help or suggestions! But you could look at fldigi :-) --Albany45 (talk) 22:14, 12 November 2012 (UTC)[reply]

Humm I am working on the article about psk in the german wiki. ok? Thanks for the info. --Hans Eo (talk) 20:13, 13 November 2012 (UTC)[reply]

Both fldigi and hamradio delux can receive multiple simultaneous signals, but it isn't limited to 10 specifically. --ssd (talk) 16:01, 14 April 2013 (UTC)[reply]

Resistance to interference[edit]

The article mentions that psk31 is resistant to interference and bad propagation but does not say why. This is typical of narrow band digital modes because a) the entire power of the transmitter is focused into the narrow bandwidth (i.e., 31.5 hz instead of 3khz for the same power) and b) the digital data in the analog signal is expected to look a certain way and can be reconstructed even when mixed with some tolerable amount of analog noise. Anyway, I've worded this poorly, and can't figure out how to fit it into the current article flow, and I'm not even sure it is appropriate for this article, as it would apply equally well to nearly all digital modes including CW. --ssd (talk) 06:06, 4 February 2013 (UTC)[reply]

Well it's your Wikipedia too. There's nothing wrong with anything that you say. PSK concentrates the available transmit power into a very narrow bandwidth, and the fact that the data arrives 'on time' - so the software knows exactly when to listen - makes it rather 'coherent'. There's nothing mystical about PSK, it's just like coherent morse. Have a go. G6CSL 86.132.212.124 (talk) 10:44, 10 February 2013 (UTC)[reply]
It's fitting the words into the flow of the article I'm not sure about, not the actual content I'm worried about.  :) I leave the above comment here so that someone (maybe me) might improve the article with those ideas some day. --ssd (talk) 05:43, 13 February 2013 (UTC)[reply]
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