Talk:Frequency-shift keying

Can someone with knowledge of DFSK add information on that to this page? —Preceding unsigned comment added by 128.253.139.181 (talk) 01:28, 1 April 2010 (UTC)

FFSK?

oh A type of FSK that I have used for signalling in the past consists of a '1' being represented by a single cycle of a frequency f, and a '0' by 1.5 cycles of frequency f + f/2, phase continuous (typical frequencies would be 1200Hz and 1800Hz). It's a very neat and compact scheme, very easy to synthesise, with every bit period being equal, and very easy to decode, counting zero-crossings. I always though this was called FFSK, with the extra F standing for 'Fast', but currently there is no article about this. Is it perhaps known by another name? Graham 11:46, 8 February 2006 (UTC)

Yes. FFSK is equivalent to MSK. Oli Filth 14:57, 21 August 2006 (UTC)

No. FFSK is equivalent to what the fine article calls "Audio FSK" Ok, to be fair, there is a problem here that the same term is used to mean different things. but could we try to make this more clear in tfa? (sorry at the moment i have no clear idea how). — Preceding unsigned comment added by 194.209.214.225 (talk) 13:56, 18 August 2011 (UTC)

ASK gets all the love :(

I'd like to see this article brought up to the quality of Amplitude-shift_keying. I'm not an EE, but I do have Stallings open here, but the amount of actual detail is pretty thin. I don't have the background to elaborate or generate the math or diagrams necessary. ==

MSK

I think the article is wrong about the bit rate to frequency shift ratio. The difference between the higher and lower frequency (i.e., twice the frequency shift) is equal to half the bit rate.

The formula for the frequency shift $\Delta F$ is

$\eta =2\,\Delta F\,T\;,$

where $1/T$ is the bit rate, $\Delta F$ is the frequency shift and the modulation index $\eta =0.5$ for MSK. Hence, the difference between the higher and lower frequency is

$2\,\Delta F=0.5\,{\frac {1}{T}}\;.$--Drizzd 13:13, 9 July 2006 (UTC)

Indeed. I've altered this. Oli Filth 14:52, 21 August 2006 (UTC)

Implementation Example - moved from page

Need a diagram for this to be useful in the article. I may do this myself if I have time.

The greatest single reason for the widespread use of FSK is its simple implementation. All that is required is an oscillator whose frequency can be switched between two preset frequencies. This can be easily achieved using the 555 timer IC. As the carrier signal is shifted between two preset frequencies, hence this technique of signal modulation got the name FSK.

The frequency corresponding to logic 0 and 1 are called 'space' and 'mark' frequency respectively. The FSK generator is constructed using a 555-timer in astable mode, with its frequency controlled by the state of a PNP transistor. 150Hz is the standard frequency at which data input can be transmitted.

When input is logic 1, the transistor is off. The capacitor then charges through (R_A+R_B) up to 2/3Vcc. Then it discharges through R_B up to 1/3Vcc. This exponential charging-discharging continues as long as input is logic 1.

 Mark Frequency = $1.44 \over {Ra+Rb}$ = 1070 Hz

When input is logic 0, the PNP transistor is on (saturated), connecting R_C across R_A. Hence frequency obtained is:

 Space frequency = $1.44 \over {Ra||Rc+Rb}$ = 1270 Hz

Hence by proper selection of resistors, the mark and space frequencies can be selected. The difference between 1070 and 1270 Hz is of 200 Hz and is called 'frequency drift'.

—Preceding unsigned comment added by Ktims (talk • contribs) 05:52 24 OCT 06

No problem. Btw, which program do u use for makin ccts, or are u on bitmap too? Xcentaur 07:53, 24 October 2006 (UTC)

I normally use Eagle (program) because the free version is quite good, but it doesn't produce output that's appropriate for Wiki without some editing. You could try Dia as well, I've used it a bit and it's not very useful for circuit design but it produces nice output. And there's always [1] which is great for simple circuits. --Ktims 08:50, 24 October 2006 (UTC)

Ah. Had a lot of ccts that I wanted to add but dint know how. This helps a lot. Thanks. Xcentaur 09:28, 24 October 2006 (UTC)

Incremental frequency keying?

A description of "incremental frequency keying" has recently been added. However, a Google search reveals only 39 hits, so I'm not sure it's particularly notable or widely used. Any thoughts? Oli Filth^(talk) 01:01, 7 December 2007 (UTC)

I see that Google gives 313 hits for "differential frequency shift keying". Is that notable enough?

I agree that IFK is not notable enough to give an article of its own. However, I've been told that "The particular topics and facts within an article are not each required to meet the standards of the notability guidelines." -- WP:NNC. --75.19.73.101 (talk) 06:48, 13 December 2007 (UTC)

acoustic fsk

Is not yodeling a form of fsk? SyntheticET (talk) 04:00, 14 August 2008 (UTC)

Continuous Phase Frequency-Shift Keying

As both FSK and Continuous-phase frequency-shift keying (CPFSK) are a special form of frequency modulation, shouldn't CPFSK be mentioned in this article? What about 4-level Continuous FM (C4FM) - is this the same as CPFSK? --Dmitry _{(talk•contibs)} 09:43, 26 March 2012 (UTC)

I agree, so I added a brief mention of CPFSK and C4FM to this article. --DavidCary (talk) 18:18, 28 January 2015 (UTC)

Added References and Moved MSK

I have added some references for modem implementations, added markers for necessary citations and moved the MSK stuff to the corresponding subpage. — Preceding unsigned comment added by 2A4Fh56OSA (talk • contribs) 19:03, 29 December 2012 (UTC)

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Weitbrecht Modem

Three questions: 1) What kind of FSK is used in a Weitbrecht Modem as used in the Telecommunication Devices by Deaf people, known by the abbreviation TTY or TDD? 2) When was the first FSK introduced for telephonic communication? 3) Why did no telephone company develop a device similar to Weitnrecht Modem already in the late 19th or early 20th century to enable deaf people to use telephone? 74.104.144.152 (talk) 15:45, 13 July 2019 (UTC) Hartmut Teuber, 13 July 2019, 11:40 am EST

The radioteletype article mentions that in WWII radioteletypewriters, "The transmitting part of the modem converts the digital signal transmitted by the teleprinter or tape reader to one or the other of a pair of audio frequency tones, traditionally 2295/2125 Hz (US) or 2125/1955 Hz (Europe)."

I speculate that perhaps Marsters, Weitbrecht and Saks used surplus WWII radioteletypewriters originally set up for those frequencies. In equipment of that era, it would have been fairly easy to change those frequencies, but I further speculate that perhaps Marsters, Weitbrecht and Saks kept the same frequencies for their telecommunications device for the deaf § APCOM acoustic coupler or MODEM device.

If so,

• 1) it uses binary FSK in the audio range (audio FSK).
• 2). I suspect the first FSK for telephonic communication was the radioteletypes. Communicating over radio requires some sort of modulation, which was unnecessary for the hard-wired connections used for earlier teletypes.
• 3). I suspect they didn't see the need for modems. If you wanted to transmit text, you could use the standard unmodulated high/low signals of teletypes that have worked since before 1897. (On, of course, the leased lines that worked by hard-connecting physical wires that were much more expensive than voice-grade lines -- see modem).

--DavidCary (talk) 03:04, 29 January 2022 (UTC)

Apparently at least one of my guesses was wrong: The teleprinter article mentions the U.S. Patent 3,507,997 "Frequency-Shift Teletypewriter" filed 1966 by Robert H Weitbrecht. That patent mentions mark and space frequencies of 1400 c.p.s. and 1800 c.p.s. respectively. (I.e., 1400/1800 Hz.). --DavidCary (talk) 01:21, 2 February 2022 (UTC)

low deviation modulation

What is the "LDM-2 low deviation modulation" mentioned in the NT (cassette) article? Should this "frequency-shift keying" article mention it? --DavidCary (talk) 03:04, 29 January 2022 (UTC)