Talk:Frequency-shift keying
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[edit] == 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)
[edit] 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. ==
[edit] 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 ΔF is
where 1 / T is the bit rate, ΔF is the frequency shift and the modulation index η = 0.5 for MSK. Hence, the difference between the higher and lower frequency is
--Drizzd 13:13, 9 July 2006 (UTC)
- Indeed. I've altered this. Oli Filth 14:52, 21 August 2006 (UTC)
[edit] 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 (RA+RB) up to 2/3Vcc. Then it discharges through RB up to 1/3Vcc. This exponential charging-discharging continues as long as input is logic 1.
Mark Frequency == 1070 Hz
When input is logic 0, the PNP transistor is on (saturated), connecting RC across RA. Hence frequency obtained is:
Space frequency == 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)
[edit] 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)
