AFSK generator?

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AFSK generator?

Permanent link to this post Posted by weldo5 » Mon Nov 18, 2013 9:36 pm

9/14/16 edit: (trying to find a good place to put this).., Since Nyquist and audacity are known for its wonderful waveform generators such as the DTMF, tone, as well has the handy dandy Nyquist prompt, was just wondering if anyone could give some programming via an Audio frequency shift keying (such as used in packet radio and such)

there are any options of doing so, but the two below are the most common ways to do it.
1st option:
1. with varying frequency boxes for each of the binary 1s and 0s (mark and spaces),
2. The frequencies can have various cycles per shift
3. and the 1s and 0s can be put into an endless scrolling text box, entering as many as you want which can generate the AFSK tones at those desired frequencies.
4. There should also be an option of gaussian filtering, which can make transistions smoother between shifts, and remove harmonics.

2nd option:
Or, since AFSK is generated traditonally via a binary pulse coded wave, modulated a bit, with some amplitude cutting or whatever the causes, can also generate AFSK tones. This means the resulting waveform is modulated via a modem, making it much easier.

ill try to provide pictures for option 1, as long as my computer can co-operate with displaying them in these forums.

Finally, since I seem all over the place, i'm trying to be as directive as I can on this so it makes sense.

NOTE: I am using LISP for this one, not SAL.
Last edited by weldo5 on Wed Sep 14, 2016 10:46 am, edited 4 times in total.
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Re: FSK generator?

Permanent link to this post Posted by steve » Mon Nov 18, 2013 9:39 pm

Audacity has a DTMF generator included: http://manual.audacityteam.org/o/man/ge ... .html#dtmf
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Re: FSK generator?

Permanent link to this post Posted by weldo5 » Mon Nov 18, 2013 9:48 pm

DTMF I know that. Ive used that plenty of times for experimentation. It actually creates a similar spectrum even though the frequencies are different, and there are less peaks throughout the higher harmonics.
Last edited by weldo5 on Sun Aug 14, 2016 6:23 pm, edited 1 time in total.
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Re: FSK generator?

Permanent link to this post Posted by steve » Mon Nov 18, 2013 10:18 pm

In case you've not noticed, I know little about FSK ;)
One of these Nyquist generators could be a good place to start: http://wiki.audacityteam.org/wiki/Nyqui ... 8random.29
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Re: AFSK generator?

Permanent link to this post Posted by weldo5 » Mon Nov 18, 2013 11:01 pm

AFSK stands for audio frequency shift keying, which uses audio tones at two different frequencies to be sent via a radio link for decoding as a message. Think of packet radio on 144.39 MHz in the US. That type of modulation is Bell 202 AFSK 1200 baud.

There are many types that are used throughout all the RF bands, all at different baud rates and shifts.

There's also MFSK (multiple frequency, similar to DTMF you were talking about)

The baud rate is how many bits per second that the resulting waveform is transmitting at.

Like I've said in the beginning post, (last edited 8/14/2016) ther are many options for generating these types. (which I know youve listed below already).
Last edited by weldo5 on Sun Aug 14, 2016 6:29 pm, edited 1 time in total.
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Re: FSK generator?

Permanent link to this post Posted by weldo5 » Wed May 18, 2016 12:12 am

The DTMF randomizer is also very cool, sometimes even randomized dtmf can bring up some odd numbers or words depending on which decoder you have, (not sure which ones would work) but it might be cool to recognize it.
Last edited by weldo5 on Sun Aug 14, 2016 6:46 pm, edited 1 time in total.
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Re: FSK generator?

Permanent link to this post Posted by steve » Wed May 18, 2016 11:15 am

It sounds like it should be possible (though arduous) to generate the type of tones you require using the built-in functions in Audacity (tone generator, speed change effect, etc.)
If that is possible, then I'd expect that it could be done in a Nyquist script. Can it be done 'manually'? If so, could you give step by step instructions, including a short example WAV file to illustrate the end result, then I'll know what the Nyquist script needs to do.
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Re: FSK generator?

Permanent link to this post Posted by weldo5 » Wed May 18, 2016 3:03 pm

8/14/2016: It is very hard to do traditionally, but there are simple ways of doing it tradtionally through the arduous way. One of them is, and is usually done by me

1. Type any binary number format in Some text document either in notepad or some other word program
2. open audacity
3. window audacity and stretch it to be narrow horizontally (this would make it be a narrow horizontal window)
4. Stretch the text document that was just filled with the numbers, stretching it to be a reasonable width, narrow it like the audacity window
5. Look carefully at the beginning binary number
6. Generate an audio tone for the binary 1 or 0, at a reasonable SAMPLE amount, use samples because that way it will be more efficient at higher baud rates, (ex, (1200 baud)for a 48000 hz binary 1, should be a 1200 hz sine wave at 40 samples), and a binary 0, (66 samples for one binary 0). Just make sure its a reasonable sample rate, and a sample amount to match an entire cycle.
7. it can be very stressful at first, but it could get a bit faster afterwords, it might take even longer just for the string of binary numbers to completely be "encoded", or generated the right way.
Last edited by weldo5 on Sun Aug 14, 2016 6:46 pm, edited 2 times in total.
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Re: FSK generator?

Permanent link to this post Posted by steve » Wed May 18, 2016 5:58 pm

weldo5 wrote:Yes, I have tried that before with the manual doing, but it is a lot of hard work.

So what are the steps?

weldo5 wrote:Research FSK, click on the Wikipedia for the definition and the wav file should be there

I'm willing to help you with Nyquist coding, but I don't have the time or inclination to do the "legwork" ;)
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Re: AFSK generator?

Permanent link to this post Posted by weldo5 » Sun Aug 14, 2016 7:13 pm

POST NEEDS DELETING...........................

here's one of the ways ive been doing it, its simple but take longer: Image
Last edited by weldo5 on Thu Oct 06, 2016 6:16 pm, edited 1 time in total.
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