fsk transmitter - Page 2 - Electronic Circuits Projects Diagrams Free

**Nigel Goodwin** · 26th February 2004, 06:27 AM

Quote:

Originally Posted by mugzzzzy

No infra red..gotta be wireless....and once again its not illegal what i m doing...its for educational purposes...and the power of my antenna wont effect the information of who ever is using this frequency

Infra red is wireless as well!.

And once again, illegally transmitting using a band you're not licensed to use is still illegal, if it's for educational purposes it makes no difference at all. I'm astonished if your teacher has suggested you do this!, particularly as the teacher, the school, as well as yourself, could all be liable to prosecution.

mugzzzzy · 26th February 2004, 06:53 AM

hi,

its all good ,thanks to worry for me, 10Mhz is a citizen free band ... but in the frequency table....i didnt see band made only for school teaching telecommunication or something like that

;-)

Roff · 26th February 2004, 03:32 PM

Quote:

Originally Posted by jem

Once a PLL has "locked" on a signal, it will track the signal provided there are nondiscontinuous phase changes, and the signal remains within its tracking range. In the worst of cases, a PLL will take quite some time to lock on a signal even though the signal frequency is within its capture range depending on the phase of its internal VCO at the time in relation to the phase of the input signal (also on the characteristics of the LPF). The result of this delay is that the detected pulse width is smaller than the actual pulse that was sent, by a random (but bounded) amount. The bottom line is the data rate suffers. It is quite possible to send a tone burst, and detect it by using a tone detector such as the 567, but if the tone burst duration is small, sometimes (worst case about 14 cycles) the 567 will not detect it.
Anyway, this is at least my understanding of it. I haven't been a commications engineer since four jobs, and about 16 years, ago!

Jem

You're in about the same boat I'm in. I used to design PLLs for digital video time base correctors, but it has been 16 years since I did that. I can assure you that a PLL can easily track a step in phase (phase discontinuity). I'm not sure if this is true of very narrow bandwidth PLLs, but for the ones I designed, that is exactly what they had to do.

jem · 27th February 2004, 02:20 AM

Were there no glitches in the LPF output with a step change in phase? It would seem that the phase detector will output something as the VCO is slowly brought back in phase with the incoming signal. As I remember, we used phase coherent FSK and PLL for mark/space frequencies that were close (small shift), and filters for larger shifts. Then again, it was quite a while back, and also my first job out of school.

BTW: Are you the Ron H. who used to work at 499 Park Ave.? From your posts, you would fit perfectly. If that is the case, then we know each other!

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26th February 2004, 06:53 AM	(permalink)
mugzzzzy	hi, its all good ,thanks to worry for me, 10Mhz is a citizen free band ... but in the frequency table....i didnt see band made only for school teaching telecommunication or something like that ;-)

27th February 2004, 02:20 AM	(permalink)
jem	Were there no glitches in the LPF output with a step change in phase? It would seem that the phase detector will output something as the VCO is slowly brought back in phase with the incoming signal. As I remember, we used phase coherent FSK and PLL for mark/space frequencies that were close (small shift), and filters for larger shifts. Then again, it was quite a while back, and also my first job out of school. BTW: Are you the Ron H. who used to work at 499 Park Ave.? From your posts, you would fit perfectly. If that is the case, then we know each other!