Electricman2K5
New Member
Im trying to use a Lm567 tone decoder as a PLL to demodulate 5Khz FM
to test im using the formula fo= 1/1.1RC ive used a 10 K variable resistor set to about 5.5K and a 33nF cap giving fo as 5.509Kz. Im inputting a 5khz signal through pin 3. I think its working the LED flashes but it seems that it works for a very large range of frequencies input into it the LED stays on.
Seems like a large bandwidth using B/W = 1070sqrt(Vin/foc2) - I increased the capacitance it doesn't really seem to work too accurately though.
Furthermore the main problem is when I change the input (signal voltage up) say above 0.5V the LED lights at frequencies well above the cutt off. I need to demodulate FM with the system so its a problem.
Can anyone help/suggest some stable values ?????????
to test im using the formula fo= 1/1.1RC ive used a 10 K variable resistor set to about 5.5K and a 33nF cap giving fo as 5.509Kz. Im inputting a 5khz signal through pin 3. I think its working the LED flashes but it seems that it works for a very large range of frequencies input into it the LED stays on.
Seems like a large bandwidth using B/W = 1070sqrt(Vin/foc2) - I increased the capacitance it doesn't really seem to work too accurately though.
Furthermore the main problem is when I change the input (signal voltage up) say above 0.5V the LED lights at frequencies well above the cutt off. I need to demodulate FM with the system so its a problem.
Can anyone help/suggest some stable values ?????????
