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Re: NE567 tone detector (help)



Hi Bob.
 
I've just rummaged through a draw and found an NE567.
 
Have not been able to duplicate your fault but circuit here running  OK.
 
 
Circuit tried here:
 
Timing resistor   15k
timing capacitor  0.022uF
 
Results:   from  1 / 1.1 RC =  2755 Hz
Measured:  Oscillator frequency  2960 Hz
 
Which seems OK given the usual tolerance of the capacitors.
 
So, it must be a difference in your circuit.
 
I have.
 
Pin
1  0.47 to gnd
2  0.47 to gnd
3  0.47 input capacitor.  -ve end to pin 3
4  +5V supply decoupled with 10uF to gnd
5  15k to pin 6
6  0.022uF to gnd
7  Gnd
8  10k load resistor to +5V supply.
 
When the circuit is in lock pin 8 goes low.
When not in lock it is at +5V
 
When on the edge of locking pin 8 will pulse low with a very short duration  
m:s ratio
Audio input required apx 100mV P-P
Oscillator output from pin 5 or 6 measured at 1V P-P
You may want to consider reducing the size of the input coupling capacitor  
to pin 3 to reduce the sensitivity to frequencies lower than say 1500Hz. That  
would reduce false triggering. - High pass filter.
 
 
 
Hope that helps, good luck with RAFT
 
 
David  G0MRF
 
 
 
 
 
In a message dated 13/12/2005 21:10:53 GMT Standard Time, bruninga@usna.edu  
writes:

RAFT  satellite will use a NE567 tone decoder chip
to detect the presence of a  PSK-31 Control user.

I need help from someone that has used  these
before.  They have always worked for me before,
but I'm  stumped now and on deadline.

The book says the freq of operation is  defined to be
1.1 divided by the product of R x C.
I'm using 12 k and  .047 uF which should give
about  2000 Hz.  Problem is the PLL  runs at 
about 1200 Hz and the only input that
triggers it is 600 Hz not  2000 Hz and there are 
no other false indications.  

It simply  works solidly at 600 Hz just as advertized, 
but there are two facts that  are inconsistent with
the book:
----
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