In a message dated 16/08/01, cellectronic@.............. writes:

> Does anybody have a circuit diagram or know where I can find one for a 600 
> Hz tone decoder, weather it be a PLL design or dedicated frequency to 
> voltage converter is not important. I assume most analogue telemetry links 
> use the method of a varying tone relative to seismic signals as is the case 
> with my setup, I am currently using a tuned coil for a freq/volt converter 
> 

Dear Steve,

       I assume that you wish to output a tone to your radio link which is a 
frequency analogue of the input voltage and then recover a voltage from the 
receiver. (There are standard amateur radio circuits for providing for 
frequency shift keying of digital signals) If you look up the applications 
information in the LM331 Voltage to Frequency Converter and the LM2917 
Frequency to Voltage Converter data sheets, you will find standard 
'precision' circuits available.
 
       If you wish to use a phase lock loop to give some immunity from RFI, I 
suggest that you consider using a CD4046 PLL for both the oscillator and 
decoder. The input voltage / frequency output of the 4046 is vaguely S shaped 
due to the characteristic of the input source follower FET and the source 
resistor. This can be eliminated using a CA3130 opamp. If you put the input 
voltage onto the + in p3 of the opa, the opa output p6 onto the Vin p9 of the 
4046 and the -in p2 of the opa onto the junction of the source resistor and 
4046 p11, this will force the input voltage / current / frequency 
characteristic to be dead linear. The improvement is considerable. 

       Have you noted the EV-17 1 Hz seis mentioned in Larry's message of 
15/08/01? 

       Regards,

       Chris Chapman
In a message dated 16/08/01, cellectronic@.............. writes:



Does a
nybody have a circuit diagram or know where I can find one for a 600 

Hz tone decoder, weather it be a PLL design or dedicated frequency to 

voltage converter is not important. I assume most analogue telemetry links 

use the method of a varying tone relative to seismic signals as is the case 

with my setup, I am currently using a tuned coil for a freq/volt converter 

and are looking into other possibilities of achieving this. 



Dear Steve,



       I assume that you wish to output a tone to your radio link which is a 

frequency analogue of the input voltage and then recover a voltage from the 

receiver. (There are standard amateur radio circuits for providing for 

frequency shift keying of digital signals) If you look up the applications 

information in the LM331 Voltage to Frequency Converter and the LM2917 

Frequency to Voltage Converter data sheets, you will find standard 

'precision' circuits available.

 

       If you wish to use a phase lock loop to give some immunity from RFI, I 

suggest that you consider using a CD4046 PLL for both the oscillator and 

decoder. The input voltage / frequency output of the 4046 is vaguely S shaped 

due to the characteristic of the input source follower FET and the source 

resistor. This can be eliminated using a CA3130 opamp. If you put the input 

voltage onto the + in p3 of the opa, the opa output p6 onto the Vin p9 of the 

4046 and the -in p2 of the opa onto the junction of the source resistor and 

4046 p11, this will force the input voltage / current / frequency 

characteristic to be dead linear. The improvement is considerable. 



       Have you noted the EV-17 1 Hz seis mentioned in Larry's message of 

15/08/01? 



       Regards,



       Chris Chapman