[time-nuts] Setting Osc Frequency

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Mar 3 22:09:55 EST 2007


VK3YV wrote:
> Hi, Tom and Bruce, many thanks for the help so far. Now I realise that I 
> will have to divide my 10MHZ reference down to match the 5MHZ from the 
> sulzers and also down to 1MHZ to use as an external ref. for the 5245L's.
> How do I change the TTL from the dividers back to a Sine wave as both 
> activities will need Sine wave inputs.
> I have no idea as to how to go about this, going the other way Sine to TTL 
> no problem but have never had to think about it. I am not an engineer just a 
> ham and the grey matter doesn't work all that well these days. Any 
> suggestions.
> One more question to bruce what is 74LCX ? I have not come across that 
> before.
> Regards Don....VK3YV. 
>
>
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>   
Don


 From TTL/CMOS is very easy just low pass filter the square wave output 
of the divider see:

http://www.wenzel.com/documents/waveform.html

If you are concerned about using a non unity mark space ratio waveform,  
don't be it doesn't have to be that exact see:

http://www.wenzel.com/pdffiles/choose.pdf

74LCX is just a variety of high speed CMOS (> 100MHz clock) that 
operates from a 3.3V supply, both its outputs and inputs will tolerate 
5V logic signals.

Bruce




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