[time-nuts] FTS 1050A

ed breya eb at telight.com
Tue Aug 9 21:05:12 UTC 2011


If you just want to get it to an integer value, I recommend, for 
example, that you find or make a 6.0000000 MHz VCXO using a common 6 
MHz crystal, and mix it with the 6.000300 MHz using a 74HC86 XOR, 
then the 300 Hz IF can easily be low-pass filtered out and used as 
the feedback to a PLL (like 74HC4046A) which drives the VCXO. The 
other input to the PLL can be made by dividing the VCXO output by 
20,000 (with 74HC390s), resulting in 300 Hz as a reference. The net 
result is that the ovenized oddball reference will phase lock the 
common-frequency VCXO - but only close-in since the sample frequency 
is only 300 Hz - farther out phase noise will depend on how clean you 
make the VCXO. Once you get 6.000000 MHz, you can make whatever you 
want. With a little more complexity there are lots of combinations 
that could make a nice integer value (like 10.000000 MHz), and at a 
higher sample frequency - you just have to figure out what you can 
add, subtract, multiply and divide with convenient values to get 
something usable.

Ed





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