Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
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page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Crystal Reference Oscillator Design.
Posted: Sun Oct 21, 2007 3:25 am
Tue Feb 27, 2007 6:16 am
For the sake
of learning and my own interest, I have been designing a UHF data radio.
Is this correct ?
If my carrier freq is 450.325MHz accurate
Lets say Im using a 20MHz Crystal reference oscillator
for my PLL.
Then a rough calculation tells me that my crystal must
be accurate to within -> 20*PPM*(450.325*10^6)/(20*10^6) < 200
Where PPM is parts per million.
calculations are correct, can anyone recommend where I can find a crystal
reference ocillator with a TTL or CMOS output, accurate to 0.44PPM?
I believe an oscillator from 5MHz to 25MHz would be suitable.
FYI my channel width is 25kHz, Im using National's LMx2346. Thankyou
Regards Darcy Randall, Perth, Western Australia
Regards, Darcy Randall, Perth, Western Australia
Post subject: Posted: Sun Oct 21, 2007 5:14 am
Joined: Mon Jun 27, 2005 2:02 pm
Your calculation is correct.
For such a tough spec as you have a simple Crystal is not good enough.
You should use a TCXO. I found an example for one with 0.28PPM and
a CMOS output:
http://www.valpeyfisher.com/openlink.as ... FTX160.pdf
You can also ask for samples and define the frequeny that you
need. Please contact the manufacturer for further help.
Post subject: Posted: Sun Oct 21, 2007
Joined: Tue Feb 27, 2007 6:16 am
Darcy Randall, Perth, Western Australia