Hi
> On Nov 28, 2014, at 6:02 PM, Hal Murray <[email protected]> wrote: > > > Assume the temperature is stable Including self heating? Stable to micro-degrees / 100 seconds? Simple math: 0.1 to 1 ppm / C slope (doing quite well for this sort of part) 1 mC per second random thermal noise (not uncommon) ADEV 1x10^-9 to 1x10^-10 just due to the thermal noise and static (not dynamic, it will be higher) temperature coefficient. > and the power supply is clean Same deal - how clean? 1 ppm / V voltage stability (not un-heard of on this sort of part) 1 mV / sec random voltage noise -> 1x10^-9 ADEV > and we aren't > testing one of the PLL units and … Sometimes it can be *very* hard to tell that in advance. The PLL / DDS units are all over the place. > > What's the ADEV and/or phase noise of a typical low cost oscillator package? One second ADEV (from the above and other things) ~ 1x10^-9 at 1 second +/- an order of magnitude. Phase noise depends very much on the chip used in the device. Floor numbers range from -120 dbc/ Hz to -155 dbc / Hz. Knowing which chip is in which part is nearly impossible, unless you are buying thousands of the same part a week. > Are there slightly more expensive parts that are a lot better? Is there > something in the data sheets to look for? A part with an ADEV or phase noise spec would be a good sign. > > > What sort of toys do I need to measure ADEV and/or phase noise? I'm > interested in hobby prices rather than expensive high-end gear. ADEV - DMTD is about the easiest thing to set up in a basement. Phase noise - quadrature lock double balanced mixer + preamp running into an audio spectrum analyzer or sound card. Both setups will be a bit easier / more general useful if you are testing at 10 MHz. If you are off at some odd frequency you may have fun finding a low noise VCXO / OCXO to test against. —————————— In general it’s a *lot* easier to build up an oscillator with discreet parts and a cheap crystal than doing all the testing of pre-built parts. Having been through this sort of sorting / testing thing before: you’ll get the testing done and order some of the “good parts”. Maybe two days have gone by. The parts you get on the second order *look* identical to the first ones. They behave completely differently…. There are a lot of circuits out there in the various magazines. Total cost to build from scratch should be < $5. The one you build will blow away anything you would buy for the same cost. Phase noise and ADEV simply are not “target specs” on a simple / low cost XO. Bob > > -- > These are my opinions. I hate spam. > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
