On Mon, 20 Jan 2020 15:25:00 -0500 Bob kb8tq <kb...@n1k.org> wrote: > On Jan 20, 2020, at 2:57 PM, Mark Haun <m...@hau.nz> wrote: > > Agree except you were starting from the VFOV numbers for the 100-MHz > > version. If you use their numbers for the 10-MHz version and add > > 20 dB for an ideal 10x multiplication, for comparing with the ABLNO > > spec at 100 MHz, you end up with > > > > offset VFOV405 @ 10M, ideal 10x multiply ABLNO @ 100 M > > 10 -100 -88 > > 100 -120 -118 > > 1k -140 -141 > > 10k -145 -160 > > 100k -145 -161 > > If indeed -145 is “good enough” then you have moved out of the “good > phase noise” region into fairly generic sort of specs. A “couple of > dollar” oscillator will give you -145 sort of noise floors.
True enough, but remember that my motivation for using the OCXO in the first place was to combine the required phase-noise spec with OCXO-class frequency stability (this is for narrowband coherent modulation schemes on the shortwave bands where short-term stability of ~ 10^-10 is nice to have). The alternative is what Attila said, VCXO phase locked to an OCXO. The advantage of doing it this way is that I [potentially] reduce complexity, board space, and power. Hypothetically, sure, any old 80-MHz OCXO with "generic" phase-noise performance would suffice. But hobbyists can't just pick up the phone and order something like that; we're limited to surplus/used stock, where 80-ish MHz is unusual. And of course most surplus/used OCXOs would require high voltage (5V or above), high power (half a watt or more), or both. Sorry, I didn't plan to expound on my design rationale at such length, but you seemed curious :) Regards, Mark _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.