Hi I think you will find that some fairly generic oscillators will hit the “more or less 1x10^-10” sort of spec needed for HF com work. A good OCXO will get you into the 1x10^-12 range. The limit generally is the “floor” imposed by propagation variance at HF.
Bob > On Jan 20, 2020, at 3:50 PM, Mark Haun <[email protected]> wrote: > > On Mon, 20 Jan 2020 15:25:00 -0500 > Bob kb8tq <[email protected]> wrote: >> On Jan 20, 2020, at 2:57 PM, Mark Haun <[email protected]> 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 -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
