[time-nuts] xtal oscillator phase noise

John Ackermann N8UR jra at febo.com
Tue Jan 1 13:23:54 EST 2008

Mike Feher said the following on 01/01/2008 09:47 AM:
> Yes, that is what I figured regarding the 12V. For me, it has more or less
> been a rule of thumb, but, I think at 10 MHz the best you could do, due to Q
> and transistor noise and gain, was about - 155 dBc/Hz at about 100 Hz from
> the carrier. I do not recall from your earlier post what you are actually
> measuring. I would think anything close to - 150 dBc/Hz would be very good.
> That is of course if you can even measure it at its fundamental frequency. -
> Mike

For what it's worth, the Wenzel 5 and 10 MHz ULN oscillators are
generally considered to be about the lowest noise oscillators
commercially available.  They really shine in their noise floor.
There's actually (at least) one 5MHz oscillator with a better 1Hz offset
spec -- the Oscilloquartz 8607-08 BVA at -130 dBc/Hz, though its noise
floor at about -160 dBc/Hz is nothing like the Wenzel's.

Here's some data on the Wenzel units from their web site:

	5 MHz		10 MHz
1 Hz	-120		-105
10 Hz	-150		-135
100 Hz	-170		-160
1 kHz	-176		-173
10 kHz	-176		-175

(I recall having seen some 10 MHz specs on the web site that were a
couple of dB better than shown here, but these are what I could find
today for the "BlueTop ULN" which is their top of the line unit.)


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