[time-nuts] SRS FS 730
magnus at rubidium.dyndns.org
Fri Mar 22 16:20:31 EDT 2013
I got the oppertunity to measure a cesium with my TimePod, I hooked up
on the FS 730/1 and noticed a bump in the phase-noise. I by-passed it
and the bump was not there. Turns out that it had a 20 dB increased
phase-noise at 700 Hz. So, we tried the other FS 730/1 they had, and it
showed the same 20 dB increase, but at 2 kHz. It was not changing with
load. There was a fair amount of 50 Hz and 150 Hz in the spectrum too.
It was a fairly wideband rise of noise, rather than the spikes.
I did look in the schematic, but did not have the time to measure inside
Have people seen this before? A fair idea of what aspect in the design
which is to blame? Let's learn from this, right?
My ideas so far:
The input has a low-Q LC filter, could it be the noise shaped as it goes
into the input limiter, considering that the LC filter might be a little
detuned from 10 MHz.
Another theory would be a resonance in the power, but I have not found
an obvious place in power design that would be a give-away.
So, thoughts? Bob? Bruce?
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