3120A – anderswallin.net

Microsemi/Symmetricom 3120A noise floor

This was measured by taking a H-maser 10MHz signal (output from a frequency distribution amplifier) and splitting it in two for the 3120A REF and DUT channels with a ZFSC-2-1+ passive splitter.

The first measurement is with 50 Hz bandwidth and a duration of 5 minutes. The second measurement is at 5 Hz bandwidth and ran overnight for 12 hours.

Here's the ADEV plot with some typical performance-curves added.

Data from:

BVA8607: http://www.oscilloquartz.com/files/1363164953-Br_%20OCXO%208607.pdf
iMaser:http://www.t4science.com/documents/T4S%20iMaser%20Stability.jpg
PRS-10: http://www.thinksrs.com/products/PRS10.htm
53230A: http://www.anderswallin.net/wp-content/uploads/2015/04/Keysight_53230A_noise_floor.png
50cm optical cavity: http://arxiv.org/pdf/1502.02608v2.pdf
Sr lattice clock: http://arxiv.org/pdf/1309.1137v2.pdf

SRS FS710 noise measurement

Update: changing the main electrolytic capacitors as well as the tantalum caps around the 7805/7905 voltage regulators did not help. There is still about 600 mVpp of ripple on the +/- 13.9 VDC inputs to the regulators.

600mVpp 100Hz sawtooth on +/-13.9VDC inputs to voltage regulators

I replaced the electrolytic capacitors after the diode-bridge, and also the tantalums just before and after the 7805/7905 voltage regulators.

Here's a noise measurement on an old second-hand SRS FS710 distribution amplifier. I wonder if the excessive noise at 50 Hz and harmonics is within spec or a result of old age?

Measurement setup: 10MHz signal to a Mini-Circuits ZFSC-2-1+ splitter, one branch to 3120A REF-input, the other branch to the FS710 input, and FS710 output1 to the 3120A DUT input. Noise floor was measured with the same setup but bypassing the FS710.

White Rabbit Switch noise measurement

I measured the CLK2 10 MHz RF-output of two White Rabbit switches with a Microsemi 3120A. The results are similar to previous results with ADEV(1s)=1.5e-11.

When phase-locked to an external reference clock the long-term stability is obviously much better than when free-running, but for small tau, or high offset-frequency in the phase noise plot, the free running oscillator is actually better.