DIY DSOXLAN

Let's say you have a DSO-X 2000 or 3000 series oscilloscope and you're not super keen on paying about 300 euros for the brand-name DSOXLAN module to enable the Ethernet port it already essentially has on board? No worries, just build yourself this DIY DSOXLAN module! The most expensive part of this build is the 8 euro magjack Ethernet connector.

Sources: https://github.com/aewallin/DSOXLAN

In other news this blog has been updated to WordPress 4.1. Hope everything works OK.

SMD R/C kit

  • Inspiration and labels from: DIY SMD Resistor Capacitor Kit. I enhanced the labels with tolerance and wattage/voltage infromation as well as color-coding.
  • Boxes: www.shenzhen2u.com
  • Components: Digikey
  • Resistors 1x, 2x, 3.3x, 4.99x over 5 decades from 10 Ohms to 100 kOhms. All 0805 size.
  • Capacitors: 4.7x and 10x over 7 decades from 1pF to 10uF. Smallest 0603, mostly 0805, and largest 1206 size.
  • Bugs: X7R is misspelled as XR7. One printed label was lost in production. My choice of components uses 36 out of 40 boxes - still room for 4 more components.

smd_boxes_40boxes

smd_boxes_closeup

Agilent DSO-X 3034A

I got a 4-channel 4 GS/s 350 MHz Agilent DSO-X 3034A scope on ebay!

So far I've just explored the Easter eggs built into the firmware :)

White Rabbit Switch PPS-output test

We got some White Rabbit Switches and I did an initial test of the pulse-per-second (PPS) output stability. In contrast to earlier measurements that showed 200ps or so of white phase noise, the PPS output on the WRS now seems a lot more stable. For various reasons the noise-floor (red data) of our 53230A time-interval-counter is at around 50e-12 @ 1s, and the WRS PPS output is at very much the same level of stability. Another 53230A counter shows about 13 ps standard-deviation for a cable-delay measurement - so I may redo these measurements with that counter. In any case a real evaluation of the short-term stability requires a DMTD measurement at 10 MHz.

53230A counter input channel fix

Update: after the fix the counter seems OK again. 12 ps standard deviation (61k PPS-pulses, collected over 17 hours) on a cable-delay test:
54230A_cable-delay

53230A_fix

A broken CH1 input trace seems to be a common problem on the Agilent/Keysight 53230A counter. This is the second unit with the same problem we have seen.

The fix is to bypass the broken trace with a wire directly from the center of the input-BNC to the next unpopulated SMD-pad.

Clock Laser beat-note

Here's the beat-note, as seen on a spectrum analyzer, between a red laser at 445 THz (or 674 nm, if you prefer wavelengths instead of frequencies) and a femtosecond frequency comb. The frequency comb has evenly spaced (100 MHz in our case) 'teeth' at well-defined multiples of RF-frequencies that we can lock to a H-maser. This allows absolute frequency measurements of the optical frequency at 445 THz. Currently we are trying to improve the SNR of the beat-note so that a frequency-counter will give a stable output reading of the beat-note frequency. The video shows about 20 dB of SNR using 10 kHz RBW (if you are optmistic), but reliable counting requires around 25 dB SNR using a 100 kHz RBW.

This laser will be used as the 'clock-laser' in our  ion-clock where it is used to drive a narrow clock-transition of a single laser cooled Sr+ ion. Earlier I blogged about measuring the thermal expansion of the optical cavity that is used to stabilize the laser.

Rack PC Build - Part Two

Another rack-PC put together this week. Intel X99-chipset with LGA2011-3 CPU socket. Only PCI-e slots, no legacy PCI-slots.

Again I didn't get the polarity of the HDD-LED and Power-LED wires right on the first try. How come the industry cannot agree on a standard connector for the bundle that has the power-switch, reset-switch, HDD-LED, and Power-LED?

Another glitch was that this board has 8 slots for RAM, and the two RAM-sticks I got need to be installed exactly in the right slots - otherwise it won't even boot into the BIOS. Some reading of the motherboard manual was required.

After installing Ubuntu 14.04LTS (from USB-stick! No CD/DVD required) the NVIDIA-drivers (for the GTX750TI) were not automatically detected. I downloaded the latest driver from NVIDIA and installed it manually. This requires logging in to a text-only console (CTRL-ALT-F1), and then killing X for the duration of the install (sudo service lightdm stop)