Category: Electronics

Distribution Amp - S/N 16

Update2: Here's the 14-hour data together with a 14-hour noise-floor run. The ADEV and TDEV results are more or less instrument-limited. Only for phase-noise above 100Hz offset is the instrument floor significantly below the result for the distribution amplifier.

  • ADEV
  • phase
  • PN
  • TDEV

Update: Here's a 14 hour run of the residual phase noise, ADEV, and TDEV, as measured through the frequency distribution amplifier. Instrument is a Microsemi 3120A phase-meter.

  • ADEV
  • PN
  • TDEV

Aivon has now produced around 16 of these distribution amplifiers.

There's a new op-amp which might be interesting to try for the FDA board: THS3491. It has a grounded pad under the op-amp, so we need a new EP-variant of the PCB.

KiCad symbols and footprints

Update: Molex R/A 'long-neck' SMA-connector:

Silkscreen only on board, F.fab drawing shows off-board threaded part.

I sumbitted a few pull-requests to the KiCad libraries with some parts used on recent boards. Let's see if/when they make it into the main/released libraries...

On the to-do list is to submit an SFP-connector and Cage footprint... (unless someone has already done that?).

  • Abracon ABLNO SMD footprint
  • BNX025 EMI-filter
  • Murata BNX025 EMI-filter
  • LT1963 positive adjustable LDO
  • LT3013 negative adjustable LDO
  • Morion OCXO (sine-wave)
  • Morion OCXO
  • Morion OCXO
  • OCXO OH300 (symbol has a square-wave, but part outputs sine-wave...)
  • Connor-Winfield SMD OCXO "OH300"
  • Abracon ABLNO VCXO (100MHz)

10MHz-to-PPS board, rev2

A second try at the PPS board, this time with the correct footprint for the transistors on the sine-to-square input stage.

Still some bugs left as I had to add a diode on the MCLR pin for the PIC-programmer to work correctly.

1PPS output is phase-coherent with the 10 MHz input.
10 ms long 1PPS output, ca 2.7V into 50R load.
PPS-board, rev2. sine-to-square at the top. Sync-input and dip-switch in the middle. PPS-outputs at the bottom.
PPS into 1 Megaohm - with ringing and 3.3V amplutide..

PPS-board prototype

An evolution of my PICDIV-board from 2016. Takes 10MHz input and produces 1PPS (one pulse per second). This one has a TADD-2-mini inspired sine-to-square converter on the input (far left), a PIC12F675 with Tom van Baak's PICDIV-code (right), an ICSP-header for programming, and output-buffers inspired by the pulse distribution amplifier. A 3-position DIP-switch (middle left) allows config-changes, and a blinking LED indicates 1PPS (middle right).

Fixed a few bugs in the first PCB-revision and will order boards for version two soon. Eventually to be published on github/ohwr - stay tuned..

PPS-board 2018 August prototype. Note bypassed sine-to-square circuit on the left.

Mux-in-a-box

Update: Insertion-loss measurement with a spectrum analyzer:

RF-multiplexer v2 board in enclosure, controlled by Arduino Due with Ethernet Shield. SATA-cable for 4 SPI-lines (SI, SO, SCLK, CS).

When issuing commands to change state as fast as possible this combination seems to do a state-change in about 45 milliseconds - this is not verified on the RF-side (didn't measure that there is actual RF contact made/broken in those 45 ms).

RF Multiplexer - version 2

Version two of the RF Multiplexer adds more relays to the 8 pcs HF3 I was using in the first attempt. The added relays keep the RF-path from the selected input to the COM-output as clean as possible with no unterminated branches or stubs. The cost is anothe 7 relays with associated darlington-drivers and control-logic.

Next test is to see if there is any measurable change to the rise-time of a fast pulse-edge, e.g. from a distribution amplifier.

500 MHz SFP-board (v4)

This is the fourth version of an interface board to Small Form Factor Pluggable optical transcievers (SFPs) with a bandwidth of >500 MHz. These are useful for various time/frequency experiments, with a measured frequency stability of <1e-13 @ 1s (in 0.5 or 5 Hz bandwidth) - perhaps slightly depending on what SFP is used. The SFP allows sending the signal along a single-mode fiber for 1-100 km easily.

ADT2-1T converts to and from differential signals while LMH6702 op-amps provide 3 dB gain. There are parallel outputs on the RX pins. The current-draw on +3V3 by the SFP is quite high - usually requiring heat-sinking on the voltage-regulator

KiCad files available on request.