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Itärastit Ämmässuo

A fairly late orienteering season opening this year.

#1, #2, #3 fairly ok. Then slow on the side of the hill towards #4 - right of the line on the flatter top of the hill would be better. Down from #4 in an S-curve to the road. From the road no good plan through the green to #5.

#6-#7-#8 ok before checking out a false flag just before #9.

The ugliest squiggle is at #13 where I fail to see the 90-degree turn over the swamp that leads to the control-circle and instead cross the swamp almost straight north (90-ish degrees off course) and stop just in the to see a glimpse of #13 through the open flat woods. Looking at the compass before crossing the swamp would have been good.

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.

AllanTools 2018.03 now LGPL

By popular demand, AllanTools 2018.03 is now released under LGPL license.

Get it at: PyPi or github.

Work with integrating noise-identification with downstream confidence-interval estimation and bias correction continues as time permits.

PPP comparison with PPP-tools

Here's an example of using PPP-tools to compare PPP solutions from NRCan gpsppp, ESA gLAB, and RTKLIB.

It seems that all programs fix the lat/lon output. However both gLAB and RTKLIB leave the height as a variable parameter. Interestingly it seems there is some peak at the end of the PTBG data and gLAB compensates by raising the height while RTKLIB compensates by raising the clock value.

RF Multiplexer - first try

And now an entry in the "Plan to throw one away" section.

RF Multiplexer, 8 inputs, 1 output, BNC-connectors, TE HF3 relays specified to 3 GHz, an ULN2803A to pull the relay-coil, and an SPI I/O expander to drive the ULN - should be easy - right?

Well no, PCB trace-geometry does strange things beyond VHF. I clearly don't grok UHF very well.

Onward towards version 2! (any thoughts and advice on simulation or trace-geometry optimizers appreciated!)

Aivon LTD makes FDA/PDA ohwr-design

My open-hardware design for a 1:8 pulse and frequency distribution amplifier is now available from Aivon LTD.

ISOPDA - 1:4 Isolated Pulse Distribution Amplifier

For isolated 1PPS distribution I made this distribution board.

The input is a TLP117 (or similar) optoisolator driving a LT1711 comparator with a 1.0 V trigger level. An output LED-blink is provided by LTC6993. Outputs are driven by IDT5PB1108 buffers.

In jitter measurements with a HPAK 53230A counter the jitter between two 1PPS pulses (from masers) seems to degrade slightly through this amplifier: from RMS 16-19 ps directly on the maser-outputs to between 21 and 26 ps RMS from the outputs of the ISOPDA. Maybe a faster optoisolator would be better?

KiCad sources available on request.

Lab@Home

A mere ~3months 🙂 after moving to a new place I setup the lab-table again.

  • Ikea table 120cm wide and 80cm deep.
  • Top shelf on 40cm legs, 40cm deep.
  • HPAK E3640A powersupplies
  • 2-ch 62MXs-B 600MHz scope
  • SDG2042X siggen
  • HPAK 34401A and Fluke 177 DMMs
  • Olympus SZ51 microscope with LED ringlight
  • Hakko FA-400 and FX-888D for soldering
  • SR620 counter

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