Category: Measurement

nanoVNA-H – can firmware be updated if it has a broken USB socket?

The usual method used for firmware upgrade is DFU (Direct Flash Update) using the USB interface and one of many PC clients to load the firmware.

Before attempting a firmware upgrade, be certain of the hardware you have, and the appropriate / compatible firmware file and format. Look for a label on the back, or on the silkscreen of the PCB (though sometimes hidden under the battery… doh!)… know what hardware you have to ensure you load compatible firmware.

Before discussing how to upgrade firmware if the USB interface is not functional, be sure that this problem is not driver related, that there is a real hardware problem. Continue reading nanoVNA-H – can firmware be updated if it has a broken USB socket?

Last update: 5th February, 2023, 8:23 PM

Motorola R2009D OCXO startup

This article documents the startup characteristic of the OCXO in a Motorola R2009D comms analyser.

Frequency error from cold start was logged using the FA-3-6G counter to make record of the time for reasonable stabilisation from cold. The R2009D had been calibrated to within 100mHz some days before this test.

This test was performed with power applied to the box, but the front panel switch in standby position.

Above is a plot of the startup.

At powerup, the oscillator is 514Hz high (error 5.14e-5), at 3min error is 2.8e-5, at 5min, error is 6.4e-6, at 20min error is -1.2e-7, improvement beyond this is very slow.

The front panel “Oven ready” LED is not a good indicator that the oscillator is very close to frequency, it comes on when OCXO heater current reduces, but the oscillator has not yet stabilised.

Calibration was carried out with the whole analyser powered and operating for 24h, the oscillator will not reach calibration frequency unless the whole box is operating. Experience is that setting the reference oscillator closer than 100mHz is wasted effort.

Last update: 22nd January, 2023, 4:14 PM

BG7TBL FA-3-6G frequency meter – initial impressions

A BG7TBL FA-3-6G  is a 6GHz frequency counter of the reciprocal counter type, well for Ch1, <=300MHz, at least.) This one was purchased on eBay for just under $300 delivered.

Above is the seller’s pic of the FA-3-6G frequency counter.

It was supplied with a non-compliant Chinese plug pack, it lacks rubber feet, and the nuts on all the BNC connectors were loose, not even hand tight. Continue reading BG7TBL FA-3-6G frequency meter – initial impressions

Last update: 29th January, 2023, 9:05 PM

tinyPFA – new Nanovna-H4 arrived

TinyPFA is firmware from Erik Kaashoek for NanoVNA-H4 hardware for accurate measurement of oscillator and clock source stability.

I was so impressed with the possibilities of the project, I purchased a new Nanovna-H4 v4.3 a couple of weeks ago to dedicate to this application.

Anticipation got the better of me, and I put tinyPFA onto my existing Nanovna-H4 v4.3 to evaluate it, and was not disappointed.

Anyway, the recently ordered device arrived.

Above, the new tinyPFA at work. Continue reading tinyPFA – new Nanovna-H4 arrived

Last update: 5th January, 2023, 8:06 AM

tinyPFA – HP8656B vs Trimble Thunderbolt GPSDO

TinyPFA is firmware from Erik Kaashoek for NanoVNA-H4 hardware for accurate measurement of oscillator and clock source stability.

This article documents calibration and stability comparison of a HP8656B signal generator’s high stability reference oscillator.

Calibration

Above is a screenshot of the tinyPFA with only Trimble Thunderbolt GSPDO input, and after freq A is nulled (colours have been inverted for printing). Continue reading tinyPFA – HP8656B vs Trimble Thunderbolt GPSDO

Last update: 1st January, 2023, 8:37 AM

tinyPFA – a set of Allan Deviation plots

TinyPFA is firmware from Erik Kaashoek for NanoVNA-H4 hardware for accurate measurement of oscillator and clock source stability.

This article documents an experiment to measure the Allan Deviation of several sources:

  • Trimble Thunderbolt GPSDO;
  • Motorola R2009D service monitor; and
  • Rhode & Schwarz SML01 signal generator.

So, to make a two way comparison or three sources, there are C(3,2)=3 difference combinations, and a fourth test to document the instrument noise floor (connect the same source to both inputs).

TinyPFA and Timelab were used to make the measurements.

The GPSDO reference used was a Trimble Thunderbolt GPSDO which is locked. Continue reading tinyPFA – a set of Allan Deviation plots

Last update: 28th December, 2022, 6:42 PM

tinyPFA – first experience

TinyPFA is firmware from Erik Kaashoek for NanoVNA-H4 hardware for accurate measurement of oscillator and clock source stability.

This article documents a first experience with it performing a quite simple operation, calibrating the internal 10MHz reference oscillator of two devices:

  • Motorola R2009D service monitor; and
  • Rhode & Schwarz SML01 signal generator.

The calibration reference used was a Trimble Thunderbolt GPSDO which is locked. Continue reading tinyPFA – first experience

Last update: 28th December, 2022, 6:33 PM

An improved simple Simsmith model for exploration of a common EFHW transformer designs (v1.03)

The article A simple Simsmith model for exploration of a common EFHW transformer design – 2t:14t proposed a simple model.

The previous proposal

Above is the equivalent circuit used to model the transformer. The transformer is replaced with an ideal 1:n transformer, and all secondary side values are referred to the primary side.

The model works quite well for low leakage inductance / low ratio transformers but falls down for the higher leakage inductance / higher ratio transformers.

An improved model

The improved model is similar, but Cse in the model above is distributed to the outer sides of the lumped constant model.

Above is the equivalent circuit used to model the transformer. The transformer is replaced with an ideal 1:n transformer, and all secondary side values are referred to the primary side. Continue reading An improved simple Simsmith model for exploration of a common EFHW transformer designs (v1.03)

Last update: 13th November, 2022, 3:18 PM