Month: July 2024

Common mode choke measurement – length matters #4

Common mode choke measurement – length matters #2 discussed the effect that even quite short pigtails might have on the measurement of a high value resistor.

This article documents an experiment to measure a DUT comprising two 1206 0.1% 10kΩ resistors soldered to a 2w section of turned pin male header strip.

Above is the measurement fixture with the 5kΩ DUT, and the parts used to calibrate the fixture. The LOAD resistor measured 50.185Ω at DC, and that was entered into the NanoVNA for improved calibration accuracy. Continue reading Common mode choke measurement – length matters #4

Last update: 10th August, 2024, 7:33 AM

NanoVNA-H4 radio remote trial #5 – NanoVNA enhancement

A series of four articles explored different wireless solutions for remote operation of a NanoVNA-H4.

The NanoVNA-H4 can use a USB connection, or a serial connection, the UART, selected from the configuration menu. The UART ‘channel’ is a conventional unprotected asynchronous protocol, 8N1, and supports a range of DTE speeds.

Three different wireless remote solutions were trialed, and an inexpensive Bluetooth adapter showed the most promise. The air-link is a ‘reliable’ link in terms of error free transmission, though of course it depends on adequate signal strength. Importantly, even at 115200bps DTE speed, it did not seem to suffer buffer overruns, an important detail given the lack of effective flow control in the NanoVNA-H4 UART interface (as brought to the edge pads).

In response to the need for a more efficient data transfer for screenshots (~399kB), Dislord has released a version of NanoVNA-D that supports a RLE compressed screenshot download.

The Python script published at https://github.com/owenduffy/tinydevicecapture allows standalone screenshot capture using the new “capture rle” command which permits screenshot download in 2-5s at DTE speed 115200, less than a quarter the uncompressed image.

Above, a loopback throughput test at 20m outside gave throughput of 42958bps, so it is deemed prudent to configure the NanoVNA serial speed to 38400 bps to minimise the risk of buffer overruns. Transfer time for a not very busy screen is around 6s.

Last update: 26th July, 2024, 9:14 AM

Stand alone update of SiK radio firmware

SiK is an inexpensive data radio commonly used by UAVs.

At least two of the ‘ground station’ applications incorporate facility for firmware upgrade, but if you aren’t using them for their main purpose, it is a huge installation just to upgrade the SiK radio.

Above is an inexpensive C2 programmer with DIY pogo pin adapter, one of may options. A C2 programmer is needed to write the bootloader.

The SiK radio project publishes a python script at https://github.com/ArduPilot/SiK/blob/master/Firmware/tools/uploader.py . This article gives a revised version that works on a HM-TRP radio under Windows 11.

The firmware was v2.2 sourced from https://firmware.ardupilot.org/SiK/stable/ .

Here is the revised Python script: Continue reading Stand alone update of SiK radio firmware

Last update: 30th July, 2024, 7:14 AM

NanoVNA-H4 radio remote trial #4 – Summary

A series of three articles explored different wireless solutions for remote operation of a NanoVNA-H4.

The NanoVNA-H4 can use a USB connection, or a serial connection, the UART, selected from the configuration menu. The UART ‘channel’ is a conventional asynchronous protocol, 8N1, and supports a range of DTE speeds. Importantly, it does not incorporate:

  • any form of flow control; or
  • any form of error detection / correction.

Essentially, any form of wireless channel were the actual throughput is less than the DTE speed is likely to experience buffer overruns, errors. Continue reading NanoVNA-H4 radio remote trial #4 – Summary

Last update: 21st July, 2024, 6:53 PM

NanoVNA-H4 radio remote trial #3 – 3DR radio (SiK)

As part of investigation of radio remote options for the NanoVNA, a 3D Robotics (SiK) clone radio was evaluated. Firmware is v2.2.

Above is the radio. These are widely used for UAVs, indeed the firmware is optimised for that application. My assumption is that the thing implements a reliable radio link, potentially over distances to 1km or so (at 20dBm tx power). Continue reading NanoVNA-H4 radio remote trial #3 – 3DR radio (SiK)

Last update: 20th July, 2024, 4:49 PM

NanoVNA-H4 radio remote trial #2 – HC-12

As part of investigation of radio remote options for the NanoVNA, hc01.com’s HC-12 modules looked promising. Some parts were purchased and tested for the application.

Above is a HC-12-USB and HC-12 using a Si4438 chip. Another of these and two HC-12 using Si4463 chip were purchased, however Si4438 were supplied against all orders. Continue reading NanoVNA-H4 radio remote trial #2 – HC-12

Last update: 19th July, 2024, 5:29 PM

nanoVNA-H – Deepelec test jig #2

I have found you can never have enough of these things. It is very convenient to leave some measurement projects set up while work continues on some parallel projects.

Above is the kit as supplied (~$8 on Aliexpress). Note that it does not contain any male turned pin header… more on that later. Continue reading nanoVNA-H – Deepelec test jig #2

Last update: 18th July, 2024, 9:20 AM

Common mode choke measurement – length matters #3

Following on from Common mode choke measurement – length matters #2 which demonstrated that the following test fixture gave invalid results due to the 20mm length of resistor pigtails, the connection length in general terms

Above is a pic of my experimental setup. The resistor on Port 1 is a 10k 1% metal film resistor. The NanoVNA has been SOL calibrated at the Port 1 jack. Continue reading Common mode choke measurement – length matters #3

Last update: 16th July, 2024, 7:11 AM

NanoVNA-H4 radio remote trial #1 – HC-05 Bluetooth

This series of articles documents a trial of an Bluetooth link for remote operation of a NanoVNA-H4.

There are risks in fitting a radio transmitter in close proximity to RF measurement equipment. Those risks can be mitigated by just not doing it, but with care, it may be possible to achieve the utility of remote operation without degradation of the instrument.

The Bluetooth adapter is an external HC-05 adapter, <$5 on Aliexpress, configured for 38400bps.

The trial started with NanoVNA-D v1.2.35 firmware.

This should be straightforward as people claim to have this working.

Note than HC-05 modules are not all the same, and different performance may be obtained from different manufacturers products and different firmware versions. The one tested here was labelled hc01.com… but it is Chinese product and Chinese are copyists, it means little. Firmware reports version hc01.com v2.1.

AT+VERSION
+VERSION:hc01.comV2.1
OK

The module uses a CSR BC417 Bluetooth chip. The Windows end is unknown, but relatively new. Continue reading NanoVNA-H4 radio remote trial #1 – HC-05 Bluetooth

Last update: 29th July, 2024, 6:38 PM

Holzforma / Farmertec G395XP chainsaw – first impressions

I purchased a Holzforma G395XP chainsaw, it is a Chinese clone of the now discontinued Husqvarna 395XP It is a relatively old technology carburetted engine without stratified intake and without introducing electronic auto tune, a 30 year old design.

Some of the fasteners used to hold the top cowl down were noodled and would only work with a plain slotted screwdriver. They were replaced with hex button head screws.

In the light of experience with Holzforma / Farmertec G372XT chainsaw – early evaluation, a decision was made to preemptively vacuum and pressure test the G395XP saw.

It failed the vacuum test, not really badly, bad badly enough to warrant repair. Continue reading Holzforma / Farmertec G395XP chainsaw – first impressions

Last update: 12th July, 2024, 12:33 PM