Since the nanoVNA got real traction a year or so back, lots of online experts have sprouted new found secrets of VNA use… and the classic is “phase is paramount”. A recent quote:
Take a look at the antenna with a VNA and sweep with the Phase function.
Let’s do that! Continue reading Phase nonsense
The RK2672AM is a Chinese high voltage test set. This article describes a process for calibration of the device.
This process should not be attempted unless you have the requisite competencies, experience, tools and test equipment. There are dangerous voltages involved, so assess the hazards, plan your work, don’t attempt it if fatigued or alcohol enhanced.
Above is the front panel of the RK2672AM. Continue reading RK2672AM – calibration
The subject vehicle is a Land Rover Defender of mixed heritage. The owner describes the engine coolant temperature (ECT) gauge as useless.
The ECT display system is a dashboard gauge and negative temperature coefficient (NTC) thermistor mounted near the engine thermostat. It measures the engine coolant temperature (hence its name) at the hottest point in the coolant circuit… so it gives the best warning that coolant might be approaching boiling point… and which point cooling capacity catastrophically falls and there is a significant risk of permanent engine damage.
It would seem that Land Rover used many different dashboard gauges, but the underlying electrical characteristics were of just two different types. Likewise there appears to be several different sensors.
The following table of coefficients for four common sensors was derived from published measurements by TSD of a single sensor of each type.
| Part | R25 | B25/100 |
| AMR3321 | 2246 | 3897 |
| ERR2081 | 2218 | 3879 |
| ETC8946 | 2450 | 3671 |
| AMR1425 | 536 | 4356 |
These are measurements of a single sample, so average values might be a little different. Additionally, the R25 / B25/100 model is only an approximation. Continue reading Diagnosis of engine coolant temperature gauge issue with a certain vehicle
This article describes a simple and inexpensive inline power meter for use as a test instrument.
The box cutouts were done on a CNC router, but they could be done with hand tools.
Above, calcs of feeds and speeds for the CNC router. The box is actually ABS, but cutting speed for Polycarbonate is the same.
Above is the tool path for one side of the box. The cutouts suit the 7P-2 strain reliefs. The gcode is generated from a custom Python file using a custom library of common shapes that I use. Continue reading A handy 230VAC 10A inline power meter based on an inexpensive module from eBay
The Baofeng UV-5R is a U/V portable FM transceiver. The battery supplied is labelled BL-5 and rated in this case at 1800mAh.
Above is the supplied USB adapter to supply power to the CH-5 charger cradle. The adapter is rated at 9V and indeed, it delivers 9.01V no load. Continue reading Baofeng UV-5R battery and charging experience
In recent articles, I flagged that on some of John’s VNWA plots he showed flawed impedance calculations using VNWA’s t2s inbuilt function.
The function t2s is documented in the VNWA help.
t2s is a VNWA built in function intended to solve the so-called s21 series through fixture for impedance measurement of two terminal Zx connected between Port 1 and Port 2.
None of John’s test fixtures were equivalent to the circuit above required for valid t2s transformation. Continue reading Comment on KN5L on balun CMRR – series through impedance fixture
