Month: August 2024

Mains (230VAC) DC power supplies for ham radio equipment – AU

One sees a lot of discussion on social media of 12VDC power supplies for ham radio equipment. Some of the recommendations are unsafe.  Bear in mind that the user could well be a young person with little knowledge and experience and unsafe equipment may put not just themselves at risk of electrocution, but other members of the family / household, people who might try to rescue them.

Firstly, before someone rushes to correct me on the matter of 230V: Continue reading Mains (230VAC) DC power supplies for ham radio equipment – AU

Last update: 9th August, 2024, 7:10 AM

A short comparison of the latest BLHeli_S with SimonK / tgy (~2017)

This article repeats some earlier tests on two competitive ESC firmwares for sensorless brushless DC motors.

The motor chosen for the tests, a 4822-690KV, is of a type that is very popular; a flat radial flux outrunner with high pole count. These are marketed as more suitable to multi-rotors that the barrel shaped motors developed for planes, but the claims are questionable, these motors are often at higher risk of sync loss due than the barrel shaped motors and used feature regularly in forum postings of de-sync problems. Continue reading A short comparison of the latest BLHeli_S with SimonK / tgy (~2017)

Last update: 10th August, 2024, 9:10 PM

Use of port extension or e-delay to measure a dummy load

I have an MFJ-264N which does not perform very well.

A measurement of the impedance at the inboard side of the N connector jack would be informative.

So, a NanoVNA-H4  (SOL calibrated at the Port 1 connector) with short SMA(M) to SMA(M) and SMA(F) to N(M) adapter are available, but how to set the reference plane to the inboard end of the N(F) connector? Continue reading Use of port extension or e-delay to measure a dummy load

Last update: 2nd August, 2024, 1:14 PM

Some useful equivalences of very short very mismatched transmission lines

This article explains some very useful equivalences of very short very mismatched transmission lines. They can be very useful in:

  • understanding / explaining /anticipating some measurement errors; and
  • applying port extension corrections to VNA measurements where the fixture can be reasonably be approximated as a uniform transmission line.

Port extension commonly applies a measurement correction assuming a section of lossless 50Ω transmission line specified by the resulting propagation time, e-delay, but as explained below, can be used to correct other approximately lossless uniform transmission line sections of other characteristic impedance. Continue reading Some useful equivalences of very short very mismatched transmission lines

Last update: 9th August, 2024, 11:57 PM