KA7OEI's blog

Random musings - usually on a technical (nerdy) subject - perhaps related to amateur radio and things found at ka7oei.com and modulatedlight.org. No AI is used to generate this content.

Friday, March 14, 2025

Repairing a NanoVNA "V2" with nonsensical readings ("Blown up" input)

Figure 1: The SAA-2N, a variant of the Version 2. As noted in the text I chose this version as it had N connectors and was suited for my s...

Sunday, February 16, 2025

Ali Express "SDR TX/RX Switch" - A design NOT well thought out...

Figure 1: Front panel of the SDR TX/RX antenna switch showing the the 3.5mm audio connectors and the red/green RX/TX LED - which have been...

Sunday, January 26, 2025

A short-term capacitor-based "UPS" for mini (NUC-type) PCs

The problem Figure 1: A "Beelink" small form-factor PC. This unit sports a Ryzen processor and runs from an external 19 volt sup...

Saturday, December 28, 2024

Charging LiFePO4 batteries from a vehicular electrical system - the problems and a solution.

Figure 1: The Renogy RNG-DCC1212-20 - an isolated and current-limited battery charger, intended for use with vehicle electrical systems. Cli...

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