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Welcome to my website! I’m Michał Słomkowski, callsign SP3OHM. I work full-time as a Java/Kotlin backend developer and Linux system administrator. Here, I usually write about my tinkering endeavors, electronics, hardware, software, amateur radio and mechanical hacks. I live in Poznań, Poland. If you want to contact me for any reason, you can find the details on the About page.

There are 43 articles on this website. The most recent articles have been published or updated:

2026-10-13, 23 min read, ~5000 words

Pluto+ SDR as Vector Network Analyzer with SATSAGEN

SATSAGEN software turns the Pluto+ SDR into a vector network analyzer measuring S11 and S21, working well above the range of the popular NanoVNA. With a surplus directional coupler and a few cheap attenuators, I used it to tune a 2.4 GHz helix antenna for the QO-100 satellite and to check other microwave components.

2026-09-01, 2 min read, ~400 words

Setting IP of APC UPS network management card

Changing the IP of an APC AP9617 network management card requires a serial console wired through the Smart-UPS itself, with APC's non-standard DE-9 cable at 2400 8N1.

2009-08-10, updated on 2026-06-26, 24 min read, ~5000 words

The HF transceiver I couldn't finish

As a teenager, I attempted to build a 0–30 MHz transceiver from scratch, going through three design iterations. None were completed; design errors and the lack of more advanced RF measurement equipment overwhelmed me. Still, I include the description here as a monument to that fascination.

2026-05-21, 3 min read, ~700 words

MikroTik: T-Mobile Polska over Vectra DOCSIS

How to replace an ISP-issued router with a MikroTik on T-Mobile Polska delivered over a Vectra DOCSIS cable network. Covers obtaining PPPoE credentials, configuring VLAN 35 required by T-Mobile, and RouterOS setup including MTU handling for baby giant frames.

2026-02-17, 10 min read, ~2300 words

Meshtastic on Orange Pi Zero 3 with E22-900M30S

Testing a Meshtastic node with an Orange Pi Zero 3 and an E22-900M30S (SX1262) LoRa module. I describe Armbian, SPI, GPIO configuration, and building an 868 MHz ground-plane antenna.

2026-01-30, 7 min read, ~1500 words

FFmpeg on Debian with NVIDIA NVENC/NVDEC/CUVID

A quick guide for FFmpeg with NVIDIA GPU support on Debian 13, including compilation and examples of hardware-accelerated video transcoding.