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Hardware and Antennas

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ha-taggle edited this page Nov 2, 2026 · 3 revisions

Hardware and antennas

You need three things: a USB radio, an antenna and a computer to plug it into. Check the single tested setup before buying anything. Other receivers, transmitters and areas remain unverified.

Tip

Shopping list

  • RTL-SDR USB receiver: RTL-SDR Blog V4 (the only receiver field-tested with ha-taggle)
  • Antenna suitable near 922 MHz: a bare receiver may not include one. The RTL-SDR Blog dipole kit can be adjusted as described below
  • USB extension cable, 1–3 m
  • A host computer: whatever runs Home Assistant, or a Pi, mini PC or NAS

The radio: RTL-SDR

An SDR (software-defined radio) is a radio where the tuning and decoding happen in software. RTL-SDR is the name for USB SDRs built around a Realtek RTL2832U chip. They were originally TV tuners, and people later found they could receive a huge range of frequencies.

USB receiver Status Notes
RTL-SDR Blog V4 Tested. The only one used in the confirmed setup. Production has ended. Buy genuine remaining stock from the official reseller list. Many marketplace listings are fakes. The containers include the RTL-SDR Blog driver it needs.
RTL-SDR Blog V3 Unverified with ha-taggle Not part of the tested shopping recommendation
Generic "RTL2832U" TV sticks Unknown Quality varies a lot

Budget about AUD 60 for a USB receiver as a rough guide. Kits and shipping vary.

Note

The RTL-SDR Blog has a V4 user guide and a quick start guide. You don't need to install their Windows software for ha-taggle, but the guides explain the hardware well.

The antenna

The supported receive path targets a carrier near 921.995 MHz, with an SDR centre of 922.2 MHz by default. The SP3C datasheet specifies 915–928 MHz for that product; other Taggle installations can use different bands or cellular radio. Your antenna should suit the supported channel.

Why about 8 cm? (the maths, gently)

A simple antenna works best when its length relates to the radio wave's wavelength, the distance a wave travels in one cycle.

  1. Radio waves travel at the speed of light, about 300,000,000 metres per second.
  2. At 922 MHz, the wave repeats 922,000,000 times per second.
  3. Wavelength = speed ÷ frequency = 300,000,000 ÷ 922,000,000 ≈ 0.325 m = 32.5 cm.
  4. A quarter-wave antenna is one quarter of that: 32.5 ÷ 4 ≈ 8.1 cm.

The quarter-wave monopole is one of the most common antenna designs in the world. Across the whole 915–928 MHz band the answer barely changes (8.1–8.2 cm), so "about 8 cm" is fine.

Using the RTL-SDR Blog dipole kit

The V4 and V3 often come with a dipole kit: two telescopic arms on a base. A dipole is two quarter-wave arms pointing in opposite directions.

  1. Fit the small telescopic arms.
  2. Set each arm to about 8 cm in total. The RTL-SDR Blog's dipole guide says to allow about 2 cm of metal inside the base. So about 6 cm visible per arm gets you close.
  3. Make both arms the same length.
  4. Start with the arms pointing straight up and down, then try other angles if reception is weak. Compare by SNR over several hours.

Tip

The exact length matters less than where you put the antenna. The dipole guide also notes that exact length "does not matter too much". Height and line of sight usually help more.

Placement

  • Get it near a window that faces the meter box, or as close to the street side of the house as you can.
  • Higher is better. A shelf beats a floor.
  • Use the USB extension cable. Keep the USB receiver away from your computer, NAS or router, which give off radio noise.
  • Avoid metal. Foil insulation, metal roofs and steel cabinets block signals.
  • After each change, wait for at least one full hour of transmissions before judging. See First scan.

The host computer

Host Notes
The machine already running Home Assistant Simplest. The add-on supports amd64 (most PCs) and aarch64 (64-bit ARM such as Pi 4/5).
Raspberry Pi 4 or 5 Fine. Use a good power supply, because the USB receiver draws power over USB.
Mini PC (Intel/AMD) Fine.
NAS with Docker Fine if Docker can access USB devices. See Installing with Docker.
Virtual machine You must pass the USB receiver through to the VM.

Note

Why might the CPU matter? ha-taggle processes 2.4 million radio samples per second, continuously. Older or very low-power boards may struggle. If you see gaps, check the host isn't overloaded.

Only one program can use the USB receiver at a time. Stop any other SDR software (like dump1090 or rtl_433) using the same USB receiver, or buy a second USB receiver.

Technical detail: transmitter support

An RTL-SDR with USB access, an antenna suitable for 915–928 MHz, and Home Assistant with its MQTT integration and a broker are required. Container builds include the RTL-SDR Blog driver, including V4 support. The default centre is 922.2 MHz, at 2.4 MS/s; reception targets one known channel near 922 MHz, rather than all Taggle deployments.

Format / radio Available information Validation
18 bytes, clear ID, three raw counter slots, hourly usage, SNR and signal level One Gladstone transmitter with a Blog V4, plus generated tests
21 bytes, clear ID, three raw counter slots, hourly usage, SNR and signal level Generated tests only; no field confirmation
24 bytes, encrypted ID, SNR, signal level and last seen only Generated tests only; usage cannot be decrypted
NB-IoT / cellular Not receivable Unsupported

Appearance and model-family names do not establish compatibility. The tested transmitter's exact model is unconfirmed. Encrypted messages provide no usage data. See Finding your meter, How it works for the signal flow, and Protocol for the radio layout.

Further reading

ha-taggle is experimental, receive-only and unofficial. It is not affiliated with Taggle Systems or any council or utility. Only receive your own meter, and never touch the utility's equipment. All IDs in this wiki are fictional. · Repository · Report an issue · Glossary

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