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The RFM69 series from HopeRF look like a good alternative to the Nordic radios. They have modules available for 315 MHz, 433 MHz, 898 MHz and 915 MHz. Different countries have different restrictions on each of these bands however, so here is the situation in New Zealand 1.

315 MHz

The 315 MHz module has a range of 290-340 MHz. Transmitting anywhere in that range in NZ requires a (paid) license from RSM.

433 MHz

The 433 MHz module has a range of 424-510 MHz. Most of this range requires a license, but there are a few narrow bands that can be used freely:

  • 433.05-434.79 MHz is limited to 14 dBm EIRP
  • 458.54-458.61 MHz is limited to 27 dBm EIRP
  • 466.8-466.85 MHz is limited to 27 dBm EIRP
  • 471-471.5 MHz is limited to 20 dBm EIRP

898 MHz

The 898 MHz module has a range of 862-890 MHz. 864-868 MHz is limited to 30 dBm EIRP (or 36 dBm if frequency hopping is used), the rest requires a license.

915 MHz

The 915 MHz module has a range of 890-1020 MHz. 915-928 MHz is limited to 30 dBm EIRP (920-928 MHz is limited to 36 dBm with frequency hopping), the rest requires a license. This module makes the most sense in NZ as it has by far the most spectrum available.

Spurious emissions

Generally in NZ the limit for spurious emissions is -26 dBm peak EIRP (59 dBμV/m at 10 m) 2. Additionally, the 800-915 MHz band has a limit of -49 dBm and the 928-1000 MHz band has a limit of -33 dBm.

Compliance outside 800-1000 MHz can be determined from the FCC compliance test report available from HopeRF, if we assume that it's accurate. Below 800 MHz the highest value is about 30 dBμV/m at 3 m, which corresponds to about 20 dBμV/m at 10 m assuming the test was performed properly3. Above 1 GHz there is a single peak of 55.19 dBμV/m at 3 m at the first harmonic (around 1830 MHz) 4. That corresponds to 44.73 dBμV/m at 10 m, which is 14.27 dB below the NZ limit. However, in the FCC test the module was running at the 0dBm power setting, which suggests that at a power setting of 14.27 dBm it would reach the NZ limit at the first harmonic. Since that frequency is used for cell tower transmissions in NZ, running an RFM69HW (the high-power variant) at full power might affect cellphone reception. It could still make sense to use an RFM69HW though, since some users have found it to be slightly more efficient than the RFM69W.

Compliance within the 8800-1000 MHz band is a bit tricky though; there don't appear to be any test results available for the RFM69 modules that show the spectrum around the carrier frequency. The datasheet says the adjacent channel power is -37 dBm at 25 kHz offset but doesn't give any more detail than that, so it would be best to stay within 917-926 MHz or so to be safe.

  1. As specified in the Radiocommunications Regulations (General User Radio Licence for Short Range Devices) Notice 2016 No. 2. ↩

  2. See Table 2 of the Radiocommunications Regulations (Radio Standards) Notice 2016. ↩

  3. See here. ↩

  4. For some reason the peak is at a different frequency depending on the polarisation; that doesn't really matter in this context though. ↩

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