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Finally an ultra-low power Arduino board with build-in RF and able to run your AVR projects for years on a single AA battery!
This is now a product, more details on the link below:
Finally an ultra-low power Arduino board with build-in RF and able to run your AVR projects for years on a single AA battery! This is now a product, more details on the link below:
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187 backers pledged AU$ 15,245 to help bring this project to life.

Choosing the Right Frequency

Posted by Talk² (Creator)

Soon all backers will be receiving a survey to send shipping address and other details. One important question is related to the RF frequency of your Talk² Whisper Node. But before giving an overview about the frequency options find below some updates on the current progress.

PCB Final Design and Upgrade Kits

The final board will have some extra features compared to our last prototype. As mentioned before, we're adding 2 user buttons, a Picoblade 1.25mm connector for the battery, mounting holes and some extra pads on the bottom for upgrades.

The official upgrade Kits available at the moment are:

  • RTC based on Maxim DS3231 (with built-in crystal and temp. sensor)
  • An additional 1117 LDO in case you wish to power the node with, let's say 12V
  • A CR2032 coin-cell SMD battery holder
  • 3dB external antenna with 1.5m cable length
  • 2xAA or 2xAAA Battery holder with Picoblade connetor

Except for the Antenna and Battery holders, the upgrade kits consist in a few SMD components already selected and ready to be soldered on your Whisper Node. So it's time to start practicing some SMD soldering!

The Kits are already available in our Store (, but hold on just a bit more and we'll be sending some special offers for all backers, including free or very low shipping costs for most of the cases.

Testing Plan and Default Firmware

On the coding side, we're also very busy designing our Testing Plan. The boards will be individually programmed and tested to make sure everything works. Every node will also have an unique serial number, which will be used for quality control and board production notes.

All boards will have a self-testing application running and be ready to receive a new firmware over the air. For that reason we're writing some nice features to the Bootloader, which is the essential piece for all of that to work.

Moreover the board will be able to factory reset, re-programming itself with the original application and getting ready to receive an OTA firmware upgrade. This feature turns your Whisper Node into a real 100% wireless system, being able to have nodes never connected to a cable/computer in life.

Choosing the Right Frequency

Soon you'll be receiving the survey to collect some shipping details and other required information. One of the question will be related to the RF frequency you wish to receive your Whisper Node. The options available are:

  • 433Mhz, covering from 424MHz to 510MHz
  • 868MHz, from 862MHz to 890MHz
  • 915MHz, from 890MHz to 1020MHz

On all modules the RF Chip is the same, the Semtech SX1231, but the passives are slightly different to be optimized for different bands. Also the antenna shipped with your Whisper Node will match the chosen frequency.

Open Frequencies Overview
Open Frequencies Overview

Before you pick one, it's important to understand that each country/region has different legislation. The map above show the big-picture about the open frequencies around the world. We are not able to research and validate every single country, but we've collected the most common ones:


Standards LIPD:


  • All transmitters 433.05–434.79 up to 25mw
  • Telecommand or telemetry transmitters 472.0125–472.1125 up to 100 mW
  • Digital modulation transmitters 915–928 up to 1 W
    The radiated peak power spectral density in any 3 kHz must not exceed 25 mW per 3 kHz


ETSI EN 300 220-1 V2.4.1 (2012-05):
ETSI EN 300 220-2 V2.4.1 (2012-05):

There's a new version to be published soon ETSI EN 300 220-2 V3.1.0 (2016-05)


  • 433MHz up to 10mw
  • 868MHz normally up to 25mw. 500mw from 869.4MHz to 869.65MHz

Check ETSI for all frequency details.


FCC 47 part 15 subpart C 15.247:


  • 915MHz Band Digital modulation up to 1W peak

Semtech Application Notes

Find on the link below some details and analysis from the RF Chip manufacturer, Semtech, related to the FCC regulation and the use of Digital Modulation.

Final Word

Please feel free to ask questions if you're unsure about the Upgrade Kits, OTA Firmware Upgrade or the recommended RF Frequency.

Also, if you wish to comment about the recommended frequencies, always attach an official link from where you got the information from. Do not use forums, wikis or other non-official source of information as many details are constantly changing and can cause confusion to the audience.

Mike M.

Elrico, Talk², and 7 more people like this update.


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    1. Talk² Creator on

      Hello Dag, both 433MHz and 868MHz bands are OK to use. In terms of regulation the 433MHz is limited to 10mw (10dBm) of transmission power, where 868MHz the legislation allows transmission up to 25mw and even 500mw in some cases.

      I don't live in Europe but I understand that the 868MHz band can be quite busy in some populated areas, as the band is used by commercial applications like Alarms, including some Fire and Smoke detectors.

      In practical terms I haven't notice any significant difference in terms of reliability, range or penetration when testing the 433MHz and 868MHz radios. The only difference would be the antenna size, where a 433MHz would normally require a bigger antenna. Saying that the antenna supplied with Whisper Node is "externally" exactly the same for all bands, around 120mm long, changing only the size on the internal parts.

      In a summary, if you don't have special requirements for the frequency and you're not planning to use the High-power version of Whisper node, you should be OK with 433MHz. In case you plan to use the High power in the future might be better to stick with the 868MHz as the legislation allows stronger TX power.

      Regarding the last question the simple answer is NO. The RF semi-conductor manufacturer implements a proprietary modulation/protocol/technology. As most of the sub-GHz devices, unfortunately there's no standard that allows multi-vendor devices to communicate to each other, even when using the same frequency, the signals will just appears as interference or noise to the chip.

    2. Dag Henrik Bråtane

      I am still unsure which frequency to select for Norway (Europe). Is a good choice 433 MHz or would 868 MHz be better? And why is one better than the other? Another question: If I select 433 MHZ, will Whisper Node be able to communicate with other 433 MHz systems?