Compared to the 2.4 GHz WiFi/Bluetooth radios on the Pi already, these modules

run at 433 or 900 MHz (sub-GHz). You can't send data as fast but you can send

data a lot farther. These packet radios are simpler than WiFi or BLE, you don't

have to associate, pair, scan, or worry about connections. All you do is send

data whenever you like, and any other modules tuned to that same frequency

(and, with the same encryption key) will receive. The receiver can then send a

reply back. The modules do packetization, error correction and can also auto-

retransmit so it's not like you have worry about everything but less power is

wasted on maintaining a link or pairing.

These modules are great for use with other microcontrollers with matching

radios (like say our RadioFruit Feathers), say if you want a sensor node network

or transmit data over a campus or town. The trade off is you need two or more

radios, with matching frequencies.

These radio modules come in four variants (two modulation types and two

frequencies) The RFM69's are easiest to work with, and are well known and

understood. The LoRa radios are exciting and more powerful but also more

expensive.

This is the 900 MHz RFM69 radio version, which can be used for either 868MHz

or 915MHz transmission/reception - the exact radio frequency is determined

when you load the software since it can be tuned around dynamically. These are

+20dBm FSK packet radios that have a lot of nice extras in them such as

encryption and auto-retransmit. They can go at least 500 meters line of sight

using simple wire antennas, probably up to 5Km with directional antennas and

settings tweakings.

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Packet radio with ready-to-go CircuitPython libraries

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SX1231 based module with SPI interface

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+13 to +20 dBm up to 100 mW Power Output Capability (power output

selectable in software)

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50mA (+13 dBm) to 150mA (+20dBm) current draw for transmissions,

~30mA during active radio listening.

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Range of approx. 500 meters, depending on obstructions, frequency,

antenna and power output

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Create multi-point networks with individual node addresses

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Encrypted packet engine with AES-128