Description
This is a dual-amplifier development module designed for increasing receive sensitivity of LoRa nodes and compensating for long antenna feeder runs, and has the following features:
- +20dB Ultra Low-Noise Amplifier in Receive Path
- +33dBm Maximum transmit power (+3dBm input power) @868MHz.
- Onboard DC-DC converter designed to run direct from a Lithium Battery, with passthrough mode for direct 5V running.
Power specifications are as follows:
- DC supply: 1.8-5V (Powers LNA and Power Amplifier Stage)
- RX/TX Switch: 3.3V – This input is not 5V tolerant!
Device Firmware
A firmware modification is required to permit this module to operate – there needs to be a signal generated by the LoRa node to tell the amplifier to switch from RX mode to TX mode.
Firmware downloads will be available below for the most common LoRa hardware. The Power setting level is limited in these firmware builds to +4dBm to protect the amplifier from damage. Please Contact Us for any other hardware variants.
Alternatively, you can compile the firmware yourself for flashing to the hardware, and assign any pin you like for switching the amplifier, and to permit higher power levels.
Note: For the RAK boards, I have had to repurpose GPIO2 – this means that this amplifier isn’t compatible with other modules that attach to the RAK, they cannot be used at the same time! This is a temporary solution while a dedicated RAK interface board is designed!
RF Connections
The amplifier can be supplied with either SMA or IPEX connectors (or combinations thereof) for the RF input and outputs.
Boards with IPEX inputs will be supplied with an IPEX-IPEX pigtail for use with radios that have an IPEX antenna connection, such as Heltec V3, WaveShare Pico, etc.
Notes for Operation
Microwave power amplifiers are sensitive devices. They are easily damaged by the following phenomena:
- Electrostatic Discharge – Ensure that suitable precautions are taken during handling and connection to prevent an ESD event damaging the amplifier.
- Input overload – exceeding the recommended input power specification could result in damage to the amplifier.
When changing channel settings with the QR Code in Meshtastic for example, the LoRa power setting is changed!
Initial Setup
- Flash the Meshtastic node with the custom firmware required to operate this amplifier module and set up the node as any other node would be set up.
- Before connecting the amplifier, set the LoRa TX Power to <5, and power off the node once the setting has been verified.
The recommended power setting is 4, to ensure that the PA is not pushed into compression, and to avoid distortion of the transmitted signal.
Some tweaking may be required to find the ideal power level depending on the LoRa radio used, but never exceed +5dBm! Gain compression will occur, and damage could occur. At the recommended +4dBm, the output power will be between 2.6-3.2W. - Connect the amplifier to the LoRa board via the input RF connection, and power/switch connections. Some soldering of GPIO pins may be required for connection.
- Connect antenna to the output connector on the amplifier module.
Before Powerup
- Ensure the antenna used has a VSWR of <=2.0 at 868/915MHz. An antenna mismatch may cause damage to the amplifier!
- Double check connections, and ensure correct power polarity has been confirmed.
- Power ON!
After the amplifier has been installed, you should find that the reported received signal strengths from other nodes has improved significantly. This does depend on distance, antenna and feeder length.
Other nodes should report much higher received signal strengths from the node with the amplifier installed, thanks to the improved transmit power level.
- Please ensure that the Effective Radiated Power remains within legal limits for your locality at all times! We take no responsibility for transmitting above legal ERP. These amplifiers are intended for use by advanced/licenced radio users and radio developers.
- All modules are tested for correct S-Parameters before dispatch. No replacements will be issued for amplifiers damaged as a result of improper usage or connection.
Note to purchaser:
This device is an advanced microwave amplifier module intended for development and investigation purposes only by radio engineers, and is not intended for use by inexperienced or untrained users. The user is responsible for connection, proper usage conditions, and ensuring that the module is run within recommended operating parameters.
This device is intended for use in burst mode operation as it is designed for data transmission purposes. Continuous transmission will cause overheating, and potential damage to the amplifier.
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