Radioberry SDR: Everything You Need to Know
The Radioberry is an open-source, full-duplex High Frequency (HF) Software Defined Radio (SDR) transceiver designed to operate as a Raspberry Pi HAT (Hardware Attached on Top). Originally developed by PA3GSB, it transforms a standard Raspberry Pi into a highly capable, standalone SDR by utilizing the Pi’s GPIO pins for power, firmware loading, and data transfer.
Hardware Architecture
Instead of relying on a traditional mixer and local oscillator, the Radioberry uses Direct Down Conversion (DDC) for receiving and Direct Up Conversion (DUC) for transmitting.
The board is built around two primary silicon components:
- Analog Devices AD9866: This is a 12-bit broadband modem mixed-signal front-end chip. It handles the actual digital-to-analog and analog-to-digital conversions for the RF signals.
- Intel Cyclone 10LP FPGA: This Field Programmable Gate Array (typically the 10CL016 or 10CL025 variants) sits between the AD9866 and the Raspberry Pi. It handles the heavy DSP (Digital Signal Processing) workload, filtering, and decimating the massive flow of RF data before sending it to the Pi.
Technical Specifications
| Feature | Specification |
| Frequency Range | 0 – 30 MHz (covers the entire HF spectrum) |
| Maximum Bandwidth | Up to 384 kHz |
| Receive (RX) | Up to 4 simultaneous RX channels |
| Transmit (TX) | 1 TX channel |
| TX Output Power | ~20mW (13dBm) straight from the bare board |
| Protocol | HPSDR (High Performance Software Defined Radio) Protocol-1 (Hermes Lite 2 compatible) |
Note on Transmitting: Because the bare board only outputs around 20 milliwatts, it requires external filtering (like a Low Pass Filter) and a linear amplifier to be used as a practical transmitter on the amateur bands.
Software & Ecosystem
Because the Radioberry uses the open HPSDR (High-Performance Software Defined Radio) protocol, it is compatible with a wide ecosystem of SDR software across different operating systems:
- pihpsdr: A popular choice for running the radio natively directly on the Raspberry Pi.
- Desktop SDR Clients: It works seamlessly over a network with programs like SDRConsole (V3), HDSDR, and SDR#.
- Radioberry Juice is a hardware expansion board (an interface board or USB hat) that connects a Radioberry SDR module to a computer or alternative single-board computer via USB, bypassing the need for a Raspberry Pi. Requires specific “Juice” firmware/gateware loaded onto the FPGA to handle the USB data stream.
Raspberry Pi Compatibility
The Radioberry relies on highly specific GPIO timing for SPI communication with the FPGA. Because of this tight hardware coupling, the project officially targets the Raspberry Pi 4.
Recent iterations of the Raspberry Pi (like the Pi 5) introduced significant changes to the underlying GPIO hardware architecture. As a result, standard Radioberry firmware does not work plug-and-play on the Pi 5, requiring advanced workarounds or alternative data routing methods to function on the newer boards.
Adding a Linear Amplifier and Low Pass Filter to a Radioberry SDR
To increase the transmit power of your Radioberry for amateur radio use, you need to establish a clear signal chain: Radioberry TX Out ➞ Linear Amplifier ➞ Low Pass Filter (LPF) ➞ Antenna.
Here is the step-by-step breakdown of how to integrate these components effectively.
1. Connecting the RF Signal
The Radioberry has two SMA connectors on the board: one for Receive (RX) and one for Transmit (TX).
- Connect a 50-ohm coaxial pigtail from the Radioberry’s TX SMA connector to the RF Input of your linear amplifier.
- The bare Radioberry outputs roughly 10mW to 20mW (10-13 dBm). This is typically enough to drive the input stage of many homebrew linear amplifiers, such as those utilizing IRFP150 MOSFETs, to produce a substantial output.
2. TX/RX Switching (PTT vs. RF Sensing)
When you hit transmit in your SDR software, the amplifier needs to know to switch its relays from bypass (receive) mode to amplify (transmit) mode. There are two ways to handle this:
- Hardware PTT: The Radioberry provides a PTT (Push-To-Talk) pin on its IO connector. This pin goes high (or low, depending on configuration) during transmit. You can wire this to the PTT input of an amplifier.
- RF Sensing (Carrier-Operated Relay): If you are using an amplifier design like the VU2EVQ 100W linear amplifier, a dedicated hardware PTT line from the Radioberry is not required. These designs feature a built-in carrier-operated relay with RF sensing. The moment the Radioberry sends the 20mW RF signal, the amplifier detects the carrier and automatically switches the relays into transmit mode.
3. Integrating the Low Pass Filter (LPF)
A linear amplifier will amplify the fundamental frequency of your signal, but it will also generate unwanted harmonics (multiples of your operating frequency).
- Placement: The Low Pass Filter must always be placed directly after the linear amplifier’s RF output and before the antenna.
- Function: If you are operating on the 80m band, for example, your LPF will allow the 3.5 MHz signals to pass through to the antenna while heavily attenuating the 7 MHz, 10.5 MHz, etc., harmonics generated by the MOSFETs.
- Never transmit through a linear amplifier without an appropriate LPF for your operating band, as it will cause out-of-band interference.
4. Software and Hardware Configuration Notes
Because you are routing the RF out to an amplifier, ensure your SDR software (like pihpsdr or SDRConsole) has the “Drive” or “TX Gain” settings adjusted properly. Start at a low drive level and slowly increase it while monitoring the amplifier’s output to avoid overdriving the MOSFETs.
Additionally, ensure your Radioberry drivers and GPIO configurations are specifically set up for your host board, as newer hardware like the Raspberry Pi 5 handles the necessary SPI timing differently than the Pi 4.