CaribouLite Crowd Funding Launched: A $119 30-6000 MHz 13-bit 2.5 MHz Bandwidth TX/RX SDR Hat for the Raspberry Pi

Back in June of this year we first posted about the upcoming CaribouLite product which is a software defined radio HAT for the Raspberry Pi. The project has just launched on Crowd Supply with a price tag of $119 for the CaribouLite, and $69 for a CaribouLite ISM only band version. The product is expected to ship in May 2022. CaribouLabs write:

CaribouLite is an affordable, open-source, dual-channel software-defined radio (SDR) platform—and an SDR-focused FPGA development framework—implemented as a Raspberry Pi (RPi) HAT. CaribouLite turns your Raspberry Pi single-board computer (SBC) into a self-contained, dual-channel radio Tx/Rx that spans a wide tunable frequency spectrum up to 6 GHz.

The CaribouLite RPi HAT

The CaribouLite is entirely open source and designed for makers, hackers, educators, and researchers. It comes in two versions, the full and ISM band only versions. For most people the full version will be most desirable as it covers the full 30 MHz - 6 GHz range. However, certain projects may want to make use of the ISM band only version as they note that it may easier to obtain regulation compliance.

The full version comes with two TX/RX half-duplex channels, with channel one covering 30 MHz to 6 GHz, and channel two covering sub 1 GHz only. Both channels use a 13-bit ADC, capable of a bandwidth of up to 2.5 MHz maximum. The unit is capable of up to 14 dBm of transmit power.

The libcariboulite drivers support Soapy API, meaning that many SDR programs including SDR++, GQRX, CubicSDR and GNU Radio will be able to support the CaribouLite. 

One interesting design feature is that the CaribouLite does not interface with the Raspberry Pi via USB or Ethernet which is how most SDRs interface. Instead they make use of the SMI (Secondary Memory Interface) connector, which is a high bandwidth interface available on Raspberry Pi's. This is a very fast interface allowing the IQ samples to stream back and forth, however the disadvantage is that the CaribouLite will only work on Raspberry Pi devices. Although it should be possible to use the Raspberry Pi as a host device if you wanted to use the SDR on a PC.

One problem is that we note that most Raspberry Pi resellers are out of stock and the component supply crisis appears to have slowed Raspberry Pi production. So this may be an issue for purchasers who do not already have their own Raspberry Pi. However, given that the CaribouLite ships in May 2022, there may still be time to obtain a Pi.

Given the low cost, specs and features, this appears to be quite an interesting SDR that we are excited to get our hands on. Combined with a Raspberry Pi Zero we can imagine multiple portable use cases and projects that will come from this product.

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Does cariboulite support phase coherent location radar like some of the other rtl-sdr dongles?


Interesting device…

What I hope is that Caribou have concentrated on frequency stability.

Everything else can be improved by external filters and Amplifiers of various types, you get the idea.

However, if you wander about the band as your device warms up and cools down, it’s pretty much an unusable toy.

Interested to follow the development.


> However, if you wander about the band as your device warms up and cools down, it’s pretty much an unusable toy.

Where are you getting that from, I looked at the BOM and schematic and I see the total opposite.

I looked up the BOM and checked what they are using and it is two oscillators: a 0.5 ppm 26MHz TCXO for where it is important on the analogue side of the board and then a 50 ppm 125MHz XTAL for the digital side of the board where it is not going to improve the quality of the signal after it has been captured. As long as it is good enough to meet digital timing requirements it is good enough.

Analogue side (e.g. Modem with ADC and DAC)
26 MHz TCXO Oscillators XTAL OSC TCXO 26 MHz Clipped Sinewave 0.5ppm -40C +85C 2.5x2mm, 1.6-3.6V

Digital side (e.g. FPGA):
SG-8018CG 125.0000M-TJHSA3
Standard Clock Oscillators SG-8018CG 125.0000M-TJHPA3: MHZ OSC 1.8V 3.3V +/-50PPM -40C +105C O/E 250TR
SG-8018CG 125.0000M-TJHPA3


It’s just that I noticed that both the TXCO,s face the CPU of the PI and are near the Caribous FPGA, which I know can get very hot.

If both of those units are mounted in a airtight case it may be a problem…


The TCXO will maintain +/-0.5ppm over its entire operating temperature range from -40°C to +85°C, so it should be fine and if the check the position it is basically above the hdmi connector. The crystal oscillator is 125.00 MHz +/-50ppm over its entire operating temperature range from -40°C to +105°C and to be honest when the signal is digital as long as it meets the digital timing requirements all is good. But yes it does appear to be directly over the RPI CPU. The interesting part is the iCE40 LP Series Ultra Low-Power FPGA Family (which at power up uses a peak of 30mA peak at 1.2 volts ~ 36mW) will not generate much heat itself but it is sitting directly over the RPi CPU, but as long as it’s junction temperature is inside the range –55 °C to 125 °C it is all good. So the parts of the circuit that are least effected by temperature have been placed directly over the hottest part of the RPi.

If any electronics are mounted in an airtight case without cooling there is one long term effect – shorter life time for the hardware (ref: “10°C rule”- from the “Arrhenius equation” is the usual “Every 10°C increase in temperature reduces the life of electronics by half”). The two big enemies of most electronics lasting longer than about 20 years are temperature followed by electrolytic capacitors (They have a useful and a shelf life of ~20 years).


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What Raspberry Pi will it work with?

Dave H

The photo shows it mounted on a Pi Zero, but all the Pi models (except the Pi Pico) have the same expansion connector so it should connect to any of them. Any Pi model that can run the software they said is compatible should work.


If you click on the crowdsupply link in the article, past half way down on the webpage page is a link to the Datasheet and page 14-15 of that shows the GPIO pins used which is more than 26 so that means that the oldest boards with only 26-pin headers will not work at all. But any with the 40 pin header should all work since the header was standardised.


Another exciting parameters the dynamic range. But this still a question.

Jackson Dude

Hi. What preamp do we need to get ooomph out of it? 14dBm is 0.025 W. What to do with it?


Some “HAM” labeled satellite CW downlink is also transmit 14dBm and not known any reports these. Really few.


> What to do with it?
With only -10 dBm and no external amplification people have transmitted signals using WSPR modulation 1692 km (~1051 miles) at 14.0971 MHz using a 20m dipole antenna connected to a HackRF