The World’s Smallest Dual-Band ADS-B Receiver Module – Pants for Birds
!Image 1: ADSBee m1421 module with dime for scale - front view.
Pants for Birds is excited to introduce a new product in the ADSBee family of open-source ADS-B receivers: ADSBee 1421!
Background
In the past year, developers and enthusiasts have brought ADSBee 1090U’s open source aircraft tracking technology to a wide range of platforms, from airport ground stations to drones to weather balloons.
While working closely with some of our customers, we discovered that many applications have a need for an ultra low-power, low-cost ADS-B receiver tuned specifically for aircraft detect and avoid applications, without the need for the full feature set of ADSBee 1090U.
Simultaneously, Semtech released their fourth-generation LoRA IP on a chip called the LR2021, which includes a new high bit rate OOK reception RF frontend and demodulator. This new chip neatly containerizes an RF architecture that was previously implemented in custom discrete components (like in ADSBee 1090U and most other receivers) drastically shrinking both form factor and power dissipation required for receiving Mode S packets. Combined with a low power RF MCU, the LR2021 provides the perfect basis for a super small, low power, low cost dual-band ADS-B receiver. We already had the perfect candidate part for the RF MCU in TI’s CC1314, the next-generation iteration of the TI CC1312 that we use for receiving UAT (and soon, other sub-GHz aircraft tracking protocols), on the ADSBee 1090U.
At the beginning of 2026, we embarked on a design effort with these two MCUs, dubbing the combination “ADSBee 1421”, based on a concatenation of the constituent part numbers (TI CC13**14** and LR 20**21**). In line with our existing part conventions, a la ADSBee m1090, we added an “m” to the beginning of our part to denote that it would be built as a solder-down module, for easy integration into any custom PCB design. Thus, the ADSBee m1421 was born!
Feature Set
ADSBee m1421 features dual-band ADS-B reception (Mode S and UAT), including support for UAT uplink protocols (TIS-B traffic / FIS-B weather). Perfect for mass and power constrained embedded applications, m1421 weighs less than 2 grams, draws less than 60mW of power, and features an ultra-small form factor of 23.4 x 14.5mm x 2.7mm.
ADSBee m1421’s firmware and schematic are open source under a GPL v3 license. All aircraft position decoding and tracking logic is unified with our widely adopted ADSBee 1090 firmware, and available for building in cloud CI.
Output protocols supported by ADSBee m1421 include GDL90, MAVLINK1, MAVLINK2, Aircraft JSON, CSBee, and raw packets, with more protocols to come!
ADSBee m1421 is available in both **standard** and **NDAA-compliant** variants. The standard variant of ADSBee m1421 costs just $48 in single quantities, and even less at volume. Currently, our NDAA compliant variant is more expensive ($75), but we are actively working on increasing manufacturing capacity in the USA in order to bring our NDAA compliant variant to cost parity with our standard module version. We expect to reach cost parity around the end of this year (December 2026).
- !Image 2: ADSBee m1421 Module
- !Image 3: ADSBee m1421 module with dime for scale - front view.
- !Image 4: ADSBee m1421 module with dime for scale - rear view.
ADSBee m1421 Module
Price range: $48.00 through $75.00
High performance low power dual-band ADS-B receiver module
Quantity
Price
<1
$48.00
1 - 9
$48.00
10 - 99
$45.00
100 - 999
$42.00
1000+
$39.00
1 × ADSBee m1421 Module
$48.00
ADSBee m1421 Module quantity
Does the ADSBee 1421 family replace the ADSBee 1090 family?
Not really! ADSBee 1421 and ADSBee 1090 series receivers have very different architectures, and are good for different things. ADSBee 1421 uses the LR2021 for a highly integrated, low power Mode S receiver, but the LR2021 has some shortcomings compared to the discrete RF component + RP2040 PIO receiver architecture on ADSBee 1090. Most notably, in order to achieve satisfactory dynamic range (receiving both very close and very far away aircraft simultaneously), the LR2021 has to be tuned to listen to only one Mode S packet type; Downlink Format 17 aka. ADS-B. In short, it’s great at seeing where planes are, but you won’t receive squawk codes, and you will also receive fewer non-ADSB packets. This is generally not a cause for concern in detect and avoid applications, but can be a drawback for data gathering use cases. ADSBee m1421 features a high degree of configurability exposed through our firmware, so reception using the Mode S preamble (and therefore, reception of all Mode S packet types) is supported, but this results in poorer dynamic range (close-in aircraft can have poor reception).
Additionally, in its high-throughput configuration, Semtech LR2021 does not support per-packet timestamps nor RSSI. This can be a drawback for users attempting to use ADSBee m1421 for multilateration applications (tracking aircraft using a receiver array and time of arrival of each packet). We have some ideas in the back of our head about how MLAT might be added to our ADSBee 1421 firmware, but this still requires a good deal of tinkering and testing so we aren’t supporting it as an “out of the box” capability at this time.
**So, which one should you choose?**
Full-featured dual-band ADS-B with all the bells and whistles, where power / form factor / cost are secondary to device functionality. Built-in WiFi/Ethernet/USB connectivity: **ADSBee 1090**
Dual-band ADS-B sufficient for aircraft tracking, without MLAT timestamps / per-packet RSSI / non-DF17 packets, where power / form factor / cost are very important. UART interface only: **ADSBee 1421**
But wait, there’s more!
ADSBee m1421’s LR2021 is quite a capable radio, and not just when it’s used as a Mode S receiver! We’ve broken out the LR2021’s 2.4GHz frontend as a proper coplanar waveguide (labelled “LRHF” on the module), allowing customers to reuse the LR2021 as a mesh radio transmitter / receiver with LoRa and other supported protocols. ADSBee’s SYNC line allows an external host MCU to put the CC1314 to sleep within 25us, handing over full control of the LR2021. This gives you the best of both worlds in a flexible embedded application, as the CC1314 retains all aircraft data in its sleep state, so you can time-share between mesh radio and Mode S reception as needed. Note that ADSBee m1421 does not currently carry any module-level EMI certification, and it must only be used as a transmitter in compliance with local regulations.
Oscilloscope capture of the LR2021 RESET line (yellow) being released by m1421 after SYNC line (green) goes high, persisted across hundreds of handovers. ADSBee m1421 is “well clear” of the LR2021 by around 25us.
Neat! How can I get started with ADSBee 1421?
Plug and play mode: get a devkit!
If you want to get started right away with ADSBee 1421, you can pick up an ADSBee 1421 Developer Kit. This includes an ADSBee m1421 module soldered to our open source minimum form factor carrier board (forming what we call the ADSBee 1421). We built a separate RP2040 Zero board as a USB to Serial bridge and automatic device programmer, allowing you to easily communicate with your ADSBee 1421 and update its firmware from any computer (of course, the firmware source code for the programmer is also open source, so you are welcome to build your own, or easily add automatic firmware update capabilities to your own host microcontroller).
- !Image 6: ADSBee 1421 Developer Kit
Once an ADSBee 1421 is configured and has its firmware updated, you can plug it right in to any device that accepts ADS-B data over UART, like a drone flight controller or your own host MCU / CPU / whatever. We’ve built a set of open source software tools available at adsbee.aero that will let you connect to and configure your ADSBee 1421 devkit over USB serial, as well as view a live map of aircraft being received!
In the near future, we plan to offer ADSBee 1421 without a programmer, and without the SWD debug header attached. Stay tuned as we ramp up production!
Product design mode: build your own board!
We have quite a few customers who have already put ADSBee m1421 onto their own carrier board. Our KiCAD footprint files, symbols, and 3D models are freely available for ADSBee m1421, and our ADSBee 1421 minimum form factor carrier board reference design has all of its design files uploaded here, making it easy to get started with your own design.
For mass production use cases, ADSBee m1421 ships in trays of 50, making it easy for any contract manufacturer to place a module onto your own PCB design. The serial number label on top of every ADSBee m1421 is reflow safe and chemical resistant, and ADSBee m1421 can withstand up to two reflow passes without issue (so you can put it on the top or bottom of your PCB without any special precautions).
A tray of ADSBee m1421 modules, hot out of the oven! The trick is to remember to butter the tray before baking, or else they tend to stick.
For very high volume applications (purchase quantities above 1k, or estimated annual usage above 12k pcs/yr), we have additional volume pricing tiers available. Get in touch with me (john@pantsforbirds.com) and I’ll be happy to provide a custom quote.