iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Hackaday Podcast Episode 391 links three maker-and-science themes: experimental software-defined radio on ESP32 chips, a project that modernizes a vintage pager, and a “Bugs on Mars” segment whose specific subject is not identified by the episode information currently available. The ESP32 work is not a drop-in replacement for a universal SDR, but it does expose raw radio samples on selected chips and has progressed from receiving toward experimental transmission. The pager project shows how an ESP32-C3 can replace an old pager’s radio while preserving its original processor, display, and alert behavior.
What Episode 391 covers
The title names three separate stories rather than one connected project. The first concerns access to in-phase/quadrature (I/Q) radio samples from parts of the ESP32 family. The second is the ESPager conversion, which gives a first-generation Motorola Advisor-style pager a modern network interface. The final title phrase, “Bugs on Mars,” is not specific enough to establish which mission, rover, biological question, or reported discovery the segment discusses. No episode date, show notes, quotation, or segment timestamps are confirmed here, so those details should not be inferred from the title alone.
What ESP32 SDR means
Software-defined radio (SDR) moves some radio processing into software. Instead of exposing only decoded Wi-Fi or Bluetooth packets, an SDR can provide streams of sampled signal data. Software can then inspect spectra, demodulate signals, or develop experimental protocols.
Free tools Windows power users keep installed
One-click scans. No signup required.
Several ESP32-family radios have an undocumented or experimental path to raw I/Q samples. The work is concentrated around the 2.4 GHz Wi-Fi band; some ESP32 variants also reach 5 GHz. The exact chip, firmware, sample path, and host software determine what is possible. “ESP32 SDR” therefore describes an emerging technique, not a single standardized product or firmware feature.
#1 Best Overall
- Turn your computer, phone or tablet into a radio scanner/ham radio receiver that can receive nearly all RF signals! Compatible with Windows, Mac OS, Linux, and Android
- NESDR SMArt RTL-SDR v5 can be used for the reception of broadcast AM radio, broadcast FM radio, shortwave radio, CB radio, public security radio, trunked radio, air traffic control, ACARS (plane-ground communications), ADS-B (plane tracking), AIS (ship tracking), POCSAG (pagers), NOAA and GOES weather satellites (weather images), weather balloons, radiosondes, DAB radio, DVB-T video, Inmarsat, Iridium, and so much more!
- The best-performing low-cost RTL-SDR available anywhere! Compared with RTL-SDR v3, HF SNR is improved by up to 15dB, VHF & UHF SNR is improved by up to 6dB, tuning accuracy is improved by an average of 4x, and the frequency range is expanded all the way down to 100kHz
- v5 has a frequency capability of 100kHz to 1.75GHz and up to 3.2MHz of instantaneous bandwidth. HF reception below 25MHz is accomplished with direct sampling and requires a suitable antenna. We recommend using a Balun One Nine to make a DIY long wire or dipole antenna (sold separately, product ID B08HGSYB7R or B00R09WHT6)
- Though the direct sampling implementation of NESDR SMArt v5 is much better than any other RTL-SDR, we still recommend using an upconverter like the Ham It Up for a more fulfilling HF experience (sold separately, product ID B076CYK8XZ)
Receive and transmit capability
Early demonstrations focused on receiving samples. A later firmware update showed experimental transmission as well, including a Hellschreiber exchange between ESP32 boards. That demonstration indicates that selected hardware and firmware can generate a signal, but it does not make every ESP32 board a general-purpose transmitter. Regulatory limits, antenna design, calibration, occupied bandwidth, and the particular radio peripheral still matter.
How it differs from an RTL-SDR setup
| Aspect | ESP32 SDR work | Typical RTL-SDR approach |
|---|---|---|
| Frequency coverage | Primarily 2.4 GHz on the demonstrated work; some ESP32 variants also support 5 GHz | Broad receive coverage depending on the specific USB tuner and front end |
| Radio samples | Access relies on an undocumented or experimental chip path and matching firmware | Established USB-SDR software ecosystem and documented device interfaces |
| Transmit | Experimental firmware has demonstrated transmission, including Hellschreiber | Common RTL-SDR USB receivers are receive-only |
| Host requirements | Usually an ESP32 board plus firmware and a computer or network service to process samples | USB receiver, antenna, drivers, and SDR software on the host computer |
| Maturity | Developing; support varies by ESP32 family member | More mature for general receive experimentation |
The practical takeaway is that an ESP32 can be used as an SDR in a limited, experimental sense. It is useful for learning about I/Q data and for exploring signals in the bands its radio supports, but it should not be treated as a low-frequency, all-band receiver. Sample rate, data format, synchronization, and host-processing requirements depend on the implementation and are not uniform across ESP32 models.
Rank #2
- Included: Nooelec USB dongle & antenna
- RTL2832U interface IC & R820T tuner IC on USB dongle
- These are custom USB devices tuned for SDR and include much better components than generics
- Full 1-year warranty & installation support available!
How the ESPager brings an old pager back
The ESPager project by Corey Harding converts a first-generation Motorola Advisor, or another pager that supports POCSAG or GSC, by replacing the pager’s radio module with an ESP32-C3. The original pager processor, display, and alert behavior remain in place. The ESP32-C3 becomes the modern communications path rather than replacing the entire pager electronics.
Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Messages can be submitted through a web interface. An Asterisk or FreePBX installation can also use the project’s web API to trigger a callback number, making the pager a compact notification endpoint for a self-hosted phone system.
Rank #3
- Turn your computer, phone or tablet into a radio scanner/ham radio receiver that can receive nearly all RF signals! Compatible with Windows, Mac OS, Linux, and Android
- NESDR SMArt RTL-SDR v5 can be used for the reception of broadcast AM radio, broadcast FM radio, shortwave radio, CB radio, public security radio, trunked radio, air traffic control, ACARS (plane-ground communications), ADS-B (plane tracking), AIS (ship tracking), POCSAG (pagers), NOAA and GOES weather satellites (weather images), weather balloons, radiosondes, DAB radio, DVB-T video, Inmarsat, Iridium, and so much more!
- The best-performing low-cost RTL-SDR available anywhere! Compared with RTL-SDR v3, HF SNR is improved by up to 15dB, VHF & UHF SNR is improved by up to 6dB, tuning accuracy is improved by an average of 4x, and the frequency range is expanded all the way down to 100kHz
- v5 has a frequency capability of 100kHz to 1.75GHz and up to 3.2MHz of instantaneous bandwidth. HF reception below 25MHz is accomplished with direct sampling and requires a suitable antenna. We recommend using a Balun One Nine to make a DIY long wire or dipole antenna (sold separately, product ID B08HGSYB7R or B00R09WHT6)
- Though the direct sampling implementation of NESDR SMArt v5 is much better than any other RTL-SDR, we still recommend using an upconverter like the Ham It Up for a more fulfilling HF experience (sold separately, product ID B076CYK8XZ)
Parts identified for the conversion
| Part | Purpose or qualification |
|---|---|
| Seeed Studio XIAO ESP32-C3 or generic ESP32-C3 SuperMini | Replacement communications controller; radio and firmware compatibility must be checked |
| 3.7 V 10440 rechargeable battery | Power source sized for the pager enclosure; physical fit and protection are essential |
| Small 1.8 V LDO or buck converter | Provides the voltage rail required by the pager electronics |
| 1S Li-ion battery-management/protection board | Provides charging and protection functions for the single-cell battery |
| Wire and cloth harness tape | Used for internal wiring and securing the retrofit |
| UART adapter | Provides serial access during setup or diagnostics |
| 3D-printed TPU programming adapter | Mechanical aid for connecting the programming interface |
| Dupont jumper wires | Temporary or service connections during wiring and programming |
The project does not establish a universal parts fit for every pager. Before buying anything, identify the pager’s supported protocol, battery compartment dimensions, voltage rail, connector pinout, and programming access. A pager that lacks POCSAG or GSC support, or one with a different internal power architecture, may require a different design.
A safe build sequence
- Verify the donor pager. Confirm the model, protocol support, display and alert operation, and the voltage required by the original radio and processor.
- Document the original wiring. Photograph connectors and record pin functions before removing the radio module. Do not assume two pager models share the same pinout.
- Plan power first. Match the 3.7 V cell, protection board, and 1.8 V regulator or buck converter to the pager’s measured requirements. Keep the battery-protection circuit in the design.
- Fit the ESP32-C3. A XIAO ESP32-C3 or compatible SuperMini must fit mechanically and expose the serial and radio connections needed by the firmware.
- Program and test outside the case. Use the UART adapter and TPU programming adapter, then verify boot, message reception, display output, and alert behavior with the battery disconnected or current-limited during initial checks.
- Integrate the web path. Configure the project’s web interface, and only then connect any Asterisk or FreePBX automation to its callback API.
- Insulate and secure the assembly. Use suitable wire routing and cloth harness tape, prevent shorts, and check that the battery cannot be crushed by the enclosure.
The exact firmware commands, API endpoint format, and wiring map are project-specific; they should be taken from the ESPager project documentation for the chosen donor pager rather than guessed from the component list.
Rank #4
- Includes 1x RTL-SDR Blog brand R860 RTL2832U 1PPM TCXO HF Bias Tee SMA Dongle (V3) (Dongle Only)
- Several improvements over other brands including use of the R860 tuner, improved component tolerances, a 1 PPM temperature compensated oscillator (TCXO), SMA F connector, aluminum shielded case with thermal pad for passive cooling, and an activatable bias tee circuit.
- Can tune from 500 kHz to 1.7 GHz and has up to 3.2 MHz of instantaneous bandwidth (2.4 MHz stable). (HF reception below 24 MHz in direct sampling mode with reduced performance). Please note RTL-SDR dongles are RX only.
- Please follow the quickstart guide linked in the included the manual for installation of the drivers and free software. Please feel free to contact us via Amazon messaging for technical support - we're happy to help
What “Bugs on Mars” means here
The phrase is not enough to identify a factual Mars story. It could refer to biological contamination, software defects, rover hardware faults, or a metaphor in the episode, but none of those interpretations is established by the title alone. No specific organism, mission, rover, experiment, statistic, or quotation should be attributed to Episode 391 until official show notes identify the segment. Readers looking for a definitive explanation should treat the phrase as an unresolved segment label, not evidence that insects or other life have been found on Mars.
Who should try these projects?
- Choose the ESP32 SDR work if you already have a supported ESP32 variant and want to study I/Q samples in the 2.4 GHz or, where supported, 5 GHz range.
- Choose the ESPager conversion if you have a compatible pager and are comfortable tracing legacy wiring, regulating Li-ion power, and programming an ESP32-C3.
- Use a conventional RTL-SDR USB receiver when your priority is a mature receive-only SDR workflow across a wider range of frequencies rather than ESP32 experimentation.
Neither project is a guaranteed plug-and-play build. The ESP32 route depends on chip and firmware support, while the pager route depends on the donor model’s protocol, voltage, dimensions, and accessible connections.
Quick Recap
Best Value
- NEW RTL-SDR FM+DAB USB DVB-T Dongle DVB-T STICK 100% REAL WITH RTL2832U+R820T2! The R820T upgrade version!
- Use the Rafael Micro's R820T2 offer possible range 25 - 1700 MHz
- The RTL2832U outputs 8-bit I/Q-samples, and the highest theoretically possible sample-rate is 3.2 MS/s,
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
