RF401A 900 MHz Spread-Spectrum Radio


The RF401A is a 900 MHz radio designed for license-free use in several countries, including the United States and Canada. It provides a hassle-free way to create long-distance wireless links between your computer, data loggers, and measurement devices. The RF401A has a 910 to 918 MHz operating-frequency range and a configurable transmit-power output of 5 to 250 mW.

Campbell Scientific recommends the RF401A radios for existing installations that require compatibility with products such as the RF401, CR206X, CR211X, AVW206, and AVW211. For new installations, Campbell Scientific recommends using the RF407 or RF451.

Note: The image depicts the RF401A with an attached antenna. The antenna is sold separately.

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Benefits and Features

  • Rugged, low-cost transceivers
  • Can be used in the field as a transceiver or in the office as the base station
  • Individual FCC license not required
  • Transmits up to one mile with omnidirectional antenna; up to 10 miles with higher gain directional antennas at ideal conditions
  • Settings stored in non-volatile memory
  • Frequency-hops over 25 channels avoids interference from other spread spectrum radios
  • Optional extended temperature testing
  • Faster communication due to elimination of some small "link state packets"
  • Ability to have stand-alone RF router/repeaters (up to 8 repeaters)
  • Greater immunity to interference and RF collisions by using RF retries
  • Reduced power consumption by the data logger, as the radios perform "packet address filtering"
  • Designed for use in PakBus networks
  • Built-in setup menus allow access to advanced functionality


Detailed Description

The RF401A is a frequency hopping spread spectrum radio designed for 900 MHz license-free ISM band operation. It has a 910 to 918 MHz operating-frequency range and a configurable transmit power output of 5 to 250 mW. It provides one of three selectable active connections including CS I/O, RS-232, and USB. It has a reverse polarity SMA (RPSMA) antenna jack connection. It is over the air compatible with legacy 9XStream products including the RF400, RF401, RF430, CR205, CR206(X), and AVW206.



Radio Type Frequency Hopping Spread Spectrum (FHSS)
Frequency 910 to 918 MHz
Country Used In US, Canada
Transmission Distance
  • -Note- Transmission distance assumes line-of-sight and appropriate antenna. Line-of-sight obstructions, RF interference, and antenna type will affect transmission distance.
  • Up to 1.61 km (1 mi) with omnidirectional antenna; up to 16.09 km (10 mi) with higher-gain directional antennas at ideal conditions
Power Output 5 to 250 mW (software-selectable)
Receiver Sensitivity -109 dBm (Campbell Scientific protocols will issue retries wherever a bit error occurs.)
Channel Capacity 7 hop sequences share 25 frequencies.
RF Throughput Data Rate 9.6 kbps
Data Rate 10 kbps
Antenna Connector Reverse Polarity SMA (RPSMA) jack
LEDs Power on, Tx, Rx, diagnostics
RS-232 Baud Rate 1200 to 115200 bps
CS I/O Modes SDC 7, 8, 10, 11, and ME master
Average Current Drain
  • Transmit: < 80 mA (250 mW TX power)
  • Stand-by: < 0.5 mA (depending on power-saving mode)
  • Receive: 15 mA
Power 9 to 16 Vdc
Power Connector 2.5 mm DC power jack
Operating Temperature Range
  • -25° to +50°C (standard)
  • -40° to +85°C (extended)
Communication Ports
  • RS-232 9 pin D female
  • CS I/O 9 pin D male
  • USB Type B jack
Service Requirements Shares frequency with other devices. Must not cause harmful interference to licensed radios. Requires line-of-sight.
Dimensions 11.1 x 6.9 x 2.7 cm (4.4 x 2.7 x 1.1 in.)
Dimension are from the tip of antenna connector to other side of case, and from the bottom of case to the top of DB9 connector jack screw. The width includes the thickness of the screw heads on the screws that hold the case together.
  • 136 g (4.8 oz) without "Ships With" items
  • 283.5 g (10 oz) with "Ships With" items


United States (FCC Part 15.247) MCQ-XB900HP
Industry Canada (IC) 1846A-XB900HP



The RF401A is over-the-air compatible with the RF401, RF430, CR206, CR206X, and AVW206. 

Other Radios

The RF401A is also compatible with the RF400 and CR205, but the communication protocol must be set to transparent. Also, if RF400 and RF401A radios will be in the same RF proximity, do not use 28, 44, 52, 56, or 60 for the RF400 Net Address. RF400 radios with Net Addresses of 28, 44, 52, and 56 interfere with RF401A radios with Net Addresses of 0, 1, 2, and 3, respectively. The RF400 Net Address of 60 interferes with all RF401A Net Addresses.

Campbell Scientific does not recommend using the RF401A in networks containing FGR-115 or RF450 radios.

Transparent and PakBus Protocols

Do not mix RF401A radios using the Transparent protocol setting with RF401A, RF401, RF430, CR206(X), or AVW206 devices using a PakBus protocol setting. This will produce RF traffic without any RF communications. However radios with the PakBus Aware and PakBus Node settings can coexist in the same network.

Data Logger Considerations

Data Logger RS-232 CS I/O
CR300 *
Mixed-array data loggers **

*Use a 18663 null modem cable.
**It is possible to connect a mixed-array data logger (e.g., CR10, CR10X, CR23X, 21X, CR7) by using an SC932A or SC105 between the data logger's CS I/O port and the RF401A's RS-232 port.


RF401A Series OS v.05 (438 KB) 22-07-2015

Current RF401A and RF411A firmware. Requires the Device Configuration Utility.

View Revision History

Device Configuration Utility v.2.29 (54 MB) 15-11-2023

A software utility used to download operating systems and set up Campbell Scientific hardware. Also will update PakBus Graph and the Network Planner if they have been installed previously by another Campbell Scientific software package.

Supported Operating Systems:

Windows 11 or 10 (Both 32 and 64 bit)

View Revision History

FAQs for

Number of FAQs related to RF401A: 20

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  1. If you have an RF401/RF401A/RF407/RF411A/RF412/RF427 network that has been working reliably for months and then suddenly fails with intermittent data collection, the site hasn’t changed, and there hasn’t been any new construction in the area, the issue may be caused by a piece of new equipment that was installed on the job site during the COVID-19 pandemic.

    Because of the COVID-19 pandemic, some job sites implemented badge sensor technology for contact tracing and social distancing. Often, these devices operate on Wi-Fi or Bluetooth, but some of them operate in the 900 MHz range, which is used by our spread-spectrum radios and can, therefore, cause interference. Fortunately, you can resolve this issue using radio channel masking.

    The following outlines the steps that were taken to correct this issue in one specific example:

    1. The datasheet for the COVID-19 badge equipment was found and reviewed to determine that it was operating from 915 to 926 MHz.
    2. The manual for the RF407 900 MHz Spread-Spectrum Radio was reviewed. The manual reported the frequency for bit 0 and bit 63 as 902.4 MHz and 927.6 MHz with a channel spacing of 400 KHz.
    3. Using a mathematical calculation, it was determined that masking channels 31 to 60 would block off 914.8 MHz up to 926.4 MHz.
    4. Entering 0000000000000000000000000000001111111111111111111111111111110000 into a binary-to-hex converter provided a mask of FFFFFFFC0000000F. (The default Calculator app provided by Windows has a Programmer option listed under the hamburger menu that you can use for the conversion.)

      The Programmer option listed on the calculator

      The selected Programmer option on the calculator

    5. The mask of FFFFFFFC0000000F was used in the Radio Channel Mask setting, and the radio network returned to providing reliable operation.

    For more detailed information about using radio channel masking, refer to your spread-spectrum radio manual. For example, the RF407-Series manual has a section devoted to this topic.

  2. There are many cavity- and notch-type filters available from third-party manufacturers.

  3. There is a good chance that they would. However, the RF401A radios have been designed to work with Campbell Scientific data loggers. There are more generic spread-spectrum radios (off the shelf) that are designed to work in this type of configuration.

  4. The RF401A and RF411A have distinct advantages over their predecessors, including greater maximum transmit power, lower average power consumption, improved packaging, and the inclusion of USB, RS-232, and CS I/O on a single device.

    • The RF401A is compatible with all of its RF400-series radio predecessors, including the RF400, RF401, and RF430. The RF401A is also compatible with the CR205, CR206X, and AVW206.
    • The RF411A is compatible with all of its RF400-series radio predecessors, including the RF410, RF411, and RF431. The RF411A is also compatible with the CR210, CR211X, and AVW211. 
  5. The COM220 and the RF401A can coexist on the CS I/O terminal, provided that they are assigned two different SDC addresses.

  6. Yes, as do all radios. Adjacent radio equipment operating in the same frequency range can cause interference.

  7. Use of the callback feature is handled under program control by the data logger and is not affected by the RF401A.

  8. Yes. The RF401A protocol needs to be set to transparent, which will communicate with the RF400 devices. However, if there are RF400 devices that are set to addresses of 28, 44, 52, 56, or 60, they must be changed when the RF401A radios are added to the network.

  9. The RF401A can be powered either from a 12 Vdc source via the field power cable, or from a data logger via the CS I/O port.