FrSky RX4R. The FrSky RX4R is an autonomous receiver that features 4 PWM outputs with low latency. The FrSky RX4R has all the previous functions of its antecessor, the X4R, but this new model is much smaller and lighter (Dimensions: 18×17×7mm (L×W×H) & Weight: 2g/ 2.4g (with two antennas)), and it can reduce the output latency, up to 9ms less than the X4R.

In addition to this, the FrSky RX4R also supports the redundancy function, or the master and slave receivers. The master receiver receives SBUS signal from the slave receiver. This means you can add another receiver as a back-up in case the first one fails.

Finally, the FrSky RX4R receiver is compatible with ACCST protocol, and with ACCESS protocol, that means that it can be re-bound at any time without accessing the F/S button once it is registered to an ACCESS radio when the receiver is flashed with the ACCESS firmware.

RX4R Features

Apart from including the RX4R receiver, the package also comes with two cables for connection, a jumper set and a detailed manual with the operation of the receiver.

Channels and Compatibility: The RX4R is a 4 PWM channels receiver with the features of the previous model, the ones of the X4R as we talked before. The PWM protocol is highly precise and it has low latency;

ACCST | 9ms (HS—High Speed Mode)/18ms (FS—Normal Speed Mode)

 ACCESS | 7ms (HS—High Speed Mode)/20ms (FS—Normal Speed Mode).

 For this a reason, the FrSky RX4R is the most convenient receiver for a fixed wing or similar.

We can also choose to use it in 16-channel mode with telemetry with the SBUS protocol. The binding of the FrSky RX4R has to be done in ACCST D16 mode, so it is compatible with a Taranis radio, an Horus radio or with an external XJT module. But if you have a radio system that can use ACCESS protocol, you can also bind it in ACCESS mode if the receiver has the ACCESS firmware installed.

Operating Range: RX4R and the whole RX-line has a 40% increased operating range compared to the previous X series receivers, such as X4R. Whereas the previous model had an operating range up to 1.5km, this new receiver has an operating range of more than 2Km.

Other Characteristics

  • Lower power consumption, around 100mA when it is powered to 5V.
  • Redundancy function supported as mentioned before.
  • PCB protection with conformal coating craftwork.
  • RSSI signal compatibility.

If the FrSky RX4R bind button is heled for about 5 seconds, the RSSI signal gets automatically in channel 16 so there is no need to do any configuration on the radio controller.

  • 2 detachable antennas with an IPEX 4 connector.

The antennas are 15cm long and made of stronger cables, and the radiating segment is about 33mm long.

Wiring Diagram

The pinout of the RX4R consists of 7 soldering pads with one function each.

  1. Inverted Smart Port. In the back side of the board to get telemetry on F4 flight controllers without bi-directional inverter.
  2. Ground
  3. Positive. Voltage input around 3.5V to 10V.
  4. Smart Port. For telemetry.
  5. AIN2. For battery voltage detection, this is the easiest way in order to know the voltage of the battery.
  6. SBUS_OUT. To output the signal received to the aircraft.
  7. SBUS_IN. A SBUS signal input to connect a redundant receiver.

1-4: PWM Channels. /+: Voltage Output. /-: Ground.

Bind – Failsafe

To make long story short, these procedures are the same that are taken on other receivers. Starting from the binding of the RX4R, it is as simple as selecting D16 mode for ACCST and ACCESS mode for ACCESS protocol, this is found on the 2-tab, SETUP, of the menu, on Internal RF in the mode selection. After that, go to BND and press ENTER, choose between Ch1-8/Ch9-16 and Telem ON/OFF according to your preferences for the RX4R.

If you hear a beep coming from your radio, then press the button on the receiver and power it on, once is turned on, release the button, click ENTER on the Taranis, and turn off your RX4R receiver, turn it on again to check if it has bound successfully. If the status led holds green, this means that the receiver has been correctly bound. If your status led doesn’t hold green, check the procedure again or the firmware compatibilities between your RX4R receiver and your radio.

To set the failsafe on the RX4R, just go to the Failsafe selection in Internal RF of your RC controller and select the Failsafe feature you desire.


In conclusion, the advantages of this receiver among other receivers are its small size and weight, the improved range of around 40% and improved latency in comparison with other receiver series, but also the FrSky RX4R receiver is easier to setup than ever. It also includes redundancy function, PCB protection with conformal coating craftwork and RSSI signal compatibility.