FrSKY RX8R — redundancy bus receiver

Another new great product from FrSKY — RX8R receiver with inbuilt redundancy bus that is aimed to deliver some more reliability to the radio link signal.

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If you didn’t know yet, there are some products that FrSKY already make to get the most bulletproof radio signal by adding full-duplex relay with 2 parallel receivers together with doubling onboard batteries — Redundancy Bus and RB10.

But, if you don’t want to mess with such complicated setups, want to keep the weight of your model as low as you can, want to spend less yet having some compromise between a mere receiver and the full redundancy setup — RX8R is here for you.

Technical specifications:

• Band: 2.4GHz ACCST
• Channel: 16CH / 1-8ch from PWM
• 1-16ch from SBUS port
• S.Port
• RX IN port
• Two PCB antennas
• Full Range
• Full Telemetry
• Dimension: 46.25×26.6×14.2mm (L×W×H)
• Weight: 12.1g
• Operating Voltage Range: 4.0-10V
• Operating Current: 100mA@5V
• Firmware Upgradable
• Compatibility: FrSky radios/transmitter modules in D8/D16 mode

Those, who used X8R and X6R receivers before, would not find any difference in casing design, size and weight of the new product. What’s different — RX IN port instead or RSSI out and newly designed PCB antennas with no plastic covers. Moreover, you would follow the same steps to set it up as you’ve done with X8R and other jumper-equipped SBUS|PWM, S.Port receivers.

Despite the possibility of this receiver to work as a conventional X8R, the main goal of RX8R is to be used as master with some X-series, SBUS equipped receiver connected to RX IN port as a backup slave receiver. The only demand in such setup — slave receiver should be configured to no telemetry mode with PWM channels set to 9-16 (or else) output, if any, and master RX8R should be configured to 1-8PWM with telemetry. Than, you can connect SBUS output of RX8R to your flight model controller or ESC/servos to PWM 1-8 channels and connect other electronics to PWM channels of slave receiver, if any. Moreover, you have to configure failsafe values for 1-16 channels in master and 9-16 channels in slave to the desired positions.

You can bind both receivers to 1 radio module or bind the them separately to 2 separate modules ( in case if internal and external XJT are used — both switches of the exteranl module should be set to ON)

Such combination of 2 receivers would do the following:

1. RX8R, as a master, would give out SBUS channels 1-16 and PWM 1-8 as long as it stays online. With all telemetry and RSSI values.
2. When RX8R looses the signal, it would take the signal from slave receiver if it is still online with no interruption to all channels functionality. Unfortunately, you’d loose the telemetry.
3. In case if slave fails and master works — you’d loose PWM channels from the slave receiver (9 — 16) if any, and slave receiver would output failsafe values for those channels. But there is a telemetry from master to the radio.
4. In case if both receivers fail — they would both output corresponding failsafe values.

As you can see, the only real drawback of such setup is that you’d loose the telemetry and RSSI value whenever master goes offline. Even despite the fact that you model still controllable because slave’s receiver signal is relayed to the master.

Other combination would be to have 2 RX8R connected together. There are 2 options:

1. If you’d connect them with only one cable — system would act the same as in the previous description.
2. If you’d interconnect them with 2 cables in circles there would be 2 changes: one is that you no longer have SBUS channels because master SBUS port is busy with the cable, but, what is good is that you would have 16PWM channels system (1-8 from master and 9-16 from slave) that would work at any time, no matter which one of the receivers goes offline. Still, slave should be configured to have no telemetry, thus, again, if master fails all 16 channels work but no RSSI and other values….

Binding 2 interconnected RX8R (with 2 cables) to 2 separate radio modules would bring even more reliability and give you the most out of such system setup.

I have conducted the test to check the first situation: 1 RX8R as master and 1 X8R as a slave. No problems here (look at the video review). They work as described, making the radio link more reliable especially if receivers are situated at different locations on the model to get the most out of such kind of diversity or redundancy setup.

I have noticed that right at the time when RX8R master looses signal the servo connected to its PWM output has a momentary freeze or uneven movement and then continues to work smoothly. This is due to the signal overtake (relay) time period when master fails and slave starts to output its signal is about 900ms. In case if you want much faster relay time — you should use RB10 instead. I have reported this to FrSKY and hope that they would be able to reduce the lag.

FrSKY has updated RX8R FW and now it has no visible lag of master to slave switching at all!!! Excellent!!! Newer FW is available by this LINK.

I don’t have 2 RX8R to check the other described situations, but I don’t see why it shouldn’t work.

Therefore, I can conclude that whenever someone wants to reinforce or defend his radio link with the lowest possible cost, weight and amount of wiring — he should consider having one or even two RX8R receivers with redundancy bus feature.

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Stay tuned, more reviews are coming!!!