Review: Frsky R-XSR Receiver - The New "Best" Mini Quad RX?

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The Frsky R-XSR receiver is the smallest RX that can do 16 channel SBUS and SmartPort telemetry. It’s the go-to option now and replaces the XSR or X4R-SB for Frsky TX users who own a Frsky transmitters such as the X9D and QX7.

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You can purchase the Frsky R-XSR radio receiver from

• Banggood
• Amazon
• GetFPV
• HorusRC

Why you want to buy the R-XSR?

When you ask an experienced mini quad pilot using Frsky TX, “What’s the best Frsky receiver?” The answer is probably going to be “XSR” or “X4R-SB”. But the new R-XSR might be the new answer to that question.

Nowadays, the following features have become the standard for Frsky mini quad receivers:

• SBUS
• SmartPort telemetry
• Diversity Antennas (full range)
• Small and light weight

And the R-XSR ticks all the boxes yet it’s tiny compared to the XSR and X4R. It’s basically just the XSR but in a much smaller form factor.

It comes with IPEX antenna connectors so you if damage the antenna you can easily buy a new one and replace it.

Here is a comparison table between these RX’s.

Product Page	R-XSR	XSR	X4R-SB	XM+
Price (Oct 2017)	$25	$17	$29	$13
Size (mm)	16 x 11 x 5.4	26 x 19.2 x 5	40 x 22.5 x 6	21.5 x 12 x 3.5
Weight	1.5g	3.8g	5.8g	1.6g
Voltage	4V-10V	4V-10V	4V-10V	3.7V-10V
Current	70mA@5V	100mA@5V	100mA@5V	30mA@5V
SBUS ?	Yes	Yes	Yes	Yes
S.Port ?	Yes	Yes	Yes	No

It might even replace tiny receivers like the XM+ RX which were only released earlier this year.

Check out this post to find out aobut other Frsky RX for mini quads.

New Feature – Receiver Redundancy

When I read through the manual of the R-XSR RX, I found it has a new and interesting feature called “Receiver Redundancy”. If you look at the pin-out of the R-XSR, you might realize there are the SBUS_IN and SBUS_OUT ports.

What it does, is allowing you to connect a separate SBUS receiver to the “SBUS_IN” of the R-XSR. When the R-XSR fails and loses signal, the other receiver will try to take over.

But not both receivers are connected to the same Taranis internal TX module, you will also need a separate TX module such as the XJT module plugged in to the TX module bay on the back of your Taranis.

So there would be two separate connections. You can even use a separate Taranis TX rather than an XJT module if you want.

For example you could use the XM+ and connect it up to your R-XSR like this:

In my opinion this is quite a cool idea that could save your quad from hardware failure and bad signals, but I don’t see it being used by ordinary pilots and racers due to the complexity of the setup and the cost for additional equipment.

Why you might not want to buy the R-XSR, yet?

However, the new R-XSR is not perfect and you might not want it get it, just yet.

As we speak, LUA script is still not compatible yet (which allows you to change PID, rates, VTX settings etc from your Taranis). As far as we know this should be fixed soon with a firmware update. Update (Oct 9th, 2017): Frsky has just fixed the issue with LUA script, make sure you update your R-XSR with this latest firmware. Here is the instruction how to flash Frsky receiver firmware.

The second issue is finding the uninverted Smart Port signal. It is possible to get the uninverted S.Port signal on the board just like other receivers as shown in this tutorial, but the pin is so tiny it’s quite challenging to solder on.

Finally, the antennas are not optimal. I wish they just follow the XSR and solder the antennas directly to the receiver rather than using those fragile iPEX connectors which are only designed for a few mating cycles.

And just like the XSR, the R-XSR is using “1/5 wavelength” antennas, which means the antenna elements shorter than the original X4R-SB of 1/4 wavelength antennas. Many people including have reported range issues and complained about it to Frsky. We’ve been told the reason behind this design is to reduce the chance of a prop strike, which doesn’t make much sense to be honest. However if you are having range issue, you can simply strip the antenna shielding to extend the antenna element and experiment until you find your desirable length.

If none of these issues bother you, then you should definitely get it while they are still in stock. But because of the release of the new RX, the old XSR prices have dropped considerably to only about $17.

Manual

Update (Oct 2017)

Frsky finally listened and might release a version of the R-XSR RX in the near future that has a separate, uninverted SmartPort output. This is great news for those who are running an F4 board that doesn’t have an inverted UART for S.Port signal. We don’t know when this will be available yet.

Update (13 Oct 2017)

Frsky has just released a new revision of the R-XSR, that has added the “uninverted SBUS” and “uninverted Smart Port” solder pads. As far as I know, they won’t release a version with just the uninverted signals, so this is it. But still it’s much easier to solder to.

Here is an image provided by Frsky – the “B” pad is uninverted SBUS, “P” pad is uninverted Smart Port.

Antenna Replacement

The R-XSR uses smaller IPEX connector for the antennas than the original X4R-SB receiver, they are called “IPEX 4th Generation”. Be careful when shopping around for antenna replacement.

I found this on Amazon (US), only $12 for 20! http://amzn.to/2EVI6c0

For international buyers, this is the only source I can find so far: http://bit.ly/2H42gRy

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