Another feature of the R9 Slim+ long range receiver is its ability to output inverted S.BUS & S.PORT signals

In previous articles, we have discussed the frsky R9m system and R9m Lite, two remote systems created by frsky to overcome the shortcomings of the 2.4GHz system, such as the lack of penetration barriers and the range of systems below 900MHz. In this article, we will examine the R9m RC link system of the frsky R9 slim + long range receiver to see if it is suitable for use in your UAV and other buildings.

Why R9 slim +?

The frsky R9 slim + has been created by frsky to compete with the team black sheep cross fire Mini receiver. Since the full-size frsky R9 receiver is too large for the Mini Quad, the R9 is slim. You can get R9 slim from horusrc

Features of ultra thin sky fr 9 receiver

915MHz (non EU version) / 868mhz (EU version)

Optimized performance

Detachable IPEX antenna x 2

Small size, easy to install

Low delay, high precision

Support redundancy

Full range telemetry and intelligent port function

Battery voltage detection

Analog or digital RSSI output via pins or channels

Support inverted s.bus and inverted s.port (frsky has reversed its signal, so this is the basic non inverted signal) to make it compatible with F1, F3 and F4 flight controllers.

PCB protection in conformal coating process

The frsky R9 slim + has antenna diversity, which means it has two antennas for reception. This improves the range compared to a single antenna. The antenna connector is an IPEX style detachable antenna, so it is easier to remove the antenna if you damage it.

Another notable feature of R9 slim + is that it can output reverse s.bus and s.port signals. By default, frsky outputs the reverse signal on both s.bus and s.port, which is why we need to use the inverter of the F1 / F3 / F4 processor on the flight controller to decode the reverse signal. But with R9 slim +, forsky is generous enough to include reverse signals (double reverse so technically practical non reverse signals!) for s.bus and s.port signals.

In this way, all your flight controllers, whether incompatible with the reverse signal, will work well with this receiver; even the s.port can work normally, providing full telemetry!

Specification R9 slim+

Dimensions: 32 * 13.5 * 5mm

Total weight: 4.3G (with antenna)

Number of channels:

Non EU version: 6 / 16CH (telemetry)

EU version: 6 / 8CH (telemetry) / 6 / 16CH (telemetry) / 6 / 16CH (no telemetry)

With RSSI output: analog 0 ~ 3.3V

Working voltage range: DC 3.5V ~ 12.6V (3S lithium battery)

Current operation: 100 ma@5v

Operating range: 10km and above

Firmware update

Compatible: R9m and R9m Lite

Shape factor and pin lead

The R9 slim + has a narrow design and narrow height, which makes it suitable for mini four axis aircraft.

Since the receiver also has 6 PWM channels as well, it makes it easy to use airplanes and fixed wings, even RC cars, if you want to do remote with it. I mean, who doesn’t want to drive for miles with a FPV? FPV makes everything more interesting

The top of the receiver contains a bind button to bind the receiver to the transmitter of your choice; any frsky Taranis radio with a R9m or R9m Lite (or pro) transmitter module will work with the receiver.

There are also two LEDs next to the bind button to show the status of the receiver. One green and one red LED. The antenna connector is on the right side of the receiver.

The one on the left is where you can find connector 1. The output and input of the connector are as follows:



– s。 Bus input (for redundancy)

– s。 To leave (to a flight controller) by bus

-RSSI output (0 to 3.3V analog output)




The bottom is flat except for the second joint. The connector has the following pins:


Interactive (TX)

-CH5 (RX)






As long as the output and shape of the receiver are taken into account, these are the only points to be noted.

The new frsky R9 slim + long range receiver provides OTA support through the new frsky access protocol, as well as more functions.

In this article, we’ve seen about the frsky R9 slim + receiver, its usage, tip and other factors, and how it works with the transmitter module of the R9m system.

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