FRSKY is the most popular quadcopter digital radio protocol because of regular development and the availability of low cost highly effectiver receivers meaning that every quad you own can have it's own receiver without always changing in an out. A benefit to this means is that each quad can have a customised reviever for what that specific quad needs - long range with diversity and redundancy, full telemetry, the new f-port protocol, pwm output for servos or just the smallest and lightest receiver possible.
In terms of the latter, micro quad builders generally need the smallest and lightest receiver possible and up until recently this has been the FRSKY XM. This is a receiver that weights just over 1g and measures 15x10x3.5mm. Silly as it sounds but what if this is too big? In the case of my ultralight X2 Eyas (rotorbuilds build details here) this was exactly the case. The Full Speed FrSky-Nano 2.4GHz 8CH Receiver is the smallest FRSKY receiver you'll find - it is approximately half the size and weight of the XM, coming in at just 0.5g and measuring 12mm x 10mm x 2.5mm. It's worth mentioning that this is the same FullspeedRC that came up with the Leader 120 and the TX200 VTX - strong credentials in the micro quadcopter space. It certainly helps these models are designed and tested by Lewis who is a micro pilot himself rather than just a marketer.
Binding (from FullspeedRC.com)
1. Select D8 mode on Frsky remote control. Hold the bind key on Frsky-Nano receiver and connect the battery, then the receiver's red light will be always on.
2. Select the BIND mode on remote control , the Frsky-Nano receiver's blue light will flash slowly and the red light will be always on which means bind complete.
3.Enter: set sbus_inversion = off (set serialrx_inverted = on if your FC is BF3.3 or newer)on BF CLI and save.
4. Repower the Frsky-Nano receiver . The red light on it will flash very quickly which means it receives the singal from remote control
I did know that this nano receiver sent RSSI over an auxilliary channel but it was a nice surprise to find this set up out of the box unlike every XM, XM plus, XRS, RXSR receiver I've ever come across. Better still was that it was set to Aux 5 (channel 9) meaning all 4 auxilliary channels are available for control. With betaflight set to recognise Aux 5 as RSSI it is easy to add to betafilght OSD and display RSSI which is important as i'll get to shortly.
For a defined digital protocol (in this case SBUS) the only parameter to discuss in receiver performance is range. I'll be the first to admit that my antenna placement is not great but the range was probably a little less that I was expecting. When I ventured more than about 100m away in a residential neighbourhood I started dropping to about 30 RSSI. Given this was an ultralight build with an all in one camera/VTX I was not concerned beacuse this is about the realistic range of my 25mW vtx anyway. The good news is that with RSSI displayed in the OSD you at least have the tool to manage this.
I think the range is a fair limitation for this receiver. I see it being used for ultralight brushless micros or tiny whoops where you mostly fly in close proximity to yourself. It's also worth reiterating that with better pacement of the receiver/antenna I should be able to get much better range if I needed it.