My recommendation is to get the Spektrum SPM4649T "quad-copter" receiver with telemetry and also use two DSMX sat receivers connected to the Brain 2.
The SPM4649T connects to the Brain 2 on the CH3 port using a single wire bidirectional SRXL (simple M-to-M servo cable).
Assuming you have a DX8 (or bigger), the SPM4649T has a telemetry down link to the transmitter and delivers similar telemetry as the Spektrum TM1000 does
This allows you to monitor engine temp, flight pack voltages and SPM4649T receiver frame loss, holds and fades.
Because the SPM4649T has single wire bidirectional SRXL, the Brain 2 sends its telemetry back to the transmitter in real time and expands all the channels coming from the transmitter (DX18 has all 18 channel or DX9 has all 9 channels)
All the servos connect to the Brain 2 as normal, so there is no messy wiring to deal with.
The SPM4649T is a single receiver that does not allow for additional satellite receivers to be connected.
It is billed as a "quad-copter" receiver and not for "big helicopters".
However, the BrainDev team has figured out how to have 2 additional DSMX sats connected to the Brain 2 ext receiver ports and use the signals from all three receivers (triple redundancy) and still use the SPM4649T's telemetry downlink.
With this setup, you are safe.
I use this setup on my Trex 600E and Goblin 380.
There are guys I know and have flown with this setup on their MSH Protos Max V2, SAB Goblin 700 and Align Trex 700E.
Personally, I use the AR8010T and the Brain 2 on my Trex 600N and 700N.
The AR8010T has the same telemetry as the TM1000, 1 internal RX and ports for up to 3 additional DSMX sats.
It also has an output-only, single wire, SRXL link to the Brain 2 (keeps the wiring clean).
Because the AR8010T is output-only, there is no real time downlink from the Brain 2 to my DX9.
But, I get head head temp, flight pack voltage, fades, holds and frame loss telemetry. And, it is "quad-redundant" with 4 receivers.
And, it decodes all 9 channels from my DX9 (instead of only 8).
I can use the Brain 2 to log any of the standard stuff, and then look at it after the flight.
Having any receiver that uses SRXL and telemetry allows you to put the receiver anyplace on the helicopter that has good "visibility" back to the transmitter for maximum telemetry connectivity / reliability.
And then having additional sats makes the TX / RX connection as reliable as it can be.
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