Thread: Rave Futaba T8J S-FHSS
View Single Post
Old Oct 16, 2011, 03:00 PM
renatoa is offline
Find More Posts by renatoa
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
17,595 Posts
Any current 2.4GHz RC system contains two parts:
- a RF stage, which actually is a radio modem, at both ends it behaves as a serial line, nothing else.
- a microprocessor which, at Tx side transform the PPM pulses into numbers and send them over the aerial serial line to the receiver, and at receiver side gets the numbers and synthesize the servo control pulses accordingly.

Everything that is related to range, link quality, diversity is controlled by first chip. In both FASST and Frsky it is the same ML2724DH, in S-FHSS I don't know. This chip is a general usage transceiver, from 2003, go figure how much innovation brings the big brands... Also, for those not familiar with RF glossary, transceiver comes from transmitter-receiver, a combo device, so, at least in theory Futaba should be able to turn its system into a bidirectional one, only by a firmware update, as Frsky does.

The microcontroller contains the FH and binding logic, so if a Frsky receiver is now able to bind to a Futaba Tx, we must suppose that the Futaba labeled IC is also a similar MCU as Frsky, or at least run a program with an identical behavior. I wouldn't advance the cloning hypothesis, I know that was rather a reverse engineering. Anyway, the program ran by this processor does not influence the link robustness, Futaba has no merit here. What they own as IP in all this stuff is the FH algorithm, but seems it is not something magic, all FH systems today seems to prove at least same robustness as Futaba.

If someone can open a S-FHSS receiver and make photos of its chips, maybe we can elaborate more about what could be so special in S-FHSS.
My guess is: nothing ! Why I say this... the time required to send 16 channels data with current technology is about 3-4ms. So, the 20 and more ms latencies of FASST and other PPM systems are only imposed by the backward compatibility with PPM and FM transmitters. When you start building systems that has no heritage to preserve, and remove this old framing, 7-8ms response times of S-FHSS should be the norm for any mfr, and nothing special. And this is the only argument from S-FHSS ads.
renatoa is offline Find More Posts by renatoa
Reply With Quote