Monday, 19 February 2007

Is Spread Spectrum good for you?

The success of the Spektrum DX-7 has taken 2.4 GHz firmly into the mainstream of R/C modelling. Yet while 2.4 GHz systems offer enticing advantages, there are some subtle compatibility issues to trap the unwary purchaser.

As you might expect, the two major systems (DSM and FASST) are not compatible, i.e. you can't operate a DSM receiver with a FASST transmitter and vice versa.

In addition however, there are compatibility issues within brands; for example, the DSM-1 Spektrum DX-6 does not support the latest DSM-2 AR6100 parkfly receivers. And Spektrum are not alone - Futaba's R606FS FASST receivers will only work with dedicated FASST transmitters. They will not work with FASST RF modules, as shown in this compatibility table.

Apart from being confusing for anyone contemplating a purchase, it begs the question: will the 2.4 GHz receiver you purchase today work with the transmitter you buy tomorrow? So here are some questions you may like to ask if you're thinking of dipping a toe in 2.4 GHz waters:
  • How long will the manufacturer support the protocol supplied with your system?
  • Is the protocol shared with other brands? (safety in numbers)
  • Is the firmware on your transmitter and/or receiver(s) upgradable to work with future protocols?
Contrast this with PPM systems, where any brand of transmitter made in the last 20 years will work with almost any brand of receiver made during the same period. Somehow, good old PPM is beginning to look rather appealing!

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