pchristy
Senior Heliman
Location: Nr London, England
| Both systems have their pros and cons. Its a very complex system, and not many people understand how it works. My profession is electronics, and I must confess that there are aspects of it that I find puzzling!
Futaba fans will tell you that because of the frequency hopping, the signal never spends enough time on any given channel to suffer interference, whereas because Spektrum only uses two channels, the chances of being "splatted" are greater.
What they neglect to point out is that a Futaba channel is only 100KHz or so wide, whereas the Spektrum one is 1MHz wide! Wider bandwidth = better immunity (in crude terms!).
Also Spektrum have been very careful in their choice of spreading code, which again gives a significant improvement in the ability of the signal to cope with noise. In fact the Spektrum system is capable of recovering a signal that is BELOW the noise floor - something that I and many others have difficulty getting our heads round - but the maths speaks for itself!
The most important feature of a spread spectrum system is the "path budget" - in crude terms, the dynamic range of the system.
Most conventional PPM and PCM systems probably have a path budget in the region of 70 dB or so (every 3 db represents a doubling of the signal, so 70 dB corresponds to a figure of around 10 million times!).
In contrast, the "path budget" for a Spektrum system is of the order of 130dB! This represents a substantial improvement!
I appreciate your position with an expensive camera helicopter, but consider this: NO model technology is going to achieve the reliability of full size. If it did, it would cost the same as full size! You are trying to use a "domestic" appliance for an "industrial" application. Really, you have no choice, because nobody (except the military!) makes "industrial" strength RC systems!
However, for my money, I am backing the Spektrum system. I was skeptical at first because I have designed and built my own RC systems on 459 MHz (legal here in the UK) and I know how much trouble I had getting those to work in helicopters! I couldn't believe that 2.4 GHz would not suffer from even worse issues! However, I was applying "analogue" thinking - Spektrum are applying "digital" thinking, and the evidence speaks for itself - it works!
Furthermore, the design team seem remarkably accessible if you have problems or special requirements - something that a large industrial outfit like Futaba would have difficulty providing. I have also become convinced that the Spektrum system is technically superior. And I'm putting my money where my mouth is by slowly switching all my important machines to Spektrum 2.4 GHz!
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Pete |
