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Originally Posted by Nesti
Funny enough, radio controlled planes and helicopters were the first to benefit from this signal (Called Spektrum), which allows up to 10 radios to be transmitting concurrently without any interference. It doesn’t work with carbon fibre between origin and receiver, the shadow corrupts the link.
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Just to clarify a couple of things, Spread Spectrum has been in use for some time, for example the old CDMA mobile phones used a variant of it, wireless networking(WiFi) uses it.
I consider the RC world pretty slow on the uptake... infact, I got sick of waiting so started designing my own 2.4GHz transmitter modules(to suit Futaba Tx's) when Spektrum(brand) in collaberation with JR released their stuff... I gave up on mine, cheaper and quicker to buy someone elses!
Spektrum is not really spread spectrum, once binding has been done, they are tied to that channel... atleast that was the case in the beginning.... not so sure about the newer Spektrum radios.
Futaba and Hitec do use Spread Spectrum (FASST and AFHSS respectively)
The 2.4GHz ISM band (Industrial, Scientific, Medical) has 13 channels available, with TDM (Time Domain Multiplexing) there can be hundreds of 'pseudo-channels', I recall reading about some huge meeting in the US years ago where the organisers decided to crash test the emerging 2.4Ghz systems by asking all that attended to turn their transmitter on at the same time(all aircraft grounded)... don't remember the exact figure but there was something like 100 transmitters and receivers all on at the same time and not a single case of interference was reported.
While designing my system, I decided that interference(as in erratic behavior) was impossible.
Loss of signal could happen(would be
almost impossible), forcing receivers into failsafe mode, but interference as modelers think of it(someone else controling their model) is just not possible. I'd explain why, but it would blow this post out to 10,000+ words.. haha.
The MAAA in its infinite wisdom set the 10 transmitter limit.
Anyway, enough of that from me
I believe the wireless black box system possible, it will take lots of money and time, but it can be done, the technology is there, there are large swathes of the radio spectrum that are not being used so the bandwidth is there.
Just have to get the ball rolling, most airlines around the world initially resisted the introduction of the black box. It was only after it became mandatory that anything happened at all.