How spread spectrum RC systems can share the same part of the 2.4GHz band

This is a very quick explanatory video which hopefully explains how a DSSS signal (as used by all of today's 2.4GHz radio control systems such as Spektrum DSM2 and DSMX, Futaba Fast, Hitec AFHSS etc) allows more multiple systems to share exactly the same part of the band without interfering with each other.

The PN (pseudo-noise) codes effectively "scatter" the signal across the channel being used by the DSSS signal so that the chances of another signal affecting it are very remote.

This could be seen as a kind of "micro-hopping" within the DSSS signal itself -- although it shouldn't be confused with the much larger jumps that today's "hopping" systems use to move the entire DSSS signal around the band at random.

If you have any questions, please feel free to ask and I'll do my best to explain.

Category:

Science & Technology

Tags:

• radio
• control
• model
• airplane
• 2.4GHz
• Spektrum
• Futaba
• JR
• Hitec
• FrSky
• PN
• codes
• spread
• spectrum

[wallaguest1]

and whats the difference between FHSS and DSSS? looks the same to me

[RCModelReviews]

@wallaguest1 "true" FHSS uses a very narrow signal like our old 72MHz signals which hops around all over the band. Interference can totally wipe-out the very narrow signal in parts of the band. DSSS uses the much wider (inverted funnel shaped) signal which is spread out much wider so is harder to interfere with. Today's RC systems don't use true FHSS -- they use a DSSS signal that hops around the band so you get the benefits of FHSS *and* the benefits of DSSS.

[simscody3]

Hi rather starting new videos how about finishing the ones you said you were going to like the 9x frsky mode, after all that why i donated

[RCModelReviews]

@simscody3 That video is being edited as I type this. The DIY vids are a *lot* harder to make and edit than a simple presentation like this (which took about 15 minutes). Quite often with a DIY vid I have to go back and re-shoot some shots because they're not clear/obvious enough when you look at the footage later in editing. Doing it properly sometimes that takes a little longer.

[gruntboy50]

i just want to say. I have learned more in your 10min youtube video than in an entire semester of communication theory. That was incredibly educational.

[SaToMojo]

Thank You Professor Bruce ;)

[SphinctersForever]

@xjet Thanks! I'm glad to hear that. Not that I wouldn't probably upgrade in time (the newer systems seem to have much smaller flight-side components than the older ones did), but it's good to know that I can get back in using my old equipment, much of which was top-of-the-line (and expensive!) way back when I last flew.

[xjet]

@SphinctersForever (I'm posting from my other YT account but it's me) -- yes, of course you can still fly your old gear. In fact, there's never been a better time to fly 72MHz because the band is almost deserted because so many other people have shifted up to 2.4GHz.

[SphinctersForever]

So here is a question: I haven't flown anything in probably 15 years, and I have a very nice Futaba 7UAP "PCM 1024" system in the old 72 MHz band, I think it's channel 14. I used to have a Great Planes Super Kaos 60 that I flew the heck out of with it and it was a great radio. If I go flying somewhere (where no one else is around) am I likely to get hammered by modern radios? Can I still fly with it at an organized field using the frequency queue board as we always did before?

[jonathanglass]

This is a brilliant video giving a clear explanation of a tricky concept. 10 out of 10 for the instructional technique. To simplify this in such a way, with a small amount of artists licence, shows just how valuable Bruce's input is to our hobby. Well worth another donation from me!!

[hot4plasma]

Excellent video! What more can I say than really great explanation. Please stick to this medium of communication, because you are very good at this! Have faith that you'll make money enough to keep your talents on the web.. thanks for making this, it really helped me understand.

[lesdeuxciel]

Gray code (aka state diagram for binary code) was used in the earliest days of semiconductor designs due to possible errors from single transistors failing to stabilize across a bank of them arranged as a memory register. Gray code enforced change of only One bit at each clock pulse: 0000 0001 0011 0010 0110 0111 0101 0100 1100 1101 1111 1110 1010 1011 1001 1000 0000 Motorola may hold a patent on its use for microcode in microprocessors. Nixdorf may have something, too...