Could Spread Spectrum be just around the corner?

If it is constantly changing channels because there is interference on one channel, that means we could only have one plane in the sky at one time.

you would think that since this world we live in also shares the 2.4ghz frequencies with cordless phones and computer wireless networking (802.11b) that you could possibly get interference from that too.

Not quite Vance. I don't claim to be an expert but I see you don't understand the way it works. It doesn't change channels because of interference. It changes channels constantly, regardless of the situation. Many times a second. It's a form of encryption. It uses 25 channels essentially all at the same time. It shifts between these channels in a pattern determined by some algorithm built into the radio. So it doesn't hit each channel in numerical order but in some pattern known by the Tx and Rx.

Read the four levels of protection at the bottom of this page:

The Tx and Rx are in sync with each other. What this means is the Rx also knows the pattern and is expecting to "hear" from the Tx at the prescribed time on the prescribed channel. Correct channel at wrong time is ignored as is correct time on wrong channel. Even another R/C Tx using the same pattern would not cause interference unless it was in the same exact spot of the pattern at the same exact instant in time. And instant is the key here because to our perception it is only an instant that it is on any given channel. If fact, I suspect it hits each channel several times each second. And if I remember my math correctly, with 25 channels we end up with well over 13,000 possible patterns (probably more but hey, do we need more?:) which would equate to the possibility of 13,000 models in the air at once.

Likewise, any phones or wireless computers would have to be on the same set of channels and the same pattern to cause any problems. As would the Line of Site microwave shots and Satellite links that used this band. This is a proven technology that has been in use for years. It is simply, finally being implemented in R/C. About time too!

Chuck

Thats true! These chipsets have been around for a long time. The neat thing here that hasn't been talked about is the ability of the chipsets to be transmitters/receivers together, meaning each side can transmit and recieve at the same time. You standing on the ground sends signals to the plane, the plane can send signals back using the same frequencys. Instant data back about airspeed, engine rpm, gps, any thing you can think of to be displayed realtime on your transmitter! It's closer than you think!

Fred

So Red, what do 'ya think; will existing radios be able to be converted to spread spectrum or are all those high-dollar radios in use going to become obselete overnight when SS happens?

MJC

My guess is that the modules will be replaceable. Everyone with "standard" radios will be out of luck. I also suspect a rather long phase in-out period to allow the older sets to be either converted or used long enough that the sting of replacement won't be so bad.

That is always the issue with introducing new technology. IMHO - I do believe that when this issue comes to the forefront, that the FCC will be happy to help us! I think there is enough demand for our current frequency allotment by other interested parties that converting into the 900mhz or other currently used spread spectrum bands will look like a win/win solution to them. They have already allowed the Hams to experiment with spread spectrum data transmission on certain bands. All I can say is that it will get interesting!

Fred

| So Red, what do 'ya think; will existing radios be able to be converted to | spread spectrum or are all those high-dollar radios in use going to become | obselete overnight when SS happens?

As mentioned by another poster, radios with modules will probably be changable by just replacing the module.

As for other radios being obsolete, no. We can't just start using spread spectrum on 72 mhz -- if people do start switching to spread spectrum, they'll need to use another frequency range. So radios on

72 mhz will keep working and will be just as good as they are today ... as long as the spectrum isn't sold to the highest bidder. Spread spectrum does play reasonably nice with other types of radio emissions, but even the perception of causing problems would be bad.

I'm not sure if 900, 2400 or 5800 mhz is the answer, however. The power limits on these bands will severely limit the range usable by a spread-spectrum system. That, and these bands are full of junk. Spread spectrum does tend to ignore noise, even if the noise isn't spread spectrum itself, but the noise will reduce performance. Your plane won't crash (unless the whole band is saturated) but response speed could drop. Your microwave can easily kill your WiFi network, as can your 2.4 ghz cordless phone.

Ideally, another band would be allocated just for R/C, just for spread sprectrum. No need for an air/ground split. The power limits would be high enough to allow the same range we enjoy. Of course, spectrum is money, so I'm not holding my breath. :)

I suspect any current radios with Freq Modules will be easily converted. Those with built in RF decks may prove to be more trouble than they're worth. But this will probably be on a case by case basis as I'm sure some designs may lend themselves to easy conversion.

Chuck