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Can Futaba FASST and Spektrum systems peacefully coexist?

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Old 02-23-2007, 04:46 PM
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JustABigKid
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Default Can Futaba FASST and Spektrum systems peacefully coexist?

I've read statements by Horizon reps that there isn't a problem with Futaba FASST and Spektrum DSM2 systems sharing the 2.4 GHz channels. But I'm not so sure... [sm=confused.gif] The Futaba system constantly hops around the 2.4 GHz channels, changing every 2 ms. The Spektrum DSM2 system needs to find two UNUSED channels during the bind process. This may not be a problem with just two radios in use, but at a busy flying field with several people flying, plus a dozen people working on their planes in the pits with the radio on, a mix of FASST and DSM2 system could be a problem...

And, if you've got a bunch of FASST systems hoping around the channels randomly, and a bunch of DSM2 system holding onto two channels each, couldn't there be situations where two FASST systems step on the two channels of a DSM2 system? It seems to me that in a few years we could be experiencing constant minor glitching when flying.

I think this could be a case where it would be better for the AMA to require a single standard protocol (like DSM2) rather than allowing two different protocols which randomly glitch each other...
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Old 02-23-2007, 04:52 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

It was proven at the E-Fest and is required by the FCC. There is not one shred of actual proven data that indicates that they do not work together just fine. So why do we have to keep beating this dead horse???

As far as the AMA goes, they do not require anything beyond following the FCC regulations. And again, the FCC certification standards REQUIRE that the 2.4 systems work without conflict to other systems.

But let's keep speculating away.
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Old 02-23-2007, 04:59 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

ORIGINAL: Phaedrus-MMVI

It was proven at the E-Fest and is required by the FCC. There is not one shred of actual proven data that indicates that they do not work together just fine. So why do we have to keep beating this dead horse???

As far as the AMA goes, they do not require anything beyond following the FCC regulations. And again, the FCC certification standards REQUIRE that the 2.4 systems work without conflict to other systems.

But let's keep speculating away.
I'm interested in how this question could be "proven" - algorithmically proven? proven by monte carlo simulation? If a couple of guys fly planes using FASST and DSM2, that doesn't actually prove anything...

I'm worried about the situation in a couple of years, when most people have bought these new SS systems, and we have 50 flyers at my field here in LA all switching on their radios whenever they feel like it...
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Old 02-23-2007, 05:05 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

Does the Futaba system use all the channels on the band, or does it only hop on a subset of the channels? It might select a subset of good channels and then hop on only those channels. This is how most other wireless communications systems work that use frequency hopping. They typically don't use all the available channels.

-Ed
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Old 02-23-2007, 05:13 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

I took a look at the Futaba Website and they don't use all the channels on the band and they use any of the many patterns of non-overlapping channels, so there shouldn't be a problem.

-Ed
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Old 02-23-2007, 05:38 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

I found the following statement from Futaba:
Futaba has done extensive testing in collaboration with not only the FCC, but with other manufacturers to make sure there that there is no conflict between these two different types of systems. This testing has been not only extensive but has encompassed many months, and everyone involved has complete confidence in our system.
But I couldn't find any technical test data on the Futaba site to back up this statement. The information I have been able to find on this 2.4 GHz technology leads me to believe that it is designed to be constantly dropping data frames, gracefully, without the user being aware of it. Dropped frames increase latency and cause momentary glitches. My question is: do the number of dropped frames increase with the number of FASST transmitters in an area? If so, then that could be a problem for busy flying fields...

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Old 02-23-2007, 05:56 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

This is all spekulation. They (Futaba and Spektrum) MUST follow FCC regs which specify that you kan't emit on an okupied 2.4GHz channel...Done.

If the Futaba system does, then they loose once the FCC finds out and shuts them all down. I'm sure Futaba's not going to let that happen as they are obviously very reputable (despite making krappy radios - kidding). I basikally just trust that they've figured it all out. Sounds like you're going to be skeptikal no matter what's said here so I say just wait.
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Old 02-23-2007, 06:15 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

To me this is just yelling "the sky is falling" If they say it will work it will. I wonder if we had the same questions when everybody stoped using reeds. Dennis
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Old 02-23-2007, 06:20 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

ORIGINAL: pappy35
This is all spekulation. They (Futaba and Spektrum) MUST follow FCC regs which specify that you kan't emit on an okupied 2.4GHz channel...Done.
Is that true? The FCC regs specify that you can't transmit on an occupied 2.4GHz channel? Because I found an article on RF Design website discussing the 2.4 GHz spread-spectrum devices which says:
(FCC) Part 15 regulates the operation of unlicensed devices. These devices must operate with minimal or harmless interference, while they must also accept any interference that they may receive.
This is leading me to believe that some level of interference is expected between 2.4GHz devices. This spread spectrum technology is very different from what we're used to on our own dedicated 72MHz channels...


Sorry if I've offended anyone by asking these questions. I work in the technology industry, and my experience is that sometimes complex technical issues get reduced by marketing people to "it works great!" I hope that in a few years time we all still think that 2.4GHz was a great thing to happen to RC.
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Old 02-23-2007, 07:21 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

Is that true? The FCC regs specify that you can't transmit on an occupied 2.4GHz channel?
Not from what I have seen it isnt. I have the entire Part 15 doc from the FCC downloaded and have gone over it and have not seen anything that says this. It actually states to the opposite in regard to frequency hopping systems. The very nature of the 2.4 band with SS is for devices to co-exist on the same bandwidth. I used to think the same thing since that gets tossed around so much, marketing hype would be my guess. Here is a link to a good primer on SS, it doesnt go in great depth but provides enough info to give someone at least a basic understanding.

http://www.maxim-ic.com/appnotes.cfm...te_number/1890

And the FCC part 15 docs http://www.fcc.gov/Bureaus/Engineeri...98/47cfr15.pdf
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Old 02-23-2007, 11:42 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

The reason you must accept interference is so that the Feds (read Department of Defense) don't have to worry about independent designers or companies (or terrorists) desiging and marketing (or utilizing) devices that can't be jammed. Every electronic device of any kind I've ever owned has had that "must accept interference" statement written on it.
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Old 02-26-2007, 11:32 AM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?


ORIGINAL: pappy35

The reason you must accept interference is so that the Feds (read Department of Defense) don't have to worry about independent designers or companies (or terrorists) desiging and marketing (or utilizing) devices that can't be jammed. Every electronic device of any kind I've ever owned has had that "must accept interference" statement written on it.
Sorry, but the regs state that you must accept interference in the sense that you have to live with it. You can't complain to the FCC about getting interference. You're not allowed to interfere with other systems, but if you get interference, you just have to grin and bear it. If you can build a system that rejects all types of signals but those you want, great! It has nothing to do with DoD requirements or something re: Homeland Security.

72 MHz is the same way. The channels are between those of high-power commercial users. We are not allowed to cause any interference with their operations, but we must accept any interference on our channels. That's because 72 MHz R/C operations are secondary to the other ones. If we get 'hit' by a high-power commercial user, we have no recourse...we must "accept" the interference...grin and bear it, in other words. Again, it's not because "un-hittable" systems may not be designed.

We've had a lot of experience over the years working with the FCC in transmitter certification, and that's what it means when the regs say you must "accept" interference.

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Old 02-26-2007, 12:09 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

Bax is right about part 15 devices having to live with the interference.
A legitimate ham transmitter can raise total havoc with a neighbors VCR or TV but it remains the responsibility of that VCR or TV to accept the interference. It is not an easy concept for me to explain to my neighbors.

Another point worth considering is the bandwith available at 2.4GHz is 80 MHz or 80 times the spectrum available between 72.01 MHz and 72.99 where we currently can share 50 concurrent users.

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Old 02-26-2007, 01:03 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

No! No!!! It's agovernment conspiracy damnit!!! [:@]

Kidding of course. Someone told me that a long time ago and it seemd to make sense in the light of that conversation. Of course, that guy was a radical right-wing-pistol-pounding-NRA-survivalist-maniac.

Thank's for the update.
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Old 02-26-2007, 06:53 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

Here's a timely piece of news:

http://www.cnn.com/2007/US/02/26/sig....ap/index.html

Notice the last paragraph:

"Consumer wireless devices, such as garage door openers, operate on an unlicensed basis, meaning they are required to accept any interference from licensed spectrum users, including the Department of Defense," said Lt. Brian P. Donnelly, a spokesman for the Quantico base.
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Old 02-26-2007, 08:46 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

That isnt timely news, it was reported when it happened in Co. a few months ago. And the bit about accepting interference is true of most all devices according to FCC regs, not just unlicensed ones.
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Old 02-26-2007, 10:02 PM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

It make pefectly good sense, for all these companies to spend a bunch of money on some crap that will never work as intended. (lots of sarcasm here)
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Old 02-27-2007, 01:24 AM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

Every one keep reading, time will tell. I will wait a while and see what happens.
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Old 02-27-2007, 02:12 AM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

ORIGINAL: chrisF test pilot

That isnt timely news, it was reported when it happened in Co. a few months ago. And the bit about accepting interference is true of most all devices according to FCC regs, not just unlicensed ones.
Please read the link. It references a recent situation in Virginia. It also makes note of the previous situation in Colorado. So it is in fact recent, especially since it was only published today.

Point is that we are secondary users. Now this is also still down in the megahertz band, but even on 2.4 we are not primary.
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Old 02-27-2007, 07:24 AM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

You are correct, I meant not timely in that it did happen several months ago also. We will always be secondary users regardless of what frequency we are on. I would gladly take secondary on 2.4 using SS than secondary on 72Mhz narrowband. Given the implementations going on at military bases across the country you will hear more and more about this happening. Major difference I think is consumer education, most people in RC are aware of frequencies we use and that we are secondary users. The reason that story is upsetting to people is because they dont know. I will have to try and find out but to my knowledge the military doesnt use the 2.4Ghz band either so we are much less likely to have something like that happen.
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Old 02-27-2007, 09:27 AM
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Default RE: Can Futaba FASST and Spektrum systems peacefully coexist?

Any communications systems that share the same frequencies or wires should deal with Collision Detection (CD) and Collision Prevention (CP). Collision is when two or more transmitters are on the same frequency or wires at the same time, corrupting the information.

As the quantity of transmitters increases, the quantity of collisions increases at a rate that is not linear.

The process of CP is very different for a transmitter that changes frequencies or wires than for one that stays put.

Without knowing if these systems do CD/CP and how they do it, it is not possible to estimate how they will co-exist.

Based on my experience with shared band communications, I assume two things:

[ol][*]They will never co-exist as well as the marketing department says they will. [*]If you have twenty transmitters of multiple brands operating, they will operate less efficiently than if you have two.
[/ol]
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