Futaba site

[DavidH]

http://2.4gigahertz.com/

[ZX11]

Looks cool.

Not sure about that channel shifting technique. Almost sounds like Futaba thinks they are going to use all 80 available channels each time it gets turned on. It better check the channel for use before transmiting on it. Any transmitter that uses all the channels at once or in sequence is better known as a jammer. See Futaba join the 2.4 Ghz party but still have to wait for and check out the frequency pin (for 2.4Ghz) :rolling

[DavidH]

There is more than 80 frequencies available in the 2.4 ghz band.
Futaba is constantly rolling frequencies just like a lot of other devices that are radio controlled do.
The radio has been used. It was used at the E Fest last weekend with no problems.

David

[Danal Estes]

Looks cool.

Not sure about that channel shifting technique. Almost sounds like Futaba thinks they are going to use all 80 available channels each time it gets turned on. It better check the channel for use before transmiting on it. Any transmitter that uses all the channels at once or in sequence is better known as a jammer. See Futaba join the 2.4 Ghz party but still have to wait for and check out the frequency pin (for 2.4Ghz) :rolling

"Channel" is a very slippery term in Spread Spectrum parlance. SS devices see anyone not on their "chipping code" as noise, even if on the same "Channel". For example, setting up a building full of 802.11 Access Points? Their channels will overlap. No problems.

Much more compelling example: E Fest had several Fut and several Spektrum in the air at the same time. No issues.

[DarkWombat]

Well it's great to see that Futaba is coming out with 2.4 ghz products. I've heard rumors (which will be dispelled come the end of this month) that Spektrum will be making an announcement and will be releasing 2.4 ghz modules for JR and Futaba radios.

The problem with Futaba developing their own 2.4 ghz system is that this seems like a forshadowing that each radio manufacturer will have their own system and, like with PCM, each one will work differently and there will be no compatibility with each company's proprietary system. Something needs to be done SOON to make sure that this does not happen before we have ten different DSM systems that all work differently from each other.

[DebianDog]

Cooooome on 8 or 9 channel :D

[lennydude]

http://2.4gigahertz.com/

Wow................That looks great David :) And the street price for that entry level system is right on the mark..................!

We all knew it was just a matter of time B4 Futaba got into this market..............things are going to get interesting over the next year :):)

Lenny

[BarracudaHockey]

I have a feeling its going to be exactly like PCM with each manufacturer having thier own encoding scheme.

[ClayK]

I have a feeling its going to be exactly like PCM with each manufacturer having thier own encoding scheme.

Isn't that a good thing? If they all have their own encoding and they channel hop, I would think you get more out of the band than a fixed transmission with similar encoding.

[ZX11]

SS devices see anyone not on their "chipping code" as noise, even if on the same "Channel".

So I will still get my data packets while futaba noise is on the freq (channel, whatever)? I find it hard to believe that two unrelated transmitters can share the freq unless they cooperate and time share it. I have equipement that shares the freq by cooperating with each other (TDMA). However, interupting a router for a split sec and interupting my helicopter a foot off the floor for a split sec are two different things. We know futabas definition of speed is slower than Spektrums definition of speed :wink:

Much more compelling example: E Fest had several Fut and several Spektrum in the air at the same time. No issues.

Ahh, if it works it works. Just pissed that Futaba designed to hop to used channels instead of just staying on a couple of unused channels.

[MarkD]

Ahh, if it works it works. Just pissed that Futaba designed to hop to used channels instead of just staying on a couple of unused channels.

The rules etc. layed out for 2.4Ghz state that any Tx must not occupy a channel that is already in use. The Tx will see that a channel is being occupied and skip it and move onto the next one and so on. It doesn't use used channels

[Danal Estes]

The rules etc. layed out for 2.4Ghz state that any Tx must not occupy a channel that is already in use. The Tx will see that a channel is being occupied and skip it and move onto the next one and so on. It doesn't use used channels

With greatest respect to MarkD, while this statement is oft repeated (it is even on Spektrum's web site), it's not really true. One way to see that it's not even a meaningful statement: What is a "Channel" on 2.4Ghz ISM band? Spektrum thinks there are 80 of them... 802.11 networking standards define 14 of them... of which only 1-11 are usable in the USA... and THEY OVERLAP!! So, there is no true definition of "Channel" on 2.4.

[MarkD]

OK so the wording "Channel" is still used due to the FM system. The 2.4GHz is still fixed to a certain freq bandwidth so why not channels? - be it your microwave, cellphone, RC heli - all operate on set(be it changing) freq's

What I am trying to say here is that the Futaba, XPS, Spektrum systems cannot/should not lock onto a freq already used by another transmiter
In reply to ZX11 - Futaba won't use an already used freq(Channel) it will see that it's unavailable an move on

[ClayK]

SS devices see anyone not on their "chipping code" as noise, even if on the same "Channel".

So I will still get my data packets while futaba noise is on the freq (channel, whatever)? I find it hard to believe that two unrelated transmitters can share the freq unless they cooperate and time share it. I have equipement that shares the freq by cooperating with each other (TDMA). However, interupting a router for a split sec and interupting my helicopter a foot off the floor for a split sec are two different things. We know futabas definition of speed is slower than Spektrums definition of speed :wink:

Much more compelling example: E Fest had several Fut and several Spektrum in the air at the same time. No issues.

Ahh, if it works it works. Just pissed that Futaba designed to hop to used channels instead of just staying on a couple of unused channels.

First, if the "noise" doesn't affect other transmitters because of the coding, what does it matter? How can you find it hard to believe that two transmitters occupying the same band won't crosstalk? I would think that this has been proven with cell phones and the newer home wireless phones. Both share the same bands (not with each other, but within their respective class) and they have no crossover. I don't pick up other peoples cell phone conversations with my cellphone and I don't pick up houses using wireless phones anymore. Wonder why that is...?
Second, how is Futaba's definition of speed slower than Spektrums definition, example please. The 12z and 14mz are two of the fastest radios out there.
Third, there is a code transmitted with the packet of data. If the code is not the same code expected by the RX, it's ignores the rest as "noise". This would also be applicable to your second statement. It doesn't matter what traffic is on the channel, if it doesn't have the auth code for the TX/RX it ignores it. Why would you be "pissed that Futaba designed to hop"? Obviously the RF engineers that designed it seem to think that's it's applicability is more successful than a direct, constant link. If it works and you don't know the difference, what's to complain about? :dontknow

[ZX11]

What I am trying to say here is that the Futaba, XPS, Spektrum systems cannot/should not lock onto a freq already used by another transmiter
In reply to ZX11 - Futaba won't use an already used freq(Channel) it will see that it's unavailable an move on

That is cool then. Makes sense that FCC hasn't changed so much that they allow interference.

ClayK said,
How can you find it hard to believe that two transmitters occupying the same band won't crosstalk?

First, Band and Freq are two seperate things. I was talking about frequencies. UHF aircraft band has room for plenty of transmitters at the same time. But you won't see two transmitters on 225.000Mhz at the same time. You don't pick up other's phone conversations because you are either on a different frequency in the band or you have a different slice of time on that frequency.
Second, the 9C radio is Futaba's speed king in the sub $million dollar radio class :wink: But I am glad the 14mz can almost keep up with the spektrums. I kid...I kid. I guess a 14mz is great, if a little glitchy.
Third, if the futaba jumped on my channel and my receiver ignored it then while the futaba is on the freq my transmissions won't be heard. I know that looks like noise to the receiver, but it had better stop long enough to get a good data packet thru from my transmitter. Not an issue really since like Mark said, the FCC won't let you jump on a frequency in use.

As younguns, my friends and I used a signal generator with 10watts on 94 mhz to jam out a country radio station. It only affected our building. Sorta anyway. The listeners in the building could tell (without packet ID) that we weren't the country station, but they still couldn't hear the country music they wanted. We just gave them noise (1000hz tone). A goverment office tracked our antenna and told us what the penalties could be for hopping on that freq. They weren't even the FCC.

[ClayK]

It's no secret that the 9c is slow, it's the processing inside.

Cellphones use the same band and the same frequency. You don't pick up other conversations. Analog phones had issue with noise, digital do not. One of the reasons why we have dropped calls today on a digital network is because there is too much co-channel and adjacent channel traffic. When I say "too much", I mean a lot of traffic (hundreds). The point I'm trying to make is, co-channel habitation by the signal would require hundreds of independent signals to cause damage to any one of the single signals in that channel.

How is the 14mz glitchy? I've had it for almost a year and haven't had one problem with the radio. In fact, just about everyone I know either has a 12z or a 14mz and only one person had a problem. The one person with a problem, was a stick pot. In fact when I fly anyone elses radio, regardless of the manufacturer, their radio feels slow and I don't feel connected to the model.

Third, your transmissions would be heard. In order for your RX to ignore the transmissions, the channel would have to be saturated with noise. Saturated, not the occasional channel hop transmission that has it's on id tag sent in the packet. The whole purpose of Spread Spectrum technology (http://en.wikipedia.org/wiki/Spread_spectrum) is to ignore packets that don't have the appropriate id.
First, they occupy more than one channel at a time. Second, they use an encoding so only the RX and TX know where they are and where they will be along with encapsulating the traffic for only one recipient.

Your example simple displays a noise generator. You saturated the RF environment, albeit only for a short range, on a single channel, single transmission platform. Radio does not use spread spectrum technology, so comparing each is like comparing polar bears and bunnies. They might both be animals but they are different in every other way.

[Danal Estes]

OK so the wording "Channel" is still used due to the FM system. The 2.4GHz is still fixed to a certain freq bandwidth so why not channels? - be it your microwave, cellphone, RC heli - all operate on set(be it changing) freq's

What I am trying to say here is that the Futaba, XPS, Spektrum systems cannot/should not lock onto a freq already used by another transmiter
In reply to ZX11 - Futaba won't use an already used freq(Channel) it will see that it's unavailable an move on

Completely agree that they listen before they transmit and pick the cleanest spot. This is a great feature/implementation.

But...

The original statement was "The rules etc. layed out for 2.4Ghz state that any Tx must not occupy a channel that is already in use." The "rules" do not state this. They can't as there is no "rule" definition of "channel". Further, while Spectrum and Futaba do 'listen before transmit' (XPS - We'll see if they ever ship), 802.11 APs do not. 802.11 APs are fully rule compliant, they are pre-configed for "channel", and each of their "channels" occupies the same bandwidth as several of, say, Spektrum's "channels".

Again respectfully, if you believe the rules state this, can you provide a link to the FCC site where this appears?



Summary: Agree that Spectrum/Futaba listen before transmit and attempt to pick the clearest spot (channel). Disagree that there is any FCC rule that mandates this.

[ZX11]

Cellphones use the same band and the same frequency. You don't pick up other conversations.

Cell phones are a network. They share the frequency by taking turns on it. No big thing, we know it works.

How is the 14mz glitchy? I've had it for almost a year and haven't had one problem with the radio.

I kid. Easy to poke fun at the Rolls Royce <sp> of radios. Originaly I was just talking about Futaba being known by their 9C.

The whole purpose of Spread Spectrum technology is to ignore packets that don't have the appropriate id.

Here is where we disagree. I was pissed at the notion that Futaba would purposely put any noise at all on the signal between me and my model. They really just want to hop around it and that is fine.

Radio does not use spread spectrum technology, so comparing each is like comparing polar bears and bunnies. They might both be animals but they are different in every other way.

Spektrum's spread spectrum technology uses only two channels. You purposely put noise on one of those channels with a signal generator or a radio when there are 78 other channels you can use, I will be pissed. Thats just the way I am :bomb:

[DavidH]

You know the key thing to all these radios is that they work. It really makes no difference how they get them to work. Just long as they control the model safely is all that matters.
I have been doing this hobby for nearly 20 years now. As long as the radio controls the model as I expect it to. That is all that matters to most people.


David

[ClayK]

Thanks David, that was more or less of my point. :glasses2:

[SteveL]

If you are going to be pissed at anybody be pissed at Spectrum for leaving you vounerable to this.
Frequency hopping is what allows many people to use the same band at the same time.
If you think you could notice a 2millisecond hit (for lack of a better word) then you are a lot better pilot than me.
I have run comercial 900mhz systems right next to each other for years and one brand is frequency hopping and the other is not. I have never had a problem with latency or dropped packets. (Except when someone built a building in the way.)

[kgfly]

zx11,

I think you have not grasped the significant technological differences between the old FM (PPM/PCM) radios and spread spectrum radios. The nature of spread spectrum is to spread the signal across many frequencies. Amongst the many benefits is the 100 to 1000 time greater sensitivity that results from the spreading gain. Time-division or Frequency-division multiplexing are certainly not the only ways to share spectrum, have you not heard of CDMA cell phones ? The "CDMA" stands for "Code Division Multiple Access". This is spread spectrum technology at work with multiple simultaneous transmissions not only in the same band but on the same carrier frequencies within the band, and that's perfectly OK for spread spectrum radios.

As mentioned above, all energy in the band that is NOT encoded with the approriate spreading code appears as noise. If there is enough background noise then sure a packet can get lost. For the R/C systems under discussion it would take a very large number of simultaneous FHSS Tx to have any noticable impact on each other or on DSSS Tx. While you may not like the idea of multiple Tx using the same frequency and even though this will cause a small marginal decrease in S/N ratio, it is not a reliability or performance problem.

Spektrum chose to divide the ISM band into 79 logical channels. Nomadio/Futaba FHSS may use the same number, more (unlikely) or fewer. XPS/XL uses DSSS on a single channel but has the ability for either the Tx or Rx to initiate a jump to another channel if either detects too much packet loss on the current one. All of these systems will (most likely) coexist happily (Spektrum/Nomadio/Futaba already do with the car radio systems and Spektrum/Futaba recently have with their air systems).

Then there is also the fact that unlike FM, all these new radios use low-duty cycle transmission so your preference for non-simutaneous use of frequencies will be achieved most of the time, giving additional security over and above that inherent to the spread spectrum approach.

[kgfly]

Frequency hopping is what allows many people to use the same band at the same time.
Frequency hopping is one way of sharing the band but is neither necessary nor sufficient on it's own to ensure reliable operation. FHSS and DSSS both have strengths and weaknesses and both can and do work and can and do coexist.

[DarkWombat]

I'm probably wrong here but if you're constantly frequency hopping wouldn't there be a greater risk of packet loss and/or higher latency? I think it makes more sense to frequency hop ONLY if the current channel becomes saturated with noise.

In any case the digital GUID codes that the TX/RX recognize should block most interference right there, right? Broadcasting on multiple channels is just another form of redundancy, which is why I think Spektrum's setup that uses two channels simultaneously should work fine. I'm sure Futaba's will be fine too it's just that there could be greater latency between the TX and RX.

I'm not well versed in wireless communications so correct me/enlighten me if I'm wrong.

[SteveL]

If the hop pattern is set up like the comecial radios I use then no. The hop patern is dertimeined on bootup and set by the master. Once the 2 radios are synced, they both know where they are going next. They don't look or care what is on the frequency they are going to they just go.