WRK

My Feedback: (2)

What happens if while using a JR Spectrum system the primary channel gets busy and then the secondary channel gets busy too, does it then hunt for two new open channels? Trying to figure out how this radio handles channel selection since it does not continuously switch channels like the FASST system.

WRK

DadsToysBG

My Feedback: (35)

The receiver itself will not see anything that doesn't have the GID with it. The GID is established when you bind the receiver to the radio. When you turn in the transmitter it scans for two open "channels" and the the receiver locks into those channels and the GID signal and will not see anything else. Dennis

Rafael23cc

My Feedback: (6)

The way the system is designed, and the restrictions placed on it by the FCC the probability of the two channels in use by a JR Spektrum system being utilized by another device should be minimal to non-existent.

The only way I see this as a possible problem is if you were to fly "cross country" to a neighboring field and at that field somebody already has your exact same two channel s already in use. But again the probablility of that is minimal. All of this even before we get into the GID.

There were over 700 pilots at the Biggest RC event in the World, IRCHA '07. Out of those pilots around 500 of them had spektrum systems. They were allowed to keep their transmitters and not have them impounded like the 72 MHz guys. Not a single problem reported over 4 days.

Rafael

BarracudaHockey

My Feedback: (11)

Remember that any compliant system scans the band before it transmits and won't use a frequency already in use. In the case of a FAAST system it would hop in and out so fast you'd never know and since the information it might output in that small time frame isn't tagged with the guid of your system, the reciever would ignore it in any case.

Four Stroker

There is no requirement to scan the band or to not use a frequency already occupied. This is PBBS.

For example: https://gullfoss2.fcc.gov/prod/oet/f...ive_or_pdf=pdf

See the summary page 7. That's all of the requirements. This is the 200 mW EIRP USA Spektrum TX module.

DadsToysBG

My Feedback: (35)

WRK, to keep it simple, thats the only way I can understand it. Is that the radio doesn't have to hop. It will stay on two channels until you turn off the radio. With the GID between the radio and receiver nothing else can get in. Dennis

chrisF test pilot

Straight answer to your qustion is if both channels get swamped with noise you lose control and crash. However, another 2.4 device occupying the same frequency doesnt necessarily equatee to noise. Multiple systems can and will operate on the same frequency. Just not multiple Spectrum systems. And as Four Stroker pointed out, there is no scanning and avoidance requirement, the specs and regs were designed such that with the nature of spread spectrum multiple systems can operate using the same frequency.

Four Stroker

You guys should search the net for a white paper explaining CDMA. In short, everyone is on the same frequency.

Rafael23cc

My Feedback: (6)

I don't have the time right now to read up on your link, but I will.

As designed, the Spektrum systems (JR/Spektrum) WILL SCAN for two empty channels and then transmit on those two channels. If two empty channels are not found the system will not work. At least that is what it says on their website and all the literature I've seen. I'm no radio expert, neither own a spektrum system right now, but I will in the near future.
From : [link]http://www.spektrumrc.com/DSM/Technology.aspx#howWorks[/link]
As BH said, on the other hand, Futaba systems hop around frequencies so fast that if it happen to stop at a used frequency, it will continue on and neither pilot will notice any difference.

Rafael

Mac_Man_UK

4stroke, I believe that Spektrum took the advice from various authorities before designing the system. As of now, in Europe the regulations state that a " Media Access Protocol" has to be implemented to ensure efficient sharing of the band. If Spektrum didnt listen first then it would never have gained approval in Europe (sorry I tell a lie... it would have been fine until July 08, but then it would have needed to be redesigned & retested in order for it to meet the regs.)

BalsaBob

My Feedback: (24)

I'm curious .... how many channels are there .... from which two are selected ? Thanks. Bob

bruce88123

Not to be picky but it's called a GUID. Global Universal ID Code.

BarracudaHockey

My Feedback: (11)

Spectrum radios use 80 discreet channels.

Over 600 systems in use at IRCHA with 720 some pilots, 18 flight stations and no impound and Futaba, Xtremelink, and Spectrum all got along just fine. If you go to a busier fly in than that you might have to wait 15 minutes to fly.

BalsaBob

My Feedback: (24)

Thanks Baraccuda. I can't imagine any airplane event (actually any event .....) ever having nearly as many pilots and radios as IRCHA. I can't think of a better test ..... than 18 flight stations. Bob