questions about 2.4mhz (spektrum,futaba,etc)

[tobytorkn]

hey guys, i'm about ready to plunge into the 2.4 arena but have some serious questions about the technology. after spending about 2 lifetimes reading and re-reading info about spread spectrum and talking to a few modelers i have a few questions.

#1. i see that futaba basically transmitts on one frequency but uses "frequency hopping technology" where the frequency is being change every few seconds. to me this seems to make sense incase another user (lets say a cell phone) comes through your area on the same frequency. i know the spektrum system uses at least 2 receivers on different channels. does the spektrum system do "frequency hopping" as well? if not; then, what do you do to prevent interference on an intruding device on the same frequency?

#2. Per the spektrum website it says that the receivers can operate on the available 79 channels. you will have to bind the tx to the rx to obtain the clear channels. now, lets say at a large event you have 20 people turning off and on radios, binding them, using their cell phones, etc how does futaba and jr (spektrum) compensate for all of the noise. does the guid coding compensate for multiple users on the same channel or what? does futuba use guid coding like jr (spektrum)? it seems to me like the big players in this technology are solving problems by different methods.

i guess the reason for the questions and worry is because the hospital i work for installed a 2.4 internal phone system (about 500 phones by my estimate) and on a good day the phones are staticy when you use them. the system was put in place to get rid of people wearing 2-3-4 beepers at a time (now i just wear 2 beepers and 1 phone now).

to anyone answering this, i would love to have the definitive answer-not speculation. i have read litterally a thousand posts on this and there is so much non-sense garble with people talking out their butts i would just like to have a straight answer.lol. i know a lot of people i've talked to at the field have these same questions and some professional advisement would really help the masses. thanks to anyone answering these questions!!!! toby silhavy....
www.silhavyaerosports.net

[BoneDoc]

As per 2.4 Ghz regs, the Tx will scan for available channels. No available channel = no transmission.

Spektrum changes channel if one of them gets interference / problem. In theory, the redundancy helps prevent interference.

[Stu_D]

I will give this a go , as explained to me by two seperate radio techs

1 . futata ferq hopping yes , every milli seconds
. Spektrum freq hopping no .

2 . Noise is no so much of an issue as there are so many combinations in 2.4
. Futaba system does appear to be a better way of doing things
. Binding and using the tx to rx for controll are not the same thing , bindind
is done once during initial setup and not again . Call it macthing of the Rx and Tx .

3 . Your hospital system is something to worry about .
If a 2.4GHz high strength (say 50 watt)directional signal is between Tx and Rx
you will be cut off . (This is a problem we have with our 72 systems as well)
Solid objects will also cut you off .(moot point ) .

This is the info I was able to come up with .

Stu

Forgot one thing ,the real question is how will Futaba and the other systems behave
when side by side .

[tobytorkn]

bonedoc, thanks for the reply. so are you saying that the tx/rx (jr/spektrum) will change channel during flight if one of the channels becomes "dirty" or that it scans when initialized (radio start up) until it finds a "clean" channel? thanks, toby silhavy....
www.silhavyaerosports.net

[BoneDoc]

Yes, that's my understanding of it. It just doesn't do it unless that happens, unlike Futaba's FASST.