garrett_mcdonal

Hi Guys,

I'm on the committee for my local club and we are looking at the operational side of allowing 2.4g radios. The national body has given the basic green light for use but has allowed individual clubs to make the call on whether they can be used and, if so, what operational procedures are applied.

They are here, no doubt about it, but there seems to be some discussion amongst the technical wizards at a national level about what happens when a number of 2.4g radios are operating at the same time. The below was sent to me by our club secretary who used to work in the comms field and has been tracking the debate.

Anyone else aware of discussion around these issues in the US or Europe? How did they go at Florida Jets?

Regards,
Garrett


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It would be extremely interesting to hear how they got on at Florida Jets.
The "degredation" slows down responses, rather than reducing range.
The degradation happens as the receiver finds itself working in what is effectively, a noisier signal environment - there are more "unwanted" signals around and so the receiver has to work harder to decipher the signal it wants. Apparently, when a receiver operates in this less certain environment, its messages to the servos slow down, so the servos respond more slowly - I guess the protection circuits which make certain that it has the correct set of digital info-bits, take a little longer to get "certain".

erbroens

Our club is debating right know what we are going to shout instead of "interference" when the plane crashes....


Seriously, we are also curious how this system will interact in a crowded field with multiple brands of SS systems... at least Futaba reported
that there was some testing done on this subject and they all worked well on their FASST SS page.

Enrique

SAP_2000

How about: "REEBOOT"

jonkoppisch

My Feedback: (162)

Or "Blue Screen".... Wait, that's only on the 14mz

ravill

My Feedback: (11)

I know the clubs are looking out for the safety of the club but.....

If Chris Huhn and John Redman can fly their speed demons at, arguably, the largest jet meet in North America, repeatedly, then I think your club should welcome the technology with open arms!

Raf

garrett_mcdonal

Hi Raf,

The question isn't so much whether one or two guys can fly at a jet meet with 2.4 radios along with a number of other non-2.4 radios but what happens if you get 8 or 10 people flying at the same time with 2.4 radios.

The only reason I asked specifically about Florida Jets was after seeing in an earlier thread around frequency control of 2.4 radios at FJ that organisers were expecting maybe 15 or 20 people to fly with them. Of that number, though, it may have only been that 2 or 3 were flying at any given time.

Regards,
Garrett

Steve Collins

My Feedback: (8)

At times, there are 5 or 6 of us (sometimes more) simultaneously flying T-Rex electric helicopters, all on Spektrum 2.4ghz radios, in a metal roofed warehouse. Receivers are never more than 2 inches from the motor, the ESC, all that spinning metal, not to mention that static generating belt that drives the tail. All of these components are encased in a carbon fiber frame. I can't imagine a more hostile environment in which to test these radios. Never a glitch, not ever! Nothing but rock solid performance.

If there were a 10 or more channel 2.4ghz radio available, I would not hesitate to use it with my jets.

WHMC

My Feedback: (15)

I think the 2.4 guys should identify themselves, as club members, etc then if to many guys are flying have a bottom hook on the board for 2.4. This would be for flight station availibility. The process is waiting for the maximum A/C in the the air, not a channel. Many clubs restrict how many planes in the air!

kyates

just keep it below 40 airplanes in the air at one time and you will be ok

Silver182

My Feedback: (2)

garrett_mcdonal

The current plan is to add some new slots to the frequency board for SS radios just to track how many are in use at a given time.

By the sound of things, there have not been any practically observed anomalies with the new radios. In the event that the frequency sub-committee of the Aust national body releases additional material on the current discussions, I'll post it here in case someone is interested.

Regards,
Garrett

PowerBoxDanny

My Feedback: (47)

I fly my Comp Arf Lightning on 2.4Ghz Spektrum and also my F-15 since the DX-7 came out with zero problems and superb resolution..Period. Will never go back to 72Mhz. It is going to be obsolete technology within one to two years.

growingupisoptional

I know one of those techincal wizards at National level and I know that they are going to send one of the wizards on a $5000 junket to the states to a 2.4ghz convention.
$5000 from your MAAA pocket that really doesn't need to be spent. Haven't these people heard about teleconferencing!!!!!!!!!
If the AMA approves the use of these units I don't see why the MAAA has to go thru all this pointless research again, other than to make themselves feel important.
The spectrum is clear for use and the 2.4g systems work. What more are they going to find out!!!!!!!

The post above is more than enough. If you fly 6 T-rex's on any radio systems without glitching your on a good thing.
And I have never seen more than 10 planes fly at once and that was on an no holds barred kill or be killed combat carnage session.
Go back to your comittee and tell them not to worry so much about things that don't affect them and worry more about getting the new radio past the minister for war and finance.
Not having a go at you as you are asking an honest question. (also I may end up in canberra) ;-)

The question should be put to the MAAA why they are wasting our money!!!!!!

Sparhawk

I highly doubt that. When everyone starts jumping to 2.4, I am worried about one thing: A pilot starts treating a 72Mhz radio like a 2.4 system and forgets that he can't just turn it on whenever they want to, possibly making for a very bad day for someone else. Until SS sytems can give me 14+ channels, I am not about to purchase a bunch of new receivers to replace my old ones either. Thanks, but no thanks, I will stick with my MZ for now.

Spar

jonkoppisch

My Feedback: (162)

I think the main advantage of SS is Peace of Mind!!!! Everyone is going to be switching back and forth for awhile. If they can't remember to grab the pin now there's no doubt in my mind that they wont remember to grab the pin when they have both radios.... The main point is, that if I'm on SS... I DON'T HAVE TO WORRY IF THEY GRABBED THE PIN OR NOT

If you are on SS and don't grab the pin, no big deal. You're not going to get accused of shooting anyone down. The most they'll be able to accuse you of is not being a member

If you are on 72 though and don't grab the pin. It could cost you way more in 1 incident than a dx7 and 5 SS receivers...

What may be more troubling is that with the new SS stuff, a lot of 72 items will be sold. Many people will be buying up all of the used stuff for sale because it's so cheap. They'll end up with a lot of different frequencies with multiple planes on different frequencies. It will increase the chances of the guys on 72 grabbing the WRONG frequency pin which could result in a lot more shoot downs in all of the clubs... It's bad enough when you have 1 frequency let alone 5 or more to keep track of...

Like I said.. Peace of Mind. If you're on SS you wont be the 1 shooting anyone down or being shot down. You wont even care if everyone grabbed their pin before they went to fly You will have to think of a new excuse to yell for interference though (you can't yell "who turned on") [:@]

F106A

My Feedback: (2)

I'm curious how long will 72 Mhz be available if there's this mass migration to SS. I'm sure there's companies out there that would love to get these frequencies. I'm not an FCC expert, but I think their philosophy is "use it or lose it". If everyone is jumping ship to go to SS, AMA is going to have a hard time defending 72 for model aircraft use.
BRG,
Jon

jonkoppisch

My Feedback: (162)

I don't think that everyone will switch, but it wouldn't surprise me if 1/3 of the club members have switched over within the next 1 1/2 years..

digitech

My Feedback: (10)

fubar?

c/f

My Feedback: (1)

I too doubt SS takes over the world, there are many 2.4 G third world junk that do not adhere strictly enough to the FFC regulations for that Freq. Were'nt HOME cordless phones 2.4G now 5.8G?Hmm should have been the cure all??? Ever read the lesser restrictive FCC rules for amatuer hour with the 2.4G? versus the stricter DO NOT CHANE a TX crystal rules without a certified technician of the 72MH band?

I think this from our own AMA board member sums it up best :

General comments on thread

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This thread has grown and grown, and gotten off topic more times than any of us care to count.

I'd like to make a couple of statements that I know to be correct and may help some of the discussion that has recently taken place. Most of you know I don't typically reply to questions posted in threads. So, if you want to ask a question of me the best thing to do is to e-mail (not PM) me.

DSS systems operating in the ISM band of 2.4 GHz (like XPS and Spektrum) are required by band rules to avoid collisions with other systems. This virtually eliminates the possibility of a system causing a problem with another system. It does not matter if the system hops or sits on one or two frequencies, a hoping system (following the rules) will not hop to the frequency of a system already operating. A Direct Sequence system will not turn on on a frequency already in use.

Video camera systems are a problem. It is NOT the RC system causing the problem, it is the video system. Many of these video systems being imported are far from legal. They often operate on too wide a band width and most operate at illegal power output. If you want to operate a video system, get one that operates legally and properly.

DSSS/FHS will be long debated and different manufacturers will do it one way or the other. Some find advantages to one way or the other. In general there is no clear-cut, overall advantage to either scheme. It is the spreading of the information and encoding of the information that makes spread spectrum work so well.

My final advice to all of you...purchase what you feel fills your needs the best; just as you have probably already been doing with your 72 MHz systems. If a complete transmitter, see if it has the features you need, see if the programming is what you want, see if you like the feel. If you don't have a problem with 72 MHz you probably don't have a real reason to switch. If you like your current transmitter and don't want to change but want to go to DSS, than wait for a module system to become available, but don't slam others that may not want to go that route.

The really neat thing about this sport/hobby is that it IS growing, new technology is available to us on an almost daily basis; that makes it fun for many of us. As each new product is introduced you have to decide if it is right for you.

Have a wonderful holiday season!

Steve Kaluf
AMA Technical Director


"If you don't have a problem with 72 MHz you probably don't have a real reason to switch"

As for me I will enjoy using my high end JR radios with a quick module swap to operate on any of the legal freq, AND I cant wait to feel the more connected feel in which the SS module is advertised to work better than the OEM, PCM operation setup itself.

garrett_mcdonal

Growingupisoptional,

Yeah, I'm aware of the money being spent to send an MAAA rep but that's a whole different question. Last time the committee met, it was basically agreed that the radios can be used and we'll just keep tabs on who owns them and how many overall Txs are in use at a given time. The one that actually bothers me more is the question about park flyers on 27mhz being allowed to fly at the club field.

What do you fly? Reckon you will end up here? My club will be laying a 140m sealed strip and doing a major upgrade of facilities this year. At the moment it is rough grass and short but I was flying a Super Reaper from it for some time. Once the new strip goes in it should be long enough to drag out a couple of other models.

Regards,
Garrett

rhklenke

My Feedback: (24)

Actually, with the Spektrum modules for the Futaba and JR radios, you'll get EXACTLY the same locked in feeling that you get with these radios in PPM mode - the module simply converts the PPM output of the radio to digital and transmits it via 2.4 GHz. The frame rate and resolution are the same as with a PPM RF link...

Bob

rhklenke

My Feedback: (24)

You know, I've heard a couple of people who have said that, but all I can find on the 2.4 GHz band is that its "unlicensed" and "unregulated" (words used on the FCC website about the 2.4 GHz IMS band). I've also read that the "guidlines" say that 2.4 GHz band devices should "expect" interference and be able to deal with it.

If anybody has a pointer to *actual* FCC rules that say that devices in this band must not cause interference to other devices in the band (especially official FCC regulations to that effect), I'd really like to see it. In the mean time, I have lots of evidence that for cordless phones, Bluetooth, and 802.11 devices, that's not the case in the real world...

Bob

c/f

My Feedback: (1)

BOB,

Thanx but I knew that and why I put in the PCM wording, You get failsafe features of SS via PPM, without the delay of PCM encoding.

rhklenke

My Feedback: (24)

I'm assuming you're refering to this on the Spektrum site:

"Best of all, the DSM2 Spektrum Air Module System operates faster than most conventional PCM radio systems currently available, giving you that all-important locked-in feel and precision that is so critical."

I think that the Spektrum stuff is great, but this is a bunch of hooey, for lack of a less polite term. Yes, the Spektrum system sends packets faster than the radio in native mode, but since the information CAN'T be updated until the next PPM stream comes out of the transmitter, its just sending the same thing over and over.

Furthermore, I'd be willing to bet that the PPM-to-Spektrum encoding takes as long, or longer than the native PCM encoding of the radio, and even if it doesn't, I guarantee you that its not enough of a difference that a mortal human can detect it.

Pure marketing hipe - but they're entitled as well as everyone else...

Bob

VLAMGAT

Bob,
You talk to much sense here, no kid likes being told Santa aint real.....
Your obeservations are very real in the real word.
When Santa is gone and the toys break they will blame it on each other. The only viable 2.4G scheme is FHSS for airplanes. Yes the FCC rules say they must coexist but when they do not, and they will, the result is a missile not a "Retry" dialog box.
The asumption that in consumer electronics they are much the same is true, the law says to reposition our equipment if you experience problems. It does not say you wount ever lose a connection....
At this point it is possible for anybody to jam a military secure satelite with as little as 1W if they know what to do, and its not much. Be real...
Jake Beans