Gordon W

So aren’t all Futaba 2.4 setups using FASST?

Gordon

BaldEagel

Could be a Futaba set with a Spektrum, Act, Jeti or even a Weatroics module in it.

Mike

hyperdyne

My Feedback: (6)

Spektrum uses a DSSS (direct sequence spread spectrum) system. Whereas FASST uses frequency hopping. Both are bandwidth spreading techniques. With all things being equal, DSSS has a better jamming immunity over frequency hopping. That is just how it is. If properly designed, DSSS will offer better interference rejection.

However, there are also other factors that come into play, such as spreading gain, bandwidth, power, etc. The worst offending signal in the band that can unlock a spread spectrum receiver is a narrowband jammer (pilot, carrier, whatever). So anything in that channel that is narrowband will most likely be responsible. It may be the choosing of the band in spektrum that is its undoing, but from my understanding it is using 2 channels to send information. So you would have to have jammed both channels, which is unlikely unless you have some broadband RF jammer in the area or the channels are adjacent to one another.

In this case, multiple receivers don't help since they are simply despreading the same jammed signal. Only way around that is a beamformed antenna setup (that aint cheap!).

I use spektrum myself and I believe it may be the initial channel selection (or something like this) that may be causing issues. I trust DSSS over FH (just look at the math). Heck, GPS and other comm systems use DSSS also. If it's good enough to guide a bomb to its target in a hostile RF environment, its good enough to fly an RC plane. But as I said, only if it is implemented the right way...

tenacious101010

My Feedback: (97)

gunradd, what field do you fly at in Tampa? My son and I have been flying for several years at a local club and have found one particular area of the field has a very large proportion of glitches that could not be isolated to the cause leaving transmitter/radio problems the suspected culprit. One of the incidents was with Futaba 2.4.
Denny

Dan M

My Feedback: (1)

hey

what field do you fly at ?

thanks

Dan

edit : i didn't see the above question , forgive me .

Robrow

Looking at the Weatronics 2.4 system......I am no expert but is it better to use 81 channels rather than 2 ?

Rob.

FILE IFR

Do you think it's possible there is a twisted loser in the Dunsfold area with a hand-held jamming device amusing himself at the cost of the club's modelers?.. there have been 2 or 3 cases like this with 72 megs in the USA over the years. [:@]
Is there a certain time in the day this happens?

.... Just a thought

skyhawknut

My Feedback: (3)

I don't believe Gunnrads problem was a radio problem - he was using a reversing Y on his elevators when it went in.

Those things are bad news.

Mono

Very interesting, all these problems sounds very familiar.
Our club in the south of Sydney Australia had major problems with Spektum JR 2.4Ghz about 18 months ago. At least 15 aircraft lost in 8 to 10 months! We had no problems on 36Mhz!!
All different types of Spektum DX-7, DX-9, JR10X with modules.
After much investigation some were operator error, some battery charging. Nothing conclusive.
4 radios were replaced by the distributor with no explanation. To be fair to JR that was the only type in use.
Adjacent to our site we have radio transmittion towers with micro burst facilities.(at last count 61 transmitters and repeaters)
I have personally wittnessed the failure of a 100cc model on 2.4g locking out and not going in to failsafe. (very scary)
Amazingly all the problems have stopped and we have had a good run lately, no problems at all.
JR and Futaba system are both performing well.
The moral of the story is don't blindly believe the advertising. There is no such thing as an interferance free radio!

gruntled

Yes, Spektrum has an advisory on their page against the use of amplified Y cables and electronic reversing Y cables:

http://www.spektrumrc.com/Community/...Practices.aspx

gooseF22

I have seen environments that cause interference in both types of spread spectrum algorythms.. No radio device is ever foolproof, even the military radios. When narrow band transmissions are used, whether it is frequency hopping or wide bandwidth, you can only transmit so much power within the duty cycle of whatever transmitter you have.

There is a couple major types of jamming. There is coded and noise.. Noise is simply random interference or interference that the receiver sees as random. The coded jamming is when the receiver thinks it is getting valid signals...

Examples: PCM lockout due to noise: it loses the modulation signal and goes into lockout.. It still may see the signal, but it cannot recognize anything coherent. Sometimes it may try to intrepret, but usually it is a lockout of some sort.
coded: the receiver sees a signal that it recognizes or partially recognized and tries to act on it... (servos flailing...) (two 72 transmitters on at the same time) You may see both, but thats the basic process... the 2.4 Radios get around this background threshold noise by rasinng the signal above the noise, aND, the timing/GUID's of the pulses keeps the receiver looking in the proper sequence or code. Doesn't matter if its frequency hopping or pulse mapping.. I am not advocating either, but we had better success in the uav lab with DSS because it had a narrower band higher RMS under the curve power and the noise we encountered were from other than 2.4 bands bleeding over into ours using field Microwave communications.. When we brought out a jammer that was a broadband noise jammer wiith sufficient power and bandwidth, we could shut down any radio.. But we could shut down a 72 as well because of the really noisy frequency harmonics. Airplanes have this problem all the time. Eventually the signal can burn through as the power of the transmitter rises above the threshold or moves frequency just enough to come out from under the signal.

In the case in England I would suspect there is directional microwave communications pathways in play, or railroad comm devices that are high power and bleeding over into 2.4 via harmonics, 1.2 .6 4.6 GHz.... I have worked military devices most of my adult life in the military, and I have never seen anything that was foolproof, but the stuff with smarts built in are amazingly better.(over simplified)..

Frequency hopping can drift or be covered with a broad signal, and Wideband can be covered with a powerful single freq signal but takes more power... two ways to skin a cat, each with pro's and cons...

What we havent discussed much is the reciever.. the heart of the matter. the latter generations of 2.4 receivers are much better at discerning the signal above the noise. Example is the 4 receiver spektrum... The funny thing, is that you could move the receiver a number of feet in any direction, and it goes away.. stuff like that usually is something directional. When a signal is directional, it can radiate more power in that realm (flashlight versus light bulb).. The transmitters are radiating in a donut, so it wont take a tremendous amount of directional power to overcome it if the frequency is right, no matter how much it hops or how much power peak it has.. nothing is foolproof.

I personally fly JR, and that was based on my experience, but I would not be afraid to fly the FAST system either.. If there is problems at your field, try to make sure your setup wasn't the culprit first, as most crashes can be explained eventually. there has been some bad AR500's out there. There are some AR7000's with antennas that have come loose, fast antenna that was broken... Transmitter wires broken internally, dead batteries, switches... go there first, but again realize the environment we fly in is hostile, but we do pretty good overall..

hyperdyne

My Feedback: (6)

When a DS spread spectrum signal is despread at the receiver, it basically turns the wideband signal you wish to receive into a high SNR narrowband signal. Likewise, if you have a narrowband jammer in the same band, it goes through the receiver and spreads the narrow interferer over the entire bandwidth of the input signal, basically decreasing the SNR of the received signal. And a broadband jammer will be despread into a narrowband signal, but the orthogonal coding on the data will cause it not to lock onto it. So a strong narrowband jammer (whether it is pulsed, continuous, other) in the signal band can wreak havoc on the RF link. Same thing happens with GPS (it is relatively easy to jam and has a much larger spreading gain than our radios).

The one thing I do not like about JR/Spektrum is their reacquisition after a loss of signal. They should be able to lock back up to the signal immediately (well under 500ms), but I have had receivers that take seconds to lock back up. That is unacceptable and just poor engineering. The only reason for an untimely signal reacquisition is because the signal is being jammed! And if that is happening then the link is not smart enough to switch channels when this happens. The FASST system may lock back up faster (I'm not sure), if it did it would be much more favorable even with the FH scheme. Basically, both are fine for our application, but which one can recover faster from a loss of signal would be my new favorite.

c/f

My Feedback: (1)

Socomon, your not getting it, A small room with a wireless router would be the best enviroment to fly because the TRANSMITTERS seeing each other play nice together this is called collision avoidance and why all the tests with 40 plus TX on is a small proximity to others see each other and of course work.

The above RCG thread came from SEFF as it was a 1500' flight line and weird crahes occured, that no way could have been power since most were proven at home feilds for months.

Japan Radio JR, will have DSM3 which is FHSS, (new X11) BUT according to the men in RED, it will be exclusive to Japan market and not exported, Reason being that Japan airways DO NOT ALLOW the use of 2.4G with DSSS. As I understand it, the DSM3 is a Spektrum created processing format for JR exclusive use. So now we have DSM1, DSM2, DSM3....

So seeing as 2.4G is a world wide format, one just might have to get a Japanese Rosseta Stone.

BaldEagel

At our field we have high power burst transmitters on either side of an estuary, the points of origin cross our site in two places, both of these areas create glitches in PPM and some interferance in PCM, I bought a Graupner IFS system and it locked out consistantly in these areas, only flown once, Spektrum is occasionally having problems in these areas also, myself included, the four pilots on Futaba FASST have not had any problems whatsoever, my FG12 on FASST has been "Rock Solid" since day one, my Spektrum gear is now confined to small expendable airframes.

No matter the technicalities in the real world situation that I fly in, FASST seems to be more reliable.

Mike

johnls

I don't think its the twisted loser syndrome, I think Mono has summed it up well. I know there are microwave links, running across the airfield. these are part of the security camera system. I also know there is a company that does some form of secretive government work, and it involves research using radio frequencies. Their work is not to a set schedule and I have not personally experienced a problem (on 2.4, although I have had many problems in the past with 35mhz), until now. Thus my naive belief, up until now, that I had a bullet proof radio link.

gunradd

My Feedback: (9)

I fly at baycity flyers or area52.

Yes I did have a reversing Y for the elevators that might have caused my crash still dont know but guys using XPS have been hit and also another guy lost 2 planes now using futaba. Also when mine flew away I had no throttle control and the reversing Y does not explian that part unless it somehow messed the receiver up. Its hard to say what got mine because it sat for over a week in the summer rain before I found the thing. The receiver lipo was blown up like a ballon but I think that was because it was still plugged in and draining power after the crash. Also nothing explains that when in fail safe the motor should have been off and the controls are not supposed to move. The guy using the XPS system also had uncomanded movements not just lost signal. The messed up part is I used a big old trainer with a video camera in it to find my plane and I was taking off from the feild then riding in back of a truck while flying and I would fly the plane to almost out of site then bring it back and I didnt get hit a single time.

PacificNWSkyPilot

My Feedback: (19)

More than just that, Roy. The Spektrums in the UK, Africa, and probably some other places are required to be "turned down" to a fraction of our USA outputs.

PacificNWSkyPilot

My Feedback: (19)

I sent all of my Rx's back to the factory for upgrades, and their response time is excellent, just about at .50 seconds, in fact. I don't know what you reasonably expect them do do when the signal is being jammed. After all, a signal that's jammed is essentially a malicious-based signal that's designed to PREVENT any signals getting through (reacquisition). Signal jamming is simply a recreated (and usually amplified) 'natural' occurrence, so when one is encountered out in the world locally, you've got something that's fighting your radio, intentional or not.

I started out with stone-knives and bearskins and AM radios. These are as close to perfect as we have so far, and they are always getting better. I know they will continue to improve, but for now I consider them to be nearly perfect.

I did discover a small but scary problem the other day when I tried to use a Cermark switch, and my Spektrum started going wacky, lights flashing and not connecting properly. As it turned out, I had not checked closely at the Hobby shop and it was hanging on the JR/Hitec rod where I usually grab them. But the switch was made for a Futaba, and I'd grabbed two of them. I plugged in another Cermark switch for the Spektrum (JR / Hitec) and it connected solidly upon turning it on. These switches look identical, folks, so remember this. I think the Futaba connectors have the flange on them, which clued me in upon inspection. But my Receiver somehow allowed the flange to fit with no extra effort when I plugged the Futaba switch into it.

PacificNWSkyPilot

My Feedback: (19)

By the same token, Don't put too much stock in what Chicken little is running around and screaming....

You too could have a twisted individual jamming you, or a dozen other explanations as well.

I've always wanted to ask a question of the folks who fly next to ACTIVE high-powered microwave and microburst towers.

Why the HECK would anybody with a lick of sense even THINK of taking such a chance with months and years of hard building work? Why would you take your radios and your planes into such a DEVASTATINGLY POOR ENVIRONMENT FOR THEM?

That's like throwing a chicken onto an LA freeway, and after the ensuing chaos and the ultimate demise of the poor chicken, declaring the chicken to be poorly designed.

As long as you're doing this, you might as well invite some duck hunters over for some practice shooting....if you can keep the planes flying long enough for them to load their shotguns.

This sounds familiar, all right. Ever heard of the Darwin club?

LOL

BaldEagel

To answer your question, because its difficult enough to find a field to fly on in the UK our land mass and spare land is very small compared to the US and the Antipidies, the field we use is on Marsh land and yes we share it with the Duck hunters, so your analogy is quite close to the truth.

Perhaps you are a founder member of the Darwin Club. LOL

Mike

PacificNWSkyPilot

My Feedback: (19)

Naw, they are pretty much all dead now. That's sort of the idea with that club. It's like what most of YOU guys would be if you were inside the planes you endanger. Improving the gene pool through personal actions....

Gee, I hated having to explain that. It almost took the fun out of the joke. Almost.

And nothing you said made any sense or gave any reasonable explanation as to why anybody would fly in such an environment. I'd hang my planes on the wall permanently, or look VERY hard for another field. When a club I belonged to splintered and the second club moronically put theirs right next to ours (I mean, nothing but a string in between us), I left and told them the same thing. They wouldn't even share Frequency info!

Flying in such a place is senseless. Oh, and there are groups that do it here in the USA too. Those groups were actually the primary focus of my statements, I wasn't actually thinking of anybody across the pond.

Your reasoning is a little better. Not much, mind you. But a little.

hyperdyne

My Feedback: (6)

Reacquistion after signal loss is different that reacq during jam. I cant believe all the time I am being jammed with boomer signals. Most times signal loss is intermittent and a reacq should be pretty fast. I would love a 500ms reacq time, but most spektrum receivers dont do that.

And yes, sending the Rxs back you can get the 1.6 version that acquires faster. But why didnt they do that in the first place? I mean, reacq taking 3 seconds is death for an RC plane. I've had many planes go in from "death by Spektrum". I figured out which Rxs not to use, and it was a costly lesson. But why did it take them so long to fix it? If that is something they couldnt figure out before, then I dont trust them to make a proper DSSS link.

gruntled

This strongly suggests you were not setting your planes up correctly to begin with.

RobinLeblond

TexasSkyPilot,

I somehow understood why they are taking "a chance" to fly over this kind of place...
Here in Quebec we have "more then a lot" of trouble to find a field since our gouvernment "officialy" forbiding
us to use ANY agriculturale place to practice our hobby, and as most of the flyable place are agriculture
we simply do not have any safe place to fly. And we have to consider public (and neighbourhood) security
before our plane security (I meen by that : Better choose a risky place for our plane but far away from any
neighbourhood then to choose a safer place for our plane but right in a residential proximity...).

But still, you have a point : Why taking a risk when you know their is a risk...
Sometime we dont have a lot of options...

hyperdyne

My Feedback: (6)

Not really, you assume too much. The 6100 is a grand example of a terrible spektrum receiver. It was not a full range receiver, but you could never get a max range number out of Spektrum. Many of my parkflyers (and other guys planes) were lost to using this POS.

After I switched to the 6200 and 7000, problems disappeared. Hmmm, curious.

Being an engineer who designs and uses much more complex DSSS systems on a daily basis, I know more about them than the average joe. I just happen to call out a flaw when I see it. I still fly Spektrum to this day, but I also have some important issues I wish they would address.