luckyy

My Feedback: (2)

Doesnt DSMX fix this Problem?? JR and futaba were both having lock out problems FACT!

Prop_Washer2

My Feedback: (26)

It's a wave length issue, 72 million cycles per second, versus 2.4 thousand million cycles per second, the later's wave lenght i.e. "cycle size" is much smaller, thus the shorter antenna's are "tuned" to the smaller pieces or cycles for that one second time period. 2.4 GHz can also be compared to "Microwave"...

But what do I know, I just work for NASA, albeit on a bit more complex stuff than microwave or 72 MHz...

sideshow

My Feedback: (11)

We bow down before you.

bevar

My Feedback: (27)

So I guess the next time my toilet backs up, I'm gonna call a heart surgeon. After all...he's just a plumber too using your logic.

Beave [sm=72_72.gif]


[quote]ORIGINAL: sideshow

bevar

My Feedback: (27)

Billy,

I was thinking about that after you told me that JR was there upgrading everyone's transmitters to DSMX. Then it hit me. Even if you have a DSMX transmitter, you have to have a DSMX receiver for it to work. Unless everyone changed their receivers too...they were still DSM2.

So why this year did Futaba seem to be having the lion's share of radio failures?

Beave

rctech2k7

My Feedback: (1)

If you install additional antennas considering best receptions (without electric conductor close by or blockage), you’ll get the same signal. X,Y (90-deg) position of antenna you get the full area, you can add Z to make it 3D and position the Tx ant to Z in order Z to be useful. You can also used coax to expose ant as long as it’s properly grounded to Rx common earthing and also ground the base of ant. The length of the ant is based on RF wavelength, the higher the freq the shorter the wavelength or once cycle is, so you don’t need to be longer and smaller than that otherwise your inviting lower RF to conduct to longer ant and higher impedance to designed RF at shorter antenna since this kind of ant are mostly propagating electric field signal….

Prop_Washer2

My Feedback: (26)

[quote]ORIGINAL: bevar

So I guess the next time my toilet backs up, I'm gonna call a heart surgeon. After all...he's just a plumber too using your logic.

Beave [sm=72_72.gif]


You might do that, but your toilet may get a triple bypass, a few days in ICU and you'll get the bill..!! All seriousness aside, I have fairly extensive training and experience with good old microwave and longer wave signal propogation and reception. There are other RF "Experts" on the board that know a helluva lot more than I on the subject. It's not my area of expertise per se, bu I am quite familiar with it...

Prop_Washer2

My Feedback: (26)

Duplicate

bevar

My Feedback: (27)

That's pretty funny!

I think this particular issue is specifically happening at the 'Nall because of frequency saturation. Sure...2.4 is better than 72 or 27 IMO, but like everything else out there...it is not perfect. Airliners, rockets, space shuttles ETC all fail and crash now and then too if you think about it and those all carry a technological threshold so far above our systems you can't even measure it.

I am sure egghead out there is working on the "next gen" of radio tech for us to use some day but for now "it is what it is".

I guess if someone wants 100% reliability and safety, they need to stay on the ground.

Beave

Meesh

My Feedback: (135)

The name of this thread should be changed to "2.4 Problems at Joe Nall"

VF84sluggo

My Feedback: (55)

Yes, as the OP, I agree. That name would have been more to the point...change made!
What we'll never know here is if Shui's crash would have happened in a non-saturated environment. Was the 'metallized' plexi a flaw that would have led to a crash once the jet got out a good distance from the radio, regardless of the number of radios in use at the time? Would remote rx's have mitigated this?

If in fact Futaba had more problems at Nall, is it simply due to more Futaba users now, and thus a higher statistical chance of Futaba being involved, as has been suggested? Or. in a very "crowded" 2.4 RF environment, are we seeing the weakness of a setup that uses a receiver with only whisker antennas vs. a one with a remote rx array, especially as the jet reaches what would be the max range in-flight? If there is no difference, were there just as many JR/Spek issues at Nall then, ones that we have not heard about?

Finally, I'm with CraigG here: if the solution for a Futaba system is to just make sure you've got some antenna exposed outside the jet, then I'm for the remote rx array setup.

DougV

Or maybe the receiver or radio failed, the battery disconnected or perhaps he made a mistake?

Doug.

Meesh

My Feedback: (135)

Thanks Sluggo!

Floatplane

My Feedback: (67)

Any radio antenna when put in proximity to metal or other components that reflect or absorb RF can have issues.  I try, when possible, to mount my receiver (I use Futaba and Spektrum) in a place where the antennas are opposed to each other and only come into contact with the side of the fuse (in a wood frame) or I try to let them hang free when space permits (opposed to each other).  The long and short of it is that no manufacturer can say that they totally eliminate interference.  There are too many variables.  And to boot, that is just if you are looking at other sources from transmitter causing interference.  Phones, microwaves, Bluetooth, Portable Wifi, and other things emit to some extent on 2.4.  So like any radio link, it is unfortunately subject to loss periodically.  This is an RF issue, not a Futaba, JR, or xyz issue...

RealFly

Sorry, I posted under Floatplane (initially) my buddies log-in.  Direct all replies to me on the post....

VF84sluggo

My Feedback: (55)

You're welcome...it is more to the point of the intent of my original post/question.

But, as DougV points out, as have a few others, there are so many gizmos and gadgets in these planes, who knows where the actual failure point was? What's next, crash-proof "black boxes" for post-mortem analysis? Hmmmmmm......

As Boli said, if we want 100% reliability/safety, stay on the ground...just as the Safety Officer recommended

George

My Feedback: (57)

The smaller Wea. RXs have the "whiskers" as you call them, and the larger 12-XX series have two antennas as well, but they are connected with SMA connectors and they have differing lengths and options.

In my Mibo, I installed one "standard" antenna that ran ran forward and one longer adapter and stump to the rear, and vertical to exit the fuse where it looked like a scale feature. You can see it in the middle of fuse about halfway back.

VF84sluggo

My Feedback: (55)

Hey, I was an Aero major, not an English major...it was the best I could do to try and convey what I was talking about

Thanks for the info and pic. Nice jet!

Moerig

Truth be told satellite RX's that can be put in optimum places are better no doubt. But this is not a plug for Spektrum as the FASST technology probably is better. So an Array of FASST RX's would be optimum IMO. This is possible using SBUS and some RRS designs for SBUS.

RCFlyerDan

My Feedback: (54)

LOL>>>>>>>Has to be flown to have an issue!!!>>>Sluggo worries alot and is influenced by others' too much!!

franklin_m

With the above statement, one of two things must be true: either the published range check procedure is not reliable, or something else caused the crash. Absent telemetry, there's no way he can make this statement. It leads one to believe that the antennas were partially obstructed. Ok, with 2.4 that is indeed an issue, but what was the orientation? if it didn't have that piece of plexi blocking the signal, then it wasn't that now was it? 23 years experience attacking electronic RF systems tells me it's something else. The system, all systems, have limits. The manufacturers / distributors have yet to tell anyone what the design limits are....and they've got incentive to continue to keep that quiet. For all the ad dollars spent touting the robust nature of 2.4, to come out now would create havoc in their marketing / consumer relations. Don't kid yourselves, there's huge dollars involved, therefore huge incentive to try and blame something else rather than the most obvious - a crowded spectrum at the site and radios that are not so robust as advertised. Remember Occam's Razor - the most simple explanation is usually correct. From my post in another forum:

There's any number of good sites out there that demonstrate how spread spectrum works, the different schemes and, most importantly, how the signal coding works.

Dabigboy pointed out above that there are limits to this system. Despite what the distributer is saying, physics is physics. There's a limit to how much signal to noise these can tolerate, how many data chunks a receiver can miss, and the simple fact that there's a lot of RF energy in the 2.4GHz spectrum, from a variety of sources. Every time a piece of a spread signal is at the same frequency at the same time as something else, there is interference. More transmitters, RC or not, then more opportunity for overlap at any given frequency/point in time.

Regardless of whether it's DSSS or FHSS, there's only a finite number of frequencies and a finite number of coding sequences. Even if the number of coding sequences is large, at what point does the number of transmitters start to load up enough points in time to the point where a receiver locks out? How "random" are the random code generators? How long does the receiver processing take? I've seen any number of systems overloaded just by making a receiver spend too much time trying to sort out what's real and what's not.

Like I said, I've spent an entire career finding ways to hammer RF systems that were much more robust in their designs than RC receivers, and there's always a way. It doesn't always require fancy equipment either. However, one thing remains true....the more dense the RF environment, the easier it is to knock down a system.

Regardless of what the marketeers say, there are limits to these systems. I just wish they'd share them so we can make informed risk decisions on when to fly and when not to fly.

AndyAndrews

Why doesn't any of this affect us using 2.4?

http://en.wikipedia.org/wiki/Electro...nce_at_2.4_GHz

VF84sluggo

My Feedback: (55)

It's true! But as a jet newb, what can I say? These things get farther away, faster, and with more signal-blocking guts, than my prop jobs. So, it's just you veterans yankin' me around

Seriously, I do enjoy the 'education' part of this hobby. But, I'd like that education to be as much as possible in the "classroom" and not by trial-and-error!

RCFlyerDan

My Feedback: (54)

You can only do so much hanger flying! Sometimes, you just have to go burn some fuel!

VF84sluggo

My Feedback: (55)

Yes indeed, Dan. Fixin' to head out the door to fly this P-51/DLE30 airplane some more. Our 'jet' sized field is off-limits right now.