Independent tests prove lack of frequency hopping with XPS

[RH1N0]

For info, I just posted links to some basic test data showing the signals from different 2.4 systems here: Specktrum Frequency Analyzer for RC!!!!

There are also some examples of interference from microwave ovens in the original posters examples and on the Wi-Spy web page.

[sweetpea]

Ok that explains a little more on the testing.....

I want to be clear.......

-the test involves a video transmitting device that operates on or near 2.4

-XPS works fine when the video is turned on first. It scans and moves away from that signal. (as we would expect all the 2.4 to do)

-XPS does not work when the video is turned on after XPS.

Could this be because XPS is using the first avail freq it sees (which seems logical).
Then it gets blasted with a signal on its primary freq which would happen to be the first freq in the order, and maybe there is some harmonics on the adjacent ones it tries to hop to. It can't find anything fast enough that is clear before its default timer goes into failsafe.

I would think the logic is pretty simple for the hop. At start up find the first avail signal. At signs of conflict move sequentially up in freq until you find a clear one or failsafe timer hits or something like that.

So questions I have.

-what is the failsafe timer set to or how many hops does it perform per second? and does it matter if I set the rx failsafe to the lowest setting or highest?

-How long does it sit at each freq it hops to before trying another (assuming it is trying to hop and can't find a clear freq)?

-**is the video feed so bad (strong, wide or whatever) that its blocking XPS from being able to send the hop signal successfully? (i.e. XPS talk of a slow increase of noise over a sudden burst that stays)

-How about trying a video feed at the far end of the 2.4 spectrum. This way XPS locks onto the first avail freq and the video feed is no where near....hows that effect?

-I think I've heard the same issue with Spektrum not working with video in this same manner.....since it too finds the first avail freqs. I have not heard what logic it uses for its second freq but I imagine its sequential as that is pretty easy/common to program. Also is the gap between freqs the same every time? I.E. meaning if during intial bind if the gap isn't say 25 that it must move the first freq and try again(this could explain the long bind times sometimes seen)

-FASST constant freq hopping.....what effect will it have when it hops through several of the video's taken freqs? How many used freqs before it is effected (knowing it hops fast)? Does it hop sequential as well or is it random and may continue to hop in the taken range?

**From what I've read on your results and replies on RCG from XPS this sounds like what is happening. XPS is waiting for the sudden burst to go away (as per their programming since it assumes a burst like that should be temporary). If it was a gradual increase the threshold would be met for a hop before the RX was swamped and unable to transmit the hop or met the level of the sudden burst where it decides to not switch thinking its a burst.


Ok so here is what I'm thinking at this stage: (let me know if you think I'm way off base)

So if this last part is true then one could take away that XPS decided that sudden bursts would not be that long and the risk of changing freqs on both the RX/TX getting the message and accomplishing was greater (be it time or the chance of not reconnecting) than waiting out the burst as far as loss of radio control. Thus they chose to wait it out. Going back to the fact they didn't anticipate 2 things......

1) the higher noise levels at numerous fields in the world (due to whatever is the cause). They probably had a base line that was lower than expected for worse case. These higher noise level fields are in the burst category as far as the freq hopping (just a guess)

2) customers trying to put outside R/C devices on their planes in the same freq range. Again putting the system in the burst signal strength category (this, I think all the manufacturers will be to blame on for not anticipating)

-----------------------------------------------------------------------------------------------
---in my hindsight it appears that floor noise levels where beyond what they expected to worst case at most fields (probably due to the last 2 yrs of strong housing/business development all across the country and the fact they are not a Corporation with easy access to fields and pilots all across the country for absolute complete testing so they sampled, which again is pretty common practice though not always desired) and these issues have caused a few problems to the system.

1) New antenna for places like Las Vegas
2) customer induced noise floors, by using video on a freq near 2.4
3) customers demanding the satellite rx's now (which XPS stated was a feature of the telemetry in the future). [I also think this reverts back to unexpected noise levels as extra rx's would help in this situation]

I stand by everyone in that this is one fault that I can't ignore. But in the same breath I can't ignore the fault of Spektrum and the low voltage issue (which hasn't been fixed, only bandaged by us, the modelers)

Now the consumer calls foul and tells them they want it to hop no matter what, at any sign of interference. Being aware that many thought this was the case from the get go since they did not understand the complexities of how any of the systems are wired/programmed as no company releases that kind of information in advertising [Noting that XPS original advertising explanations of hopping did not go into this much detail of how it worked as it was probably too hi-tech geeky for most so they generalized which is pretty standard]


Remember...... is my thoughts only, I have no proof to back it up. To me it just seems the logical approach and I could be wrong I also don't yet any experience with FASST, and since they are currently for Futaba radios only (I don't own any of them) I most likely won't get that chance

I know Xjet doesn't have the time nor money to do all the testing we would like......but it would answer more questions to see how the other 2.4 systems react to the same test conditions.

[3DDevil]

Someone wanted me to post how I lost my 90 size model with XPS... here is a post from another site...

Well.... my 90 size Extra is no more....

Went like this.... pretty simple really.... gassed her up... did a radio check all good... took off... turned right... did a slow roll... then she wouldnt respond... then it responded a little and then did'nt then again a little then did'nt... got further and further away (towards a major road)... and I then she rolled onto her back... I chopped the throttle and the last I saw of her she was inverted in a shallow dive for the ground!!....

I was worried that the thing may have hit a car. But we went and looked and couldnt find it at all!!... There is ARMY land near us, that you are not allowed onto because its a firing range... so I couldnt even go and look for it.... so.... a total loss at this point!!!..

My mate who is in the army is going to try and get me onto the land this week to look for the pieces.. be good to get my engine and some other parts back hey....

FLIGHT CRASH ANALYSIS...
ENGINE - Running fine
CONTROLS - on ground responding all directions.
TAKE OFF - Normal
TURN - normal
Then... loss of radio signal and intermitant regain of signal for a second or two then loss again..

Result... loss of control and loss of aeroplane... totally
As much as I hate to say it... I think it was directly caused by the 2.4Ghz system. I had changed nothing from the previous week, which had flawless results.??? Unless something came loose, which I didnt notice in the preflight???

Oh well.... probably back to 36Meg for me.....

MERRY CHRISTMAS TO ALL!!!

My batts were fully charged ENELOOPS....

The plane appeared to go into fail safe... but that is just the last settings that the servos were at... so....

one problem is that when the plane doesnt do what you expected it to, you add a little more 'stick' in the hope that it will respond. Then it does and reacts violently and much more than intended. So you end up chasing the thing and it ends up very out of control.

I used this system in my 90 extra to 'test' it out... I guess I got my answer... anyone want to buy a 8 channel JR plug in module? Slightly used!! Or have it for FREE!!??? LOL!!

[Flatlandman]

3Ddevil i have a crash that i would explain exactly the way you just did except remove 90 sized extra and replace with 50cc extra. It was flown with a pcm radio and rx . The cause of the "interference" was infact a low battery. Theres enough voltage for the rx to see a good signal and not enough power to move servos so no failsafe and no engine kill. I dont know how the battery went low it was check before the flight but never the less the battery was found to be defective in post flight/crash. Then the same failure was reproduced with new parts and the same intermittent loss and the same continuing of the motor running with no way to turn motor off, on a test of a new plane on the ground.

The only recourse i have to prevent another such failure is a new setting in the electronic engine kill switch for low voltage and or dual batteries. The plane is still going to crash with this kind of failure but the engine will be cut off and the plane will not fly around the sky for 2 minutes or more waiting to crash.

[jonkoppisch]

	Quote: Originally Posted by 3DDevil
	....... Well.... my 90 size Extra is no more.... Went like this............ But we went and looked and couldnt find it at all!!........ I used this system in my 90 extra to 'test' it out... I guess I got my answer... anyone want to buy a 8 channel JR plug in module? Slightly used!! Or have it for FREE!!??? LOL!!

With jd's new unconditional warranty you should be able to contact him and he'll give you a new free receiver no questions asked!!!! At least you'll have a full system to sell then, unless you want to try it in another plane

I lost my plane also, checked the batteries (running 2 packs, 1 was destroyed) and it was fine under load.

[Ed Hornbuckle]

	Quote: Originally Posted by notorious_benny
	Sue for what??? Its not illegal to dispute, debate,test anothers technology. Sueing seems to be the favourite pastime over there in the US.

Yes, its called the Great California Lottery...

Ed

[BoneDoc]

XJet, thank you for finally supplying the method of your conclusion. I for one, don't need a video to believe what you're saying.

What I want to see more than anything is whether the same problem would be encountered by Spektrum. If so, then we're back to square one. Especially if FASST locks up also brings everyone back to square one again.

FWIW, untill you have more / better evidence, you really should change the title of this thread.

Again, I do not own XPS, nor do I intend of EVER owning one, but in all fairness, the thread of this title either warrants better evidence / tests, or reveals a bias on your part.


Thanks

[50%plane]

Just an observation here, but I have yet to see X-jet's so called "proof". It seems like he's pulling the same stuff as he claims XPS is........... How about providing proof of the problem in XPS on the first page in the first post instead of 10 pages later and someone else's work...


I was going to switch to XPS when it first came out, but ended up giving up RC for a time due to work. Now I'm still flying 72, but might switch to FASST in 2008...


Chris



flame away...................

[exeter_acres]

50%....

no flames needed......

this entire thread is a "hesaid, he said" thread.....

no substance......

Mods, any reason to really keep this going??
the WHOLE thread is speculation

[ricoalonso]

Well, XJet promised to show his test results after the New Year holiday so why not just give him the chance? After all, if XPS will take the positive side of this thread, who knows, it may even help them to improve their product to 'near perfection'.

^R^

[RMaia]

	Quote: Originally Posted by ricoalonso
	Well, XJet promised to show his test results after the New Year holiday so why not just give him the chance? After all, if XPS will take the positive side of this thread, who knows, it may even help them to improve their product to 'near perfection'. ^R^

I agree!

By the way, from the descriptions already posted, I already have a plenty good idea of the facts happening... For me no video would be necessary to understand, although it would be an interesting thing to watch!

One thing is certain, at least for me though, XPS or no XPS, there's still a lot to be "discovered" about the current 2.4GHz systems being offered....

[ricoalonso]

We can all look at it this way...

XJet is doing a 'free' Quality Assurance & Reliability services to XPS and the XPS users. If the test results show the deficiency then XPS can use it to improve their product. If the test shows that XPS (hopping) is actually working then XPS can make use of it to further promote their product and all current XPS system owners will have even more confidence using their system. Either way, everyone will be happy .

^R^