Discussion So what is the industry changing news?

[borneobear]

Originally Posted by skubacb

XJet, you missed it again, and again, and again.

We are tired of you since you add NOTHING here. NOTHING. We understand how the system works and it works great.

I would not consider the following statement as NOTHING:

Originally Posted by XJet

The XPS will not hop when there's a sudden increase on its chosen operating frequency -- EVEN IF THE REST OF THE BAND IS CLEAR...

the protocol XPS uses for initiating hopping relies on the transmitter and receiver still being able to talk to each other.

If there's a sudden noise increase on the channel XPS is using then that communications ability is lost so neither end knows where the other end would be hopping and it fails -- even though the rest of the band may be clear.

If what XJet says is true, than that throws the argument in a whole new light.
The Rx and Tx has to TALK TO EACH OTHER before it can Hop???? Thats utterly stupid. Why the hell would it hop if they could still communicate???


At it amazes me how some of you still accept Jims word as the gospel truth, when clearly we have been misled.

I certainly bought the system because I thought it would channel hop when there is RF interference. But apparently it comes with "Terms and conditions apply".

And why do we keep asking XJet to prove himself?
Isn't it time that Jim proved himself to increasing evidence contradicting his claim of channel hopping??

[skubacb]

Again it is a twisting of the facts. The jumping is preemptive. IE it looks ahead to see what channels are clear and IF the noise floor is increasing it WILL jump to a new channel as necessary.

What you are getting is a twisting of the facts. The system works exactly as we were told it would.

I accept what Jim has told us about the system because what he has told us is what the system does. XJet has no claims to anything here. He did not design the system. He has no access to the code that Jim wrote, nor access to the code for Futaba or Spectrum. I accept what Jim says because no one has shown the system to work any differently than what he has told us.

Graupner after a very intense testing of all the system picked XPS. Not the other systems. Their testing verified that the system worked the way that Jim has been telling us it does. So why should I accept the word of someone who is not an expert about this system. Why should you?

[wrightme]

XJET has done NOTHING except talk. Even on flying giants, he has not posted any data.

Of COURSE a TX and RX should "talk" to hop. ALL agility systems need to know where to start and where to go next. Otherwise, they do NOT communicate.

Maybe you should go back and re-read the dialog about the hop issue. Until his post this evening, I never saw Xjet, OR JD claim that one isolated frequency would cause the problem, or ANY data to back up that claim. It would have been a good idea to actually POST the test data that was used for that claim. For instance, what was the db level that caused the "sudden rise" of the noise floor, and how WIDE was the raised area. XJET only comes back with "JD agrees, so I don't HAVE to show...."

[borneobear]

Originally Posted by skubacb

They have a fantastic reputation in Europe and wanted something that was the best (Germans).

XPS is German? Thats news.


I come here everyday to check on whether Jim has posted anything that will assure me his system will work as he claims, as there is evidence that it does not. His half hearted denial AND (at the same time!) admittance that he's system hops only under 'certain conditions' isn't at all assuring.

I don't really care what XJet says. What I care is to know exactly what weaknesses the XPS has, and how best to deal with it.
Until such time, my XPS Tx module and Receivers remain in my drawer collecting dust.

[E_ferret]

Originally Posted by borneobear

Until such time, my XPS Tx module and Receivers remain in my drawer collecting dust.

unless the drawer if of poor quality or really badly made, it should not collect dust, unless you leave it open.

[bjpaul]

From one who has been often accused of being a "fanboy" of XPS and even accused of "shilling", I have to admit that I find value in XJets postings.

Keep up the research and please post your testing results when it is complete.

Brad

[wrightme]

If XJET confined himself to providing information, I also would find value in his posts. His delivery leaves room for improvement.

[borneobear]

Originally Posted by E_ferret

unless the drawer if of poor quality or really badly made, it should not collect dust, unless you leave it open.

Termites?

[Julez]

Graupner after a very intense testing of all the system picked XPS. Not the other systems.

Care to elaborate on "the other systems"? Were there so many to choose from?
Remember, Spektrum is limited in power output in the EU (-->parkflyer range).

I would put it like this: XPS was the only choice for Graupner; their last chance. Either XPS, or nothing with full range.
They can't make money with "nothing", so...

[vampire67]

Originally Posted by borneobear

If what XJet says is true, than that throws the argument in a whole new light.
The Rx and Tx has to TALK TO EACH OTHER before it can Hop???? Thats utterly stupid. Why the hell would it hop if they could still communicate???

XJet is right. There are several threads (e.g. http://www.rcgroups.com/forums/showthread.php?t=688773) that discuss discrepancies of XPS claims and engineering facts.
Matter of factly XPS seems to heavily edit the XPS sponsored forum section to erase posted fact data. Not a very conincing business method.

One technical fact I noted already is that the XPS receiver seems to start eratic activity at a rather high voltage level: ~3.5. So single Lipo is out of discussion. And I would be casefull with small Rx batteries, especially NiMh types that show a high resistance.


@skubacb & wrightme

Unfortunely it's YOU that add nothing than nonsense

In fact in the other threads is has been proven by answers of JD itself that there is no preemptive look-ahead.
The switch is triggered once the noise floor rises above a threshold and then the Tx tell the Rx the new channel.
He commited that a sudden blocking of the channel (not the band) will prevent system from switching at all. It goes into failsave until the channel is again clear.
A preemptive look-ahed is in fact possible. E.g. the Rx checks the band during transmitter breaks (~80% of the time the Tx is off). Then a emegency switch sequence can be acknowledged with the Tx. So once the transmission is lost the Tx & Rx start the emergency sequence synchronised.
It's "just" software.
So it can be updated and probably will in some time.

Just for the record.
A collegue does HAM radio. Their club operates a 2.4GHz TV station that sends legally >10W RF power (antenna output ! not power consumption).
The station can be triggered on/off via radio link.

The station is about 5km off the strip were Peter Michels lastly lost his MD11 using 2.4MHz (but not neccessarily XPS, I think he used some ACT prototype equipment).

So flying with XPS close to that station is close to RC-suicide.

regards Peter

P.S. I OWN an XPS/IFS system and are happy with the performance.
But as I'm an engeneer that knows what's possible and being able to recognise HOT AIR when I se it I'm displeased with the deficiencies from XPS.
I'm shure these CAN be solved from the engeneering point it all boils down to JD standing up to his claims and do the RIGHT corrections.

So instead of broadening the system he better FIX the existing one or he may have to cope with a lot of "burnded ground" aka displeased customers that will not buy another XPS, 900Mhz industry changing or not.

[crxmanpat]

Guten Tag Peter,

I for one would gladly review any concrete evidence that XJet, or anyone else for that matter, has regarding XPS equipment not switching channels when a certain noise threshold is reached (not talking about "sudden saturation" here). If that information has been posted in the XPS forum and then deleted, then why has it not been posted in the Radio forum? Jim Drew has no control in that forum.

My guess is that nobody yet has definitive evidence that XPS will not channel hop in the situation Jim describes on the website. And the only thing Jim has admitted to so far is that XPS won't hop in the case of a "sudden saturation" of either the entire band, or the "channel" in use by XPS. But he did say he is working on a fix for that too.

Guys like XJet do pose some valid questions and concerns regarding Jim's claims. But so far I have not seen any hard evidence to back up statements they are making. Jim Drew created and developed this system, so right now I'm "taking his word for it" as creator. That is until someone can prove otherwise.

MfG,

Pat

[vampire67]

Originally Posted by crxmanpat

My guess is that nobody yet has definitive evidence that XPS will not channel hop in the situation Jim describes on the website. And the only thing Jim has admitted to so far is that XPS won't hop in the case of a "sudden saturation" of either the entire band, or the "channel" in use by XPS. But he did say he is working on a fix for that too.

I fully agree.
But this is only for the hopping triggered by a slow increase in the channel noise (This was slowly comitted by JD after being confronted with the "other" proved hopping problem)
There are only doubts fuelled by other XPS claims disapearing like morning fog

However it is also fact that a slow channel noise increase is only valid for stationary RF sources.
If another RF source suddently apeares in the current channels you better have the failsafe adjusted nicely and hope for the best.
For the RC (e..g. 35MHz in germany) frequency this only happens if some bad guy is sitting close to your field to kill planes. The band are usually blocked for general use (except for some lagacy use, e.g. by the frensh)

Ok to be fair the sudden RF source have to be a real mean one.
From what I technically understood usual Wifi and phone stuff use packets.
There is plenty of timeslots even when several stuff is on the same channel.

However 2.4MHz is (or became) a rather busy band. A lot of WiFi, A/V equipment and Phones in the band, not to forget kitchen microwave (as far as I know).
This would be like using 27MHz and having no working automatic "channel hopping".

Peter

[crxmanpat]

Originally Posted by vampire67

I fully agree.
But this is only for the hopping triggered by a slow increase in the channel noise (This was slowly comitted by JD after being confronted with the "other" proved hopping problem)
There are only doubts fuelled by other XPS claims disapearing like morning fog

Peter,

Do you have a link to where Jim stated this? All I have seen him admit so far is that XPS won't hop upon sudden saturation. He still claims that it will hop when the noise level reaches a pre-determined threshold.

MfG,

Pat

[XJet]

Originally Posted by crxmanpat

Guten Tag Peter,

I for one would gladly review any concrete evidence that XJet, or anyone else for that matter, has regarding XPS equipment not switching channels when a certain noise threshold is reached (not talking about "sudden saturation" here). If that information has been posted in the XPS forum and then deleted, then why has it not been posted in the Radio forum? Jim Drew has no control in that forum.

I've already posted my observations (and how they were obtained) elsewhere but realize that a more comprehensive study and analysis is required. That's why I'm currently building some test-gear to provide more insight into this and other issues with XPS and other 2.4GHz sets.

This kind of gear is not readily available "off the shelf" at anything like a reasonable price so I've had to design and build it myself -- not a trivial undertaking.

My guess is that nobody yet has definitive evidence that XPS will not channel hop in the situation Jim describes on the website.

I believe that the description XPS has on its website in respect to frequency hopping may well be true -- but note how *very* carefully it's worded.

No where does it say that XPS will hop when it encounters interference - only when it encounters *POTENTIAL* interference. This subtle distinction on the part of XPS is no accident. Nobody ever gets shot down by potential interference, only *actual* interference.

And the only thing Jim has admitted to so far is that XPS won't hop in the case of a "sudden saturation" of either the entire band, or the "channel" in use by XPS. But he did say he is working on a fix for that too.

If the whole band is saturated (*VERY* unlikely) then hopping is pointless because there's nowhere to hop.

However, when the interference only affects the frequency on which XPS is operating then hopping can save your model (and perhaps a life). This is where Futaba and Spektrum/JR win hands-down right now. Both will continue to operate virtually unaffected if a single chunk of spectrum is clobbered by an interfering signa -- XPS will go into failsafe and your flight is over.

XPS has neither robust agility or redundancy.

Guys like XJet do pose some valid questions and concerns regarding Jim's claims. But so far I have not seen any hard evidence to back up statements they are making. Jim Drew created and developed this system, so right now I'm "taking his word for it" as creator. That is until someone can prove otherwise.

One thing to consider -- what are the motives for my and JD's claims.

I'm system-agnostic. I don't make, sell, promote or endorse any 2.4GHz radio system. I've had good things to say about them all and bad things to say about them all. I simply call a spade a spade. I'd really like to see XPS turned into a robust, cost-effective player in the market - that's good for everyone. I've been strongly critical of XPS and JD solely because I feel that people have a right to get the facts -- not just a bunch of hype and BS.

JD's motives on the other hand are to sell as much XPS gear as he can -- and that's a fair and understandable position. He's running a business and its only natural that he'll try to maximize the return on his investment, I have absolutely no problem with that. However, it is something to keep in mind when interpreting his claims and coments.

When JD talks about antennas that defy the laws of physics and is repeatedly shown to be dead wrong in respect to claims he's previously made regarding the limitations of the system, it should be a reminder that his goal is to sell as many XPS systems as he can. When this conflicts with delivering an honest and truthful appraisal of the system's weaknesses then it's easy to see which road he prefers to take.

All this first-generation 2.4GHz gear has issues, that's to be expected. I'm just trying to provide an objective perspective that sorts the reality from the hype so that folks know what they're actually getting rather than what they're being promised.

XPS has been the worst performer in the hype-stakes. That alone doesn't make it a bad system but it does mean that you believe JD's claims at your own risk.

The sky isn't falling -- but the XPS umbrella does have a few more holes in it than some of its competitors (although perhaps not as many as Futaba's does right now:-)

[vampire67]

Originally Posted by crxmanpat

Do you have a link to where Jim stated this? All I have seen him admit so far is that XPS won't hop upon sudden saturation. He still claims that it will hop when the noise level reaches a pre-determined threshold.

That's what I ment.
But this reply cam AFTER being confronted with proove that it didn't hop on saturation of the channel.

There is not a lot of specific know how in the XPS transmission.
It's based on XbeePro modules (http://www.maxstream.net/)
As this is basically RS232 in/out a small micro doing the Tx sampling and another in the receiver controlling the servos is no rocket science.
(Actually I have seen somewere on RC Groups seen a DIY XPS with these modules INCLUDING working telemetry !)-> http://www.rcgroups.com/forums/showthread.php?t=651255

What makes the system unique were telemetry and channel hopping.
The first is still "Vaporware", the second around 50% proved ineffective.
So what's left

I still hope that the deficiancies can be settled. XPS creditability depends on JD reaction how to settle these "initial" problems.

Peter