Independent tests prove lack of frequency hopping with XPS

[buttface]

	Quote: Originally Posted by Daemon
	On a side note, JD and others familiar with the Xbee modules have stated that the Rx drives the whole channel selection process. It's not looking for the Tx at all. It scans for a channel with a low noise floor at startup and then sits there transmitting "Hi, I'm on channel X bound to Tx Y, come find me". When Tx Y is turned on, it just scans through all the channels looking for the Rx sending the message that matches its GUID (really the MAC of the Xbee module). If you turn the Tx on before the Rx, then the Tx just goes into perpetual search mode, until the Rx is turned on, does it's own channel scan, selects a free channel and starts broadcasting its message. Could be interesting to see what happens on the spectrum when you turn the XPS Tx on without the Rx. Do you see it transmit at all? ian

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50% of the time my XPS would not connect upon turning it on and I would have to turn it off and back on again. Why dose that happen?When you turn on the FASST "ITS ON!" (pun unintended) lol

[Flatlandman]

Kiwi, why did you not turn on a futaba fassst system to see the results or any other system. The one confirmation to the hop supposedly came from the fasst system. Theres to much assuming in these tests (all of them not pointing at Kiwi's test on this); I read to many statements like "that should do it" almost like they're trying to be right and not so much get it right. I just want to see some info that proves it doesn't hop and what we're getting so far is it doesn't hop in these 3 situations. For me this myth isn't busted just yet although I'm still very very concerned.

[buttface]

I think all XPS equipment should be grounded by the AMA until it has been proven safe.

[wrightme]

This looks like the XPS did not even attempt to hop with this setup. To add to the data, did you also see what the status of the link state was?
i.e., did the TX/RX remain linked, decrease control sensitivity, or lock-out going in to failsafe, or cease responding without entering failsafe?


Nice spectrum analyzer equipment it looks like.

Also, it is worth noting that the FASST antenna touch MIGHT have caused a lasting problem with the RX in that "supposed induced hop" test. (if I read the information correctly).

	Quote: Originally Posted by Kiwi
	Well that about does me on XPS folks. I will not say it does not hop channels as there may be a way that it can. But so far I have: Raised the noise floor slowly Pulsed on the same channel Drowned it with interference And none of those scenarios causes XPS to swap to a cleaner channel. SO what's my verdict. If XPS hops channels then please someone show us on this site and in this thread how, why when and where because I cannot force it to do so, no one else has been successful in doing so. I'm buggered if I know how. I'm out of ideas and scenarios. I personally would not use this system until its proven. XPS cannot be made to HOP under reasonable test conditions and circumstances that should force a frequency change. So after all that I turned off the sig gen and yes sir. XPS was still happily firing away on channel 11. No thank you.

Edit: Question. Do you have the firmware versions for the units under test? May not make a difference, but doesn't hurt to know.

[bgold]

Kiwi: Did or will the the radio continue to work during your tests and if it fails or goes to failsafe at what level does that occur and is it same or different under the different tests you performed. Thanks
Bill

[sweetpea]

	Quote: Originally Posted by buttface
	I think all XPS equipment should be grounded by the AMA until it has been proven safe.

Then ASSAN and several other one freq brands of 2.4 need to be banned as well.

[Kiwi]

Guys.

I wont have the FASST equipment here until mid next week. It has been the hardest to pin down. The Spektrum system I should have here with me on Monday.

As for the XPS going into fail safe it does if I swamp it but it does not if I run the noise floor up all around it, pulse it etc. Hitting it hard front on does knock it over.

My thoughts on why it is doing that dont matter. My thoughts were that XPS would move away from that steadily rising noise floor even if it does not knock the system over. I thought it would look for a cleaner environment if the situation got murky for it.

Also their was ample evidence that XPS slowed down and sometimes did not respond instantly to a control input when those pulses and traverse tests were being done. I dont have any way to see how many packets were lost or what the delays were in real time. But the system got slow and jerky.

Guys I need to take some time out as work requires that I'm away for the next 6 days. One thing I want to do is set the receiver up for a shorter fail-safe reaction and I want to change the power settings on the Tx. I also want to space the Rx much further away from the Tx as they are sise by side at present and thats not a real world situation.

As for turning all the systems on together and letting them have a free for all that wont show anything. FASST, XPS and SPEKTRUM and ASSAN will all live harmoniously together with just three or four, our ten or twelve radios all working. I will try to do that but I only have one module based FUTABA radio and that runs ASSAN, FASST and XPS for me. Its kinda hard to plug all three modules in at the same time.

However guys the point of the initial test was to make XPS hop. Not to see if it went into fail-safe or see if it stood up to the test of being slammed with interference. My test was to find a way to make it hop first. Actually the whole reason for the thread in the first place.

With what I done XPS will not hop. I dont have any other devices at my disposal to clinically make it do so. If it hops in the presence of FASST then we will see it as I will test it as promised.

All the systems I have will get the same battery of tests I carried out with XPS. This is not over, its not aimed at exposing XPS as being anything its not. Hopefully it is just pure plain old facts ungarnished with opinion.

[jonkoppisch]

	Quote: Originally Posted by JimDrew
	Wires moving around the receiver is a potential cause. We have had many reports of a snap roll or other high-G manuevers inducing a failsafe condition. If servo leads are allowed to move back and forth around the receiver, this changes antenna frequency and the system can no longer "hear". Simply securing the wires in every reported case solved the issue.........

Wiring seems to be a popular excuse for loss of signal. That should be included on the next round of tests.... Seems that if the receiver is that vulnerable to wiring then the case design seems rather poor?

[jonkoppisch]

	Quote: Originally Posted by sweetpea
	Then ASSAN and several other one freq brands of 2.4 need to be banned as well.

I thought assan was for park fliers? If so, they have rated it correctly instead of making up magical spherical radiation antennae systems...

[ricoalonso]

In another thread at RCG where someone claimed or thought that they were able to make XPS hops to another channel using FASST system to emulate the noise, it don't think they experienced the XPS to lockout. What I remember is that he mentioned that there were some glitching experienced in the servos. To me, it means that XPS doesn't really have to go to lockout state before hopping, which makes sense because if the Rx can no longer communicate then it cannot tell the Tx to change frequency. So, I would think that as long as the noise is brought to a level that some packets get lost but before lockout then XPS should have 'hop' already... that is if it is really capable of doing so.

[buttface]

	Quote: Originally Posted by jonkoppisch
	I thought assan was for park fliers? If so, they have rated it correctly instead of making up magical spherical radiation antennae systems...

You can see the spherical radiation waves traveling though the air if you are wearing X-Ray vision glasses!But only if the Flux Capacitor doesn't have a broken pig tail.

[Julez]

Hi!

What sense would it make trying to hop away from an FHSS signal?
This would be like walking around on a football field trying to stay dry in the rain.

It is the eave that must be avoided.

[wrightme]

	Quote: Originally Posted by sweetpea
	Then ASSAN and several other one freq brands of 2.4 need to be banned as well.

A walk down THAT road leads to banning of ALL single channel systems! 72mhz is one radio per channel at a field, PERIOD. At least the XPS can coexist with another tx/rx set on the same channel. (Note: Do not misconstrue this, I do see the failure to hop in this test.)

[sweetpea]

	Quote: Originally Posted by wrightme
	A walk down THAT road leads to banning of ALL single channel systems! 72mhz is one radio per channel at a field, PERIOD. At least the XPS can coexist with another tx/rx set on the same channel. (Note: Do not misconstrue this, I do see the failure to hop in this test.)

That was my point. XPS was no more dangerous than any other single freq system. (now it may not be more optimum in some situations than other single freq systems but that is another point)

If the hop algorithm is truly non-exstint or non-practical than the wording in the package needs to change and maybe it shouldbe reccommended not to be used by GS/Jets.

But that will always be up to the individual flyer.

[bosshoss]

This is a great thread, the continuing pursuit of better control of our models....

Kudos, KIWI, Xjet......emotions set aside, the info is great and informative, let's hope the developers in our hobby are watching closely. Scrutiny drives perfection.