Kiwi's XPS test results are up.

[Julez]

No, unless the RF power is strong enough to effectively block your current channel.
This seems seldom to be the case, but it seems to happen every once in a while nonetheless.

[easytiger]

	Quote: Originally Posted by Julez
	No, unless the RF power is strong enough to effectively block your current channel. This seems seldom to be the case, but it seems to happen every once in a while nonetheless.

What you mean is yes, unless your transmitter is stronger and or closer to your receiver than the interfering transmitter.
Being that there are literally millions of devices that are perfectly legal to use the same frequency you are using for XPS, it suddenly becomes LIKELY that you will be shot down, sooner or later.

[ss40]

	Quote: Originally Posted by easytiger
	What you mean is yes, unless your transmitter is stronger and or closer to your receiver than the interfering transmitter. Being that there are literally millions of devices that are perfectly legal to use the same frequency you are using for XPS, it suddenly becomes LIKELY that you will be shot down, sooner or later.

\

He said what he meant! What part of no you will not get shot down do you not understand?, unless you are swamped on the frequency which is EXTREMELY unlikely.
Lots of TX's on the same frequency can co-exist. You have completely revealed your total lack of understanding here.

[Simpleton]

	Quote: Originally Posted by easytiger
	RCgroups took his money, and are complicit in this whole thing. They can't feign ignorance, the owners knew Jim's past history, they were just "lucky" enough to get Jim's teeny advertising budget, and dishonest enough to be willing to be a partner in this unholy mess. They deserve whatever long-term loss of credibility they get from all this.

This is a bit puzzling, as they seem to be otherwise pretty good at keeping the undesirable riff-raff out.

[easytiger]

	Quote: Originally Posted by ss40
	He said what he meant! What part of no you will not get shot down do you not understand?, unless you are swamped on the frequency which is EXTREMELY unlikely. Lots of TX's on the same frequency can co-exist. You have completely revealed your total lack of understanding here.

Nope. You'll get shot down. Which is continuing to happen with XPS.

Ahhh, the Fanboys. Gotta love them. "What you don't understand is that the Sperical Radiation Technology causes an excitation of the negative aerion particles making XPS completely immune to interference, EVEN IF YOU ARE FLYING YOUR AIRPLANE UNDER A KITCHEN SINK. All you doubters are just working for Futaba and lack the technical understanding to even skim the SURFACE of the genius of a freindly alien like Jim Drew, who comes from a society so technologically advanced that the very laws of physics can be bent, warped, rechanneled, and alinged at will using just a mere fraction of Jim's mentallic powers!"

You guys got hornswoggled by a huckster. A guy who lies fairly fluently, and rather consistently. Deal with it.

Prove to me the veracity of Jim Drew. Show me where he went to college. He said he got three degrees from the U of Oregon, Klamath Falls. He did not. So...did he go to college at all?

Anyway...while this is all fun, it's kind of a sick joke at this point. It's all fun and games until somebody loses an eye, or crashes a triple-engined turbine onto a highway.

No matter how you slice it, it's still baloney.

[Flyfast1]

	Quote: Originally Posted by easytiger
	Nope. You'll get shot down. Which is continuing to happen with XPS. Ahhh, the Fanboys. Gotta love them. "What you don't understand is that the Sperical Radiation Technology causes an excitation of the negative aerion particles making XPS completely immune to interference, EVEN IF YOU ARE FLYING YOUR AIRPLANE UNDER A KITCHEN SINK. All you doubters are just working for Futaba and lack the technical understanding to even skim the SURFACE of the genius of a freindly alien like Jim Drew, who comes from a society so technologically advanced that the very laws of physics can be bent, warped, rechanneled, and alinged at will using just a mere fraction of Jim's mentallic powers!" You guys got hornswoggled by a huckster. A guy who lies fairly fluently, and rather consistently. Deal with it. Prove to me the veracity of Jim Drew. Show me where he went to college. He said he got three degrees from the U of Oregon, Klamath Falls. He did not. So...did he go to college at all? Anyway...while this is all fun, it's kind of a sick joke at this point. It's all fun and games until somebody loses an eye, or crashes a triple-engined turbine onto a highway. No matter how you slice it, it's still baloney.

Doesn't the binding provide some protection against other users? I have personally seen and used XPS with multiple other 2.4GHz radios operating at the same time (XPS, Spektrum, FAAST) and they appear to coexist just fine. I think even the XPS system frees the user from frequency pins.

-Ed B.

[easytiger]

	Quote: Originally Posted by Flyfast1
	Doesn't the binding provide some protection against other users? I have personally seen and used XPS with multiple other 2.4GHz radios operating at the same time (XPS, Spektrum, FAAST) and they appear to coexist just fine. I think even the XPS system frees the user from frequency pins. -Ed B.

Some protection from the binding, yes. And, yes, it frees you from frequency pins. But Spektrum uses two channels, so if one gets swamped, the other still works, and FAAST is continuously hopping. XPS has a serious built-in flaw.
I am sure you are indeed flying it, and have had no problems yet, but you are playing with fire. Too many people have the same story...it works great, for a short time, or for a long time, then BAM!
And there seem to be other problems, too, software bugs and the like.
Watch out...the XPS fanboys, many of whom are paid shills, will just deny any problem, and explain it away with long-winded explanations that don't actually hold water under scrutiny. Never a straight answer...and...it's NEVER XPS's fault. Never. Never.

[XJet]

The question "what does it take to shoot down a 2.4GHz system" is a good one and is something for which there are many conflicting claims.

JD claims that any signal which is strong enough to affect his XPS system (on its chosen channel) will have saturated the entire band and therefore hopping in such situations is a waste of time.

If that is the case (which it isn't) then one would have to ask why he even bothers to do a noise-check and select the system's operating frequency based on the results of that check.

Surely (based on what he's saying) he could just pre-configure XPS systems to operate on a *fixed* channel. After all, if there's interference strong enough to affect XPS, it must have obliterated the entire band anyway so *all* channels will be unusable.

Of course this is utter BS and it's very common for *parts* of the 2.4GHz band to show extremely high noise levels while other parts (just a few 10s of MHz away are virtually silent.

So what happens when the channel you're on is also used by another system/service?

Well with DSSS, the background noise increases.

Under "ideal" conditions this isn't an issue until the noise level increases to the point where you begin losing a significant number of data packets. This requires a significant intensity of signal both on the spectral and temporal lines.

DSSS is a bit like whackamole -- each transmitter "pops up" on a spot frequency within the operating channel seemingly at random and since there are many "holes", the chances of two moles (transmitters) attempting to pop up through the same hole at exactly the same time are very remote. Since the receiver is only looking at one hole at a time (based on the spreading code used), the moles that pop up in adjacent holes (ie: other transmitters) are effectively ignored because, although they're on the same channel, they're not using exactly the same frequency at exactly the same time).

Now as you add more and more systems to the same channel, the mole-collisions become more common so some of the data gets lost (two moles can't pop up through the same hole at the same time). An analogy of this might be the way that a weak radio signal dissolves into background hiss when the signal fades -- the noise overwhelms the signal.

So our DSSS systems are very resilient to other interfering DSSS transmissions on the same channel.

However, "constant carrier broadband" transmissions such as video transmitters are another kettle of fish. They effectively plug all the mole-holes with their "always on" signal that spreads right across the operating channel. If the signal is strong enough, none of the moles sent by *your* transmitter can get through the holes and data is lost.

You'll also recall that earlier on I talked about an "ideal world"... well we don't fly in an ideal world so this introduces another problem.

Because our aircraft are constantly changing direction from and orientation to our transmitters, the strength of the signal they see varies dramatically -- by a factor of up to several tens or hundreds of thousand.

This is one of the reasons why antenna diversity is so important on a receiver (a weakness in the case of XPS). If our signal is very weak (because the model is at an unfavorable attitude/distance) then an interfering signal that was previously having no effect may well become many hundreds of thousands of times stronger than the signal from our own transmitter. In that case, its moles may well appear so large that they start squeezing out of the hole in which we expect to see our mole. Or a mole that was previously too small to compete with our mole is now much larger than ours so *it* gets to use the hole and ours is unable to get through.

That means we can experience a momentary (or perhaps longer) lock-out even though the rest of the flight was uneventful.

What we need to do now is quantify the magnitude and density of any signal required to significantly degrade the operation of the current crop of 2.4GHz RC systems and translate that into some kind of meaningful real-world metric.

Since my testbed is now all set up, I'll be attempting to do this in the coming weeks.

Once this is done, I'll be calibrating the alarms on my spetrum analyzer to warn when these limits are being approached for any of the gear I test. This might be a useful asset to anyone contemplating flying from a field with a hostile 2.4GHz environment.

Stay tuned (so to speak)... more to come.

[wrightme]

	Quote: Originally Posted by easytiger
	Some protection from the binding, yes. And, yes, it frees you from frequency pins. But Spektrum uses two channels, so if one gets swamped, the other still works, and FAAST is continuously hopping. XPS has a serious built-in flaw. I am sure you are indeed flying it, and have had no problems yet, but you are playing with fire. Too many people have the same story...it works great, for a short time, or for a long time, then BAM! And there seem to be other problems, too, software bugs and the like. Watch out...the XPS fanboys, many of whom are paid shills, will just deny any problem, and explain it away with long-winded explanations that don't actually hold water under scrutiny. Never a straight answer...and...it's NEVER XPS's fault. Never. Never.

Really? Who might those be? What do you base this upon?

[XJet]

	Quote: Originally Posted by easytiger
	Watch out...the XPS fanboys, many of whom are paid shills, will just deny any problem, and explain it away with long-winded explanations that don't actually hold water under scrutiny. Never a straight answer

On that basis, perhaps JD ought to run for president :-)

[wrightme]

	Quote: Originally Posted by Reckless Loony
	The CH parameter range is 0C to 17 hexadecimal which in decimal is 12 to 23. To understand the hexadecimal base 16 number system http://en.wikipedia.org/wiki/Hexadecimal Anyway the frequencies the Xbeepro 2.4Ghz operate on is given by Centre frequency = 2.405Ghz + (CH – 11) x 5Mhz Thus 2.405Ghz + (12 – 11) x 5Mhz = 2.41Ghz 2.405Ghz + (13 – 11) x 5Mhz = 2.415Ghz 2.405Ghz + (14 – 11) x 5Mhz = 2.42Ghz and so on till 2.405Ghz + (23 – 11) x 5Mhz = 2.465Ghz These are the only frequencies the Xbeepro RF modules can be switched too. Thus for the lowest frequency of 2.41Ghz if we now apply the JD BS of looking for noise 15Mhz away then 2.41Ghz – 15Mhz = 2.395Ghz which is outside the 2.4Ghz ISM band and further more on a frequency that the Xbeepro RF module can’t change too because the lowest frequency that the modules can be switched to is 2.41Ghz. .

Cool. I am sure that those here who are not familiar with hex will appreciate the information.

Now as to the claim you are attempting to debunk. So you have found ONE instance where the signal will not be 15mhz away? So what? JD never said that the system looks for signals AT 15mhz +-. He clearly stated WITHIN +-15mhz. In the case you present, his statement means that it will look within that range, not beyond it. In the specific case, if it doesn't look outside of the ISM band, or if it DOES look outside the ISM band has no relevance. Why do you seem to feel that it does? The module doesn't have to be able to move to the 4.395 frequency to fit the description of action that JD presents. Where do you see a failure in his statement?

[KrisW]

	Quote: Originally Posted by easytiger
	Nope. You'll get shot down. Which is continuing to happen with XPS. Ahhh, the Fanboys. Gotta love them. "What you don't understand is that the Sperical Radiation Technology causes an excitation of the negative aerion particles making XPS completely immune to interference, EVEN IF YOU ARE FLYING YOUR AIRPLANE UNDER A KITCHEN SINK. All you doubters are just working for Futaba and lack the technical understanding to even skim the SURFACE of the genius of a freindly alien like Jim Drew, who comes from a society so technologically advanced that the very laws of physics can be bent, warped, rechanneled, and alinged at will using just a mere fraction of Jim's mentallic powers!" You guys got hornswoggled by a huckster. A guy who lies fairly fluently, and rather consistently. Deal with it. Prove to me the veracity of Jim Drew. Show me where he went to college. He said he got three degrees from the U of Oregon, Klamath Falls. He did not. So...did he go to college at all? Anyway...while this is all fun, it's kind of a sick joke at this point. It's all fun and games until somebody loses an eye, or crashes a triple-engined turbine onto a highway. No matter how you slice it, it's still baloney.

Easytiger. . perhaps you need to get off the methamphetamines and energy drinks. . calm down, BREATHE .. take a nap (or 5). . have a couple of beers, and RELAX!!! You are making me tired with your constant accusations, vitriolic statements, accusations, assumptions, and carrying on in general. It's really painful to read all the hate festering anger in your posts. . .

So. . please. . lighten up a git and relax. . the world is not going to end simply because JD is in business.

If you hate him that much, go pay him a visit and have a nice heart to heart chat with him. I'm sure he would appreciate your candor and honesty. . . .

[seattle_helo]

Sorry to take this a bit off topic, but could someone please explain to me how the XPS system chooses what frequency to operate on upon power up? Is it at all similar to Spektrum where an initial scan takes place to survey the spectrum before choosing its channels? If this has already been pointed out somewhere else, my apologies- it's hard to find things in these XPS threads. Many thanks!

[XJet]

	Quote: Originally Posted by seattle_helo
	Sorry to take this a bit off topic, but could someone please explain to me how the XPS system chooses what frequency to operate on upon power up? Is it at all similar to Spektrum where an initial scan takes place to survey the spectrum before choosing its channels?

Yep, that's the way it's supposed to work although testing seems to indicate that it sometimes gets it wrong.

I've seen it start up right in the middle of a band of frequencies that were saturated by a video-transmitter but the next time it was power-cycled it chose a different operating channel.

By and large however, it's a strategy that seems to work well enough.

[seattle_helo]

Okay, I see.

Well, in the back of my mind a selfish concern I have is that someone with an XPS system could potentially harm a pilot using Spektrum if in fact it choose to operate near or on one of the channels occupied by the Spektrum transmitter. I've read quite a bit about how both Spektrum and FASST operate and interact, but I'm not as familiar with how XPS plays with others. I'd hate to have 50% of a Spektrum RF link compromised by another RC unit. That would be very unfortunate.

nick