I'm not sure on the laws regarding 2.4Ghz in the USA but the smaller wireless video cameras I use are very low powered, way under 1 watt. I have seen some at our field that are 1 watt and we fly Spektrum systems with that thing going with no issues. Its on a glider and the guy flies it with video goggles so he gets a real feeling of being inside the thing. Never has caused a problem so far.

As for the systems having to hop I know thats not the case here. Baby monitors, wireless door phone video etc all use a fixed channel. Some higher end ones allow you to select from three or four channels or on some you have four cameras running and it switches every few seconds. Hopping with smaller cheaper electronics is pretty much unheard of.

However most of these smaller wireless vids do not use up all the band width on the channel. The easy way to explain it is 2.4 has a channel more like a 3D box than a flat line. That box can be seperated up into smaller squares that will theoretically allow up to ten devices to work at peace with each other on the same channel.

Thats how XPS can claim to be able to run 90 radios concurrently. FASST say they can run some enormous number and SPEKTRUM say 40. What ever the number, it really is irrelevant because your not going to get 40 planes or helis in the same airspace with out a lot of control from the CD. Plus I am sure there would be some serious latency as units clashed with each other looking for a gap to send packets of information.

As for XPS claiming to have the only system with Bi Directional capability my understanding is the others have that turned off as they dont want it or need it yet. Sure thing later on you will have your onboard info recorded on your radio and you can download it to your PC at night. Those things are not rocket science to include for either FASST or SPEKTRUM. They just choose not to do it for the time being I am sure.

I have some new software that I hope is going to show the depth or band width usage for each channel. Its pretty technical to make it understandable (for me that is) but if I can get the moons to line up again I will try to do some work tomorrow for you guys and post it.

You know guys something I am not worried about is being proved wrong if anyone can counter what I am doing. This is my hobby, learning by pushing my boundaries of knowledge is rewarding and enjoyable. So dont be shy to fire away if you have proof that shows otherwise. I'm not here for the fight, but I am sure here for the fun.

Originally Posted by cptsnoopy

Thank you Kiwi for responding. I asked the question as it is the very basis of the hopping feature. If the XPS continues to operate normally during your tests then that would invalidate everything you have shown on your video. Since I own quite a few XPS receivers it is still the biggest question in my mind. Will the system hop if it is being interfered with to the point of degrading function if there is a clear (or usable) channel nearby?

Again, thank you for your efforts. They are most definitely pointed in the right direction.

Charlie

Charlie,

The extremely difficult part here for me is to just touch on the point where reception is being lost by the receiver but not enough to put the unit into fail safe.

In my mind if we go to fail safe before we hop a channel then the system just plain does not work. What would be the sense of a system that cannot move before it gets swamped. There was another video on RCG showing the noise levels being slowly increased until XPS chucked in the towel. That was done with a slowly rising noise floor and a rapid rising noise floor. In both cases the Receiver defaulted to fail safe before being able to get out of the noise.

One of the abilties of my signal generator is it can pulse so it creates a variable noise environment that in my mind should be sufficient to make XPS move if it can move at all.

But as I said above. I can be wrong, maybe it does hop but if someone can show us 100% ON A SCANNER or with some device that proves it moves then I stand corrected.

I did a little playing around last night with an X-10 2.4ghz camera that I have had a for a few years. I'm not sure of the power it puts out but they are readily available in the US. With my XDP running in analyzer mode, the camera powered on and sitting about 10 ft from my plane and the Tx about 12 ft from the plane and 6 ft from the camera. The camera showed up at 15 on the XDP analyzer, I then powered up the Rx and Tx and they linked up on 20 right next to the camera. With the Tx antenna removed and NOT pressing the range check button I was getting intermittent control of the Rx (start to move the elevator and it would go part way then stop, then come back to life or go to neutral failsafe setting). So I cycled the power on the XPS Tx and Rx while leaving the wireless camera on, XPS came up on 20 again and was still intermittent. I then moved the camera about 30 ft away and it stopped interfering with the XPS even if I held the Tx right by the camera.

I then brought the camera back near the plane and after another power cycle of the XPS it came up on 60 and then it functioned fine unless I put the camera's antenna right against the Rx antenna. I relinked the XPS about 4 more times and it always came up on 60, even with the camera off, maybe it uses that last channel it had success with??

So, I'm very surprised that XPS linked on a channel that had sufficient noise to prevent it from functioning properly (more than once) AND, I never saw it change channel except when relinked. I may play with this a bit more with a battery pack on the camera so I can vary its distance from the plane.

Looks like I was mistaken about the power levels of the AV transmitters. They are covered under FCC Part 15 until it looks like 100 milliwatts, then FCC Part 97, requiring an amateur license. The Black Widow 200 milliwatt rigs require a Technician Class license. So it would appear (I haven't read all of Part 15 or Part 97, just going off a few snippets here and there) that anything over 100 milliwatts needs a license in the US. The ARRL quotes power levels in microvolts/meter, This video retailer uses microvolts/meter on its Part 15 rigs, milliwatts on its Part 97 rigs. So the guy with the 2 watt Ebay special needs his Ham ticket.

Originally Posted by RichardCorby

I sent an email to XPS tech support to see if there was validity in this set of test results. These negative posts about XPS is causing some problems at the field. People see what I am using and think it is unsafe after reading all the bad press in these forums. So I asked for clarification. Within 12 hours I received this response:

"We have not seen the video. We can't access the flying giants site
apparently.

*Clipped*


And here it is - straight from the horses mouth. Do we fly airplanes or just sit around doing bench tests. For me it's in the flying that proves the system.

Jim Drew still has an account here, and he's not banned. His last activity was from 6/07 I'd like to personally welcome Jim back to this site anytime he'd like to visit.

It was our understanding that Mr. Drew chose to spend his time on another forum due to the difficulty in keeping up with all of the threads in all of the forums.

C'mon back Jim, we'd love to have you!!

He doesn't post much on the other forum these days either.

And here it is - straight from the horses mouth. Do we fly airplanes or just sit around doing bench tests. For me it's in the flying that proves the system

Is this not a little naive?

Do Ford and GM just knock a car together then go drive it rather than putting it through a rigorous set of tests for durability, safety, performance and reliability?

I think not.

REAL WORLD tests clearly show that when a single frequency on 2.4HGz is saturated, the entire band is also saturated.

Unfortunately the promotion of "patented 8-element spherical antennas" and other things clearly indicate that JD's grip on "The Real World" (TM) is tenuous at best.

I also wonder at what constitutes a "test" in JD's world.

When he first rolled out the XPS transmitter modules I posted my concerns that the small quarter-wave whip on the transmitter module would be inadequate, due partly to its low gain and also because of its positioning (wasting most of the power that was radiated anyway -- further reducing the ERP).

JD scoffed and said that he'd done extensive "testing" that proved the 1/4wave whip was all that's needed.

Just a few weeks later (at Vegas), we saw the 1/4wave whip being replaced by a 1/2 wave dipole and now all the transmitter modules sport this "unncessary" enhancement. This is an example of why I question the quality (or even the existence) of JD's "real-world testing".

It does no good to hop when there is clearly no place to hop

To which I must say -- so why is one of the few instances where someone has claimed to actually witness XPS actually hopping when it is in the close proximity of a FASST system? Since FASST is constantly hopping, it makes no sense for XPS to change frequency for "there is clearly no place to hop".

I think JD has become the victim of his own attempts to guerilla-market XPS by making wildly unfounded claims and over-hyping the technology behind it. Making these wild claims certainly got people talking -- and that's good for sales.

Unfortunately, he's now unable to really retract many of those ludicrous claims for fear of being exposed as being somewhat less than totally honest.

So he persists with the mythical antennas, the "useful" hopping capabilities and the denial of any need for receiver/antenna diversity.

Those who have bought his products and had no problems will doubtless support him, others who are not phased by the smoke and mirrors or who have had issues with XPS are not so supportive of this kind of silliness.

I suspect that if the system had not been so grossly over-hyped, we wouldn't be having these discussions right now.

Interestingly enough, there are a growing number of "satisfied users" of non-redundant, non-agile 2.4GHz systems such as ASSAN and iMax who live with even more limitations than those intrinsic to XPS. These people aren't complaining because their expectations were not unreasonably raised and the manufacturers of these systems never made claims that weren't substantiated in practice.

As I've said before -- the XPS system does work and is as good as other second-tier products.

But it is somewhat akin to driving a car without seatbelts or air-bags.

Many of us drove cars without belts or bags back in the 1950s and 1960s without ever suffering an injury. However, now that such safety devices are available, who in their right mind would want to drive a modern car without them? They don't make a difference on a day-to-day basis but on that one day when something unexpected happens, they can save your life.

FASST and Spektrum have the RC equivalent of belts and bags, XPS doesn't. If fly XPS and you're lucky you'll never miss this added safety. If something goes wrong however, you'll sorely miss it.

It's a consumer's choice -- but just as I wouldn't want to be the passenger in a car without belts or bags, I wouldn't want to fly alongside someone using XPS in a large or fast model - just in case.

JD has dug a deep hole for himself and I really can't see a way to climb out. Unfortunately, from what I've seen of JD, I strongly suspect he'll go to the grave denying any deficiencies in his system and boasting things that fly in the face of the laws of physics.

It's a shame really.

Originally Posted by KrisW

After remarks like this from JD, I can see NO reason to even try to give him the benefit of the doubt any more.
Does he think we are stupid??? What an arrogant Ba$&*(#. . .

I agree

My favorite is " We do have to say that our competition is doing a great job of stirring up things. We appreciate the extra attention we are getting."
Yea like FAAST and Spektrum are worried about XPS---Please!!
For a fun time goto RCgroups and read how all the Fanboys are drinking Jim's Kool_Aid....

For a fun time goto RCgroups and read how all the Fanboys are drinking Jim's Kool_Aid

Mr Drew has deleted a lot of stuff he didnt like, theres only a couple who have pledged allegiance to him from the get go still going on about it

I just found this, Mate great job, never knew you had this much talent, you proved that XPS does not hop, anybody can prove otherwise, please post a video, thank you for your efforts mate.

I appreciate the work put into the tests but without actually testing the responsiveness of the system
during the test, I don't see that it proves much of anything. Yes it could not be made to hop,
but what we don't know is if it really *needed* to hop. I assume XPS Tx antenna was on
and it was running at full power during all the tests shown in the video.
If the Rx was still maintaining full control (which we don't know because nobody checked), then there's no reason it would need to hop. Why would we expect it to?
If it was totally blocked by the noise (which we also don't know), then it
would not hop, by design, per admission of JD. And frankly, while JD and apparently Kiwi too
thinks it's a silly idea to hop *after* onset of failsafe, that is frankly the only
case I care about. That's the only time it makes sense to me. "Potential noise" is just
too nebulous and you could easily get yourself in more trouble hopping when it's
not absolutely necessary (still maintaining control but there's more noise than
there was before) than waiting until the link is actually lost long enough
to cause failsafe when you *know* that it can't get any worse.

And as for "first tier" versus "second tier" systems, with the implication that
Spektrum having two frequencies to XPS's one (100% better) makes it first tier is still
a bit short sighted. I watched a Spektrum DX7/AR6100 combo lock out and fall out of
the sky twice the other day in a non-motorized Easy Glider. After our ground testing
with very surprising results, and my subsequent thread in the Radio forum on RCG, I come to learn
that if a Spektrum AR6100 Rx (maybe all models) loses the signal on both channels for any
reason for more than about a second, it goes off into la la land and scans for the Tx
on all 80 channels (assuming that the Tx has been turned off and back on) and may not find it
for another 5, 10, 15 (and in my tests 25 and 40) seconds before it finds it. People are
telling me this is "normal" behavior. And no, we're not talking about the known
low voltage reboot issue, for which there is a fix. We reproduced this behavior on a fully
charged 6V battery pack, on video. All it needs is anything blocking the Rf signal
(range/orientation/shadowing of Rx or Tx) for more than 1 second. At *least* XPS always
hot-links instantly as soon as the Rf signal can get through again. The other model Spektrum
Rxs basically try to avoid this issue by having better diversity (more Rxs and/or more widely
spaced antennas), and that's better, but if the link is lost anyway, then you're still screwed for
that 5-15 seconds while it scans and I don't know of many planes that can survive that long
without control. That's not Tier 1 behavior as far as I'm concerned.

BTW, with regard to 2.4Ghz video transmitters. *Most* people still use 100-200mW.
More people these days are buying 500mW units, and only a small handful of people use
1-2W systems. Anything above 100mW requires a HAM license to use legally. A 500mW video Tx
placed between XPS Tx and Rx will easily swamp the signal if it's on an overlapping "channel". And
contrary to what Kiwi said, the video transmission is fully analog and consumes pretty much 100%
of the bandwidth on its channel 100% of the time.. It may look similar to the rectangular
shaped spectrum of say a Wifi router but it is *not* spread spectrum, it is much higher power
density, it does not play nicely with *anything* close up. If I turn my video Tx on on certain
channels inside the house, it will just kick everything off my Wifi router instantly. In terms of
making XPS upset, a single 2.4Ghz video Tx of sufficient power is a pretty good noise generator
(I've got a bunch of videos showing how I used mine). You can vary the distance between them
to increase and decrease the noise floor gradually.

Anyway, back to the topic at hand.
I still think the "How do these systems actually react to noise" (as in what they actually
do, rather than what the manufacturer claims they do or don't) would be more useful.
Test like this.
1. Increase noise floor on all channels used by the system until onset of failsafe.
How much does it take?
2. Increase noise on all channels used by system gradually while monitoring actual
responsiveness. Do they slow down? Do they get glitchy? Intermittent.. etc
3. Repeat test 1, and then immediately shut off all sources of interference and see how long it
takes before they become responsive again (based on my testing, we'd see XPS come back
instantly, and Spektrum take however long it takes.. 5-15 seconds). After the change that JD is talking about in the software to make it hop after onset of failsafe, that might make XPS take
longer to relink because it has to scan (like Spektrum does now).
4. Introduce noise that is narrower than the SS channel, overlapping that channel, and see how
it reacts. Basically testing the spread spectrum ability of each system. XPS has 12 wide
SS channels so may be more resistant to narrow band interference, than Spektrum for instance.
FASST has very narrow invidividual channels, but it sort of simulates one big fat channel
that covers the whole spectrum. I agree with XJet's assessement of how it'd probably react
to interference. Saturate half the spectrum, it'll run at 50% responsiveness.

We're talking about ability to work through noise to gauge whether the designed in capabilies
are any good. If we discovered that XPS could function normally through twice the level of
noise on its single channel, than Spektrum can on its two channels, would that
level the playing field?

ian

Originally Posted by Daemon

After the change that JD is talking about in the software to make it hop after onset of failsafe

Why, if XPS works perfectly, is JD changing anything ? According to him, he is selling 1000's of units.

Originally Posted by Daemon

We're talking about ability to work through noise to gauge whether the designed in capabilies
are any good. If we discovered that XPS could function normally through twice the level of
noise on its single channel, than Spektrum can on its two channels, would that
level the playing field?

ian

mmmmm. . .no. XPS is not even on the same field, sorry, and I seriously doubt that XPS would work or receive at higher noise levels than Spektrum, especially since Spektrum is on 2 channels at the same time, making the possibility of losing lock a lot less likely. The chance of blocking both Spektrum channels, simultaneously, is so remote as to be laughable. Add in the GUID that enables Spektrum to actually transmit through interference and have a recognizable code train, and things get better looking all the time for the Spektrum units. It would take something blanking out at least 75-80% of BOTH channels, simultaneously, for Spektrum to suffer loss of lock, or degraded performance to the point of difficulty flying.

You have to remember, on such a high frequency, Spektrum is only transmitting for 1/10 of the time, at most. The rest of the time it is monitoring things. At the same time everything else is transmitting in pulse trains as well. . again for about 1/10 of the time, so there are all sorts of big open frequency gaps for the Spektrum pulse train to flow without interference. You are not getting an analog signal from a video transmitter, you are getting pulse trains of information in bursts. I would imagine that the PRF for these data bursts is the same as the screen refresh rate of the monitor, probalby 30 times per second or so, which leaves a lot of open time between these bursts of information for other devices to transmit information. Unless the interference is blanking the frequency totally, at the same time Spektrum is trying to transmit, the signal will probably get through, and being encoded with GUID will be readily accepted by the receiver. Then, to lose lock, you'd have to do it on BOTH frequencies.

The way XPS requires cross talk between the rx and tx means that at any time either unit loses lock with the other, they will try to go into a "find the other unit" behaviour, which can result in both of them going to different channels independently of eachother, then sitting there, making it where the system will NEVER re-link. You will not get that with Spektrum, since the information path is TX-RX, not in both directions.

Please feel free to show us, on a test bench, the Spektrum system taking 5-15 seconds to relink, when it actually takes as little as 1/2 second. The firmware and software changes for Spektrum have removed the long re-link time, and reduced it considerably. It does not take 5-15 seconds to scan every channel that Spektrum uses .. more like 1/2 second given the PRF of the system.

It would make your case a lot more credible if you had some documentation about WHY the AR7000 lost link, twice, in the same aircraft, and could repeat the experience at will with a bench setup.

Personally, I prefer several satellite receivers, with variable orientation of their antennae, to one centralized antenna with an alleged (ahem .. yeah, sure, right, not quite what they say it is) "spherical reception" antenna, which actually has built in null areas at the poles of it's receptivity pattern.

One other little tid bit. . there are several videos showing the XPS system in action, and have a graph showing the interference that XPS sees. When the interference reaches a certain level the XPS goes into failsafe, and does not hop. Over and over the videos show the same things. . interference ramps up, XPS locks out, and never changes channels. Those videos are what killed XPS for me. If it would not hop channels when it got total interference in a testing environment, the chances of it doing it in the "Real World" were pretty small.

I joined just to thank Kiwi for his testing. It is a nice change to read objective posts from people with open minds.

I'm looking forward to the other tests and this is where I will send people who are trying to decide which 2.4 system to buy.

Thanks again Kiwi, and keep up the good work .

Hi all first post,so a big hello from north carolina.

Well ive been watching these threads from all the forums,and ill just say that im flabbergasted by the amount of people who have stuck their heads in the sand over this issue.
First and foremost,all of the 2.4's have had growing pains,pretty much any new electronic system does.Be it buggy software or bad layouts or poor implementation,everything will go through some form of growing pains.The hallmark of a good company will be how it implements a fix,ie..futaba doing a recall and setting up testing centers,spektrum upgrading for free anyones rx to the newer firmware and fast reconnects.These are traits that are desired of any company that wants to gain or keep my business.All I have seen from XPS and JD is denial that they have any sort of problems.I cant count how many owners I have seen berated for having supposed poor setups that caused their crash( never XPS's fault)
I would love to know the exact post count that JD has deleted from folks that said anything bad about his baby.And it is totally laughable that anyone who is as system savvy as JD claims to be would even dare to say that true bench testing is worthless.

On Kiwi's vid I could see futabas faast hopping like a bunny.Ive seen the twin signals from spektrum,that they never ever have claimed can hop just sit there and do their 2.4 thing.The only system that has not done what it has claimed it can do is XPS.
The best ones are the replies of "well mine has worked great for 2 years "so your full of beans.Well i am glad that XPS has worked for these folks,and I truly hope it continues to,buuut(theres always a but)if you do get locked out and your new whizbang 4banger retractable gear biplane decides to eat dirt,I hope that you l remember all these tests when your told that you elevator servo was not aligned with jupiter and the rings of saturn and its all your fault.

And last,to Daemon concerning the DX7/6100 in the glider.Please inform your friend that the 6100 is classified from spektrum as a parkflier rx and as such,is not suitable for a glider.Tell them to get a 6200 rx as it is a full range rx with the needed satellite rx.

Kiwi your tests are great and I cant wait to see them all finished and posted.
see Y'all later
john