Kiwi's XPS test results are up.

[KrisW]

	Quote: 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.

[Chris F]

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 .

[aristo1963]

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

[Daemon]

	Quote: Originally Posted by Pale Rider
	Why, if XPS works perfectly, is JD changing anything ? According to him, he is selling 1000's of units.

"To appease the masses", he might say. I'm not a cheerleader for JD.
Most of his premises are faulty. Even the one about "this change is only for those people
who might turn an onboard video Tx on after the plane is in the air" is BS.
I fly FPV and am active in the FPV community, and almost nobody who uses their video system
that way. No point in turning the video on and off in the air. . And even if XPS can hop
away from the video's very wide channel, the noise floor is still going
to be so high with the Tx physically so close, that the range would be severely reduced.
Nobody in the FPV community is currently running 2.4Ghz RC control with 2.4Ghz video
successfully regardless of which system they use. If the video Tx doesn't cut the effective
range down to about 1/10th maximum, the RC Tx so near the video Rx on the ground
causes constant visible noise. If people fly with 2.4Ghz RC control, they use 900Mhz video.

With my 500mW 2.4Ghz video gear I can easily tromp on an XPS signal at close range
*and* by actually watching the wireless video transmission, I can see when XPS Tx is
transmitting (visible noise on the video picture) and retransmitting (lots of noise on the picture),
and if it hops (which I haven't seen it do yet), the noise goes away. I've verified that,
by turning the video Tx on first, then XPS and can see that I have control (where I
did not, before while it was on the same channel) and see no visible noise. With the
updated code JD is talking about, it'll be interesting to see how fast it reacts.

The type of noise I'm interested in is external and of undetermined origin. I'm not worried
about WiFi routers (for the most part) or other RC systems. But the type of noise
that shot down a fellow local flier using Spektrum gear, as mentioned above, twice
in one day.

ian

[Daemon]

You seem to be under some misconceptions about what technologies XPS uses
and how they work, as well as what Spektrum does for that matter. Some of
them fairly common, some of them you really should know better. Hopefully I can clear them up.

	Quote: Originally Posted by KrisW
	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.

Except I've witnessed it in the air, from an unknown noise source.
I could probably do it with one or two of my 2.4Ghz video Tx's fairly easily.

	Quote:
	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.

Every RC 2.4Ghz SS system uses a GUID, including Spektrum, XPS, FASST, Assan, and
whatever Airtronics is calling theirs. This is inherent in spread spectrum
transmissions for RC use, and gives no inherent advantage to Spektrum over the others.

	Quote:
	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.

Again, this is inherent to any current RC SS system, because we're only transmitting about
5Khz worth of data, spread over at least 1Mhz of potential bandwidth, so it can be sent in very
short packets. All of the 2.4Ghz RC systems use only a fraction of the time on channel,
including Spektrum, XPS, etc.. Again, no advantage to Spektrum.

	Quote:
	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,

Video transmissions are analog, and continuous. When the scan gets to the bottom
of the sensor it starts again at the top. There's no pause in the transmission between
frames except for the blanking interval, but being an analog signal that is transmitted too
(it's just not as information rich as the rest of the frame), but it's still information on
the frequency all the time.

	Quote:
	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.

Even if their were a lot of open time in the video transmission, this gives Spektrum no
advantage over any other 2.4Ghz SS RC system, including XPS. Spektrum, XPS and Assan
use packet based DSSS technology, and only transmit about 1/10th of the time on channel.
XPS can retransmit if its 1/10th collides with someone else's 1/10th, or 5/10ths or whatever.

	Quote:
	Then, to lose lock, you'd have to do it on BOTH frequencies.

It happens. I've now seen it happen twice, in the air.

	Quote:
	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" behavior, which can result in both of them going to different channels independently of each other, 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.

This is false. XPS does not currently go into a search mode when it loses the signal. EVER.
Kiwi's tests and my own have shown that XPS never hops in response to overwhelming noise.
Even JD has admitted that it never hops in response to noise that would block the link
and drive it to failsafe. He claims he's changing that behavior now.
Normally the XPS Tx sends a packet, and expects an ACK from the Rx. If it does not receive an ACK
within a very short timeframe it sends the packet again, and again. It can retransmit
up to 3 times before the next PPM frame (that's 3 times within 20 ms) at which time it just
updates the packet with data for the next frame, sends it and continues on. If the Rx can hear
the packets it responds to them normally by updating the position of the channels and sending an
ACK back. It doesn't hurt it to respond to both the original and a dup packet (if Rx can hear Tx
but Tx can't hear Rx), because no positional information changes between PPM frames.
My own tests have shown that when the noise (or whatever is
blocking the signal) goes away XPS re-links instantly, because the Tx is re-transmitting
continuously on the original channel (same one the Rx is listening on). I've got videos
of that, if you don't believe me. Even if the Tx is turned off (for any length of time) and turned
back on, it relinks instantly by checking to see if the Rx is listening on the last used frequency.
Same for the Rx. Only time it goes and finds a new channel is if you turn the Rx on, and it
can't immediately hear the Tx. Then it goes and finds a new channel and waits for the Tx to
come get it. Power cycle yes, loss of link, no.

And the irony of your statement about XPS getting lost while the link is gone, is that that
is exactly what Spektrum does, by design. If the link is lost (both channels
blocked for whatever reason) for some amount of time (seems to be around 1-2 seconds)
then Spektrum Rx assumes that you've turned off the Tx and turned it back on
(at which time Tx would find a couple of new low noise channels to listen on), so the
Spektrum Rx goes off looking for the Tx across all 80 channels. If the Tx has not been
power cycled and is still transmitting on the original two channels, then the Rx could be busy
scanning even long after the reason for the original loss of link is gone,
and the signal from the Tx could be heard, if the Rx were listening.
The reason for this behavior is because it is a one way link. The Rx can't tell the
difference between a normal power cycle of the Tx (which will usually cause
the Tx to pick 2 new channels) and a loss of link for any other reason. If it can't
hear the Tx for some amount of time on the old channels, it *must* go scanning for it,
or it'd never find the Tx in the first place.

	Quote:
	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.

Easier just to direct you to the thread I started a couple days ago.
http://www.rcgroups.com/forums/showthread.php?t=830928
I've posted videos there of our full power range test and low power (range check button pressed)
tests. We were causing the loss of link by blocking the signal with my body
(water attenuates 2.4Ghz very well) and then re-exposing the Rx to
the Tx's signal, by which time it was too late, and it was already off scanning.
It went off scanning for 20 seconds in one video, and 40 seconds in the other.
What's more interesting than my video'd tests though, is all the various people (including
many longtime Spektrum supporters) saying "Oh yes, some delay is normal, I've seen it
take.. X seconds" where X is 5, or 11, or 15 seconds. Even if my friend's AR6100 is defective
and the 20 and 40 second relinks are abnormal, regular Spektrum users are telling me that
5-10-15 seconds *is* normal. My test is *very* easy for anyone to try to reproduce,
but you have to actually block the signal for more than a second or two before the Rx
goes scanning. Spektrum will hot-re-link very quickly, if the signal is lost
for less than a second.

	Quote:
	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.

Actually, the stated reason from Spektrum for the firmware update is only to fix the low power
reboot/relink time, not to address relink after simple loss of signal. In the earlier firmware
versions of the Rx, if power was lost even for a moment (brownout), it'd reboot and start
scanning immediately, which could take 5+ seconds or so. With the update, it keeps track of
the last two channels used and tries them first after it reboots, thus doing a hot re-link in less than
a second if possible. I understand the different. I'm just not sure that you did. Now it
*is* possible that they've done more with the firmware update than they've admitted, and I'm
still waiting for someone in that thread to prove to me that a new firmware version of the Rx
will not exhibit the slow relink after loss of signal. I'd also like to see someone test on a
different model Rx than the AR6100. With a faster processor or Rf board or whatever,
it might be able to scan quicker. As I said the test is easy but it's gotta be done correctly
to prove anything.

	Quote:
	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.

I did say I had video, and I did say there was a thread on RCG didn't I? You could have gone
and checked, before you intimated that I was lying, but whatever. The proof is there.
The experience of others is there. I knew the moment I saw it happen in the field, that
someone would say "That's impossible. You're full of it. Where's the video?" So we made
a video. And predicting that as soon as I posted the first video, someone would say "It's a
power problem" we ran the second test with a fully charged 5 cell 6V battery pack *with*
an onboard voltage tester to verify that it was not just rebooting due to low voltage.
It's easy. Full loss of link for 2 seconds, it goes scanning for 5+ seconds.

	Quote:
	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.

So do I. I don't believe XPS is bending the laws of physics any more than you do.
I pestered JD about the lack of physical diversity and remote receivers and such a LONG
time ago, the first time I tried putting an XPS receiver inside a 100% carbon plane, and it
cut my full power range down to effectively ZERO. With a side plug Rx and
a single quarter wave whip antenna, there's just no way to get the antenna outside
the fuse, and it'll always be shadowed by the fuse or wing or whatever at
some orientations. Turns out, since then I've seen people try *very* hard to get
other 2.4Ghz systems to work in 100% carbon planes (including one guy using
a Spektrum Rx with two remote receivers with antennas poking out of his fuse
in 4 places. It range checked ok, and then almost immediately started to lock up
in the air and fall out of the sky. He just barely got it back on the ground in one piece.
End of experiment. Others have tried with other 2.4Ghz systems with similar results. I
don't trust 2.4Ghz RC systems around 100% carbon planes any more, at all. None of
them.

But, let's talk about the diversity issue a bit more. Other than shadowing, one of the biggest
reasons for having physical diversity with 2.4Ghz is to avoid multi-path interference where a reflection of the signal arrives at one antenna a half wave off from the original signal and nulls
it out. XPS does not have physical diversity, but it does have what could best be described
as temporal diversity. Because it can and does retransmit lost packets, a single antenna
has 3 or 4 opportunities to hear the same packet between PPM frames, and since the plane
is moving, those opportunities all occur in different physical locations. So for instance with
Spektrum you might have two antennas separated by 10 cm and only hear the signal on one
of them, due to multipath interference on the other. XPS's single Rx antenna may fail to hear
the signal when it's at the same location as the first Spektrum antenna, but after its moved
10cm it hears the retransmitted packet at the second location. That's the trick
that a two way link provides. Retransmits + motion allows temporal diversity to
perform the same job as physical diversity. It's not inherently better or worse. It's just
different and provides equivalent protection for that particular problem.
It doesn't solve the problem of nulls or shadowing though. Unfortunately
systems that have a two way link have problems if you try to transmit on two closely
spaced antennas. You actually *create* multi-path interference right at the
transmission source, which is probably why the XBeePro hardware
that XPS is based on, doesn't do that, and probably never will.

	Quote:
	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.

Yes, you're right. It does not currently hop when it experiences total blockage of the signal
due to noise. I have videos showing that myself, posted in a different thread on RCG Radio
forum (search for "zombie state"). Ironic because you claimed that it'd go off and get
lost trying to find a new channel near top of your post.
But like you, I think this is the one case where it'd sure be nice if it did hop. Although I don't want
it to take 5-15 seconds either. A normal cold boot of XPS (initial scan and link, usually
only takes about 3 seconds though), so it should never take longer than that. It's only
got 12 channels to scan.

ian

[Daemon]

	Quote: Originally Posted by aristo1963
	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.

That's fine, but we are talking a simple Elapor foam glider (nothing to block the signal) that's
flying no further away than you'd fly a park flier around a park. In some ways slopes are
more confining since the lift band is narrow and only out in one direction. He didn't fly it out
of range. What I know he'd like to see now (as would I) is proof that the higher model Spektrum
Rxs if confronted with the same loss of signal (say the same type of broad band noise that Kiwi
is subjecting the XPS system to), will behave differently if it loses the link forsay 2 seconds.
Do they go scanning after the same amount of time? Do they scan faster?

As for the "It works for me so you're full of it" argument. I agree it's annoying, because
the first half of the statement doesn't actually have anything to do with the second.
The problem is, often people just infer the second part, when people say the first.
They didn't say "you're full of it". They just said "I've had no problems" which is adding
to the general sampling.
I've been on both sides of it. I have hammered XPS from the beginning over a lot of
things that other people originally considered unimportant because they'd
say "it works fine for me". Some of those things have come back to bite them.
I've caused it to fail in new and interesting ways on the bench, and been attacked as an
XPS hater. On the other hand, understanding its limitations (doesn't work in my carbon
planes for instance, more sensitive to low voltage than most other 2.4Ghz Rxs)
I've put it in a couple foamie sailplane with a nice big 6V pack, and now have probably
150 hours on it, without any problems at all. I've flown it 150+ mph while dynamic soaring.
I've flown it out to over 3000 feet near neighborhoods full of various 2.4Ghz noise, without issue.
I've never seen it lock me out for more than half a second and
that was only when I was pointing my Tx antenna straight at the plane at full range.
I've used the two way link as a lost model locator. If it weren't for that last incidental feature,
I'd probably have switched to FASST a long time ago. In fact, someone's giving me a Airtronics
RD8000 FHSS system for evaluation, so who knows. Maybe that's where I'll end up.

And of course this works both ways. When I say "I witnessed Spektrum do something
very bad, and then we reproduced the symptoms several times while ground testing",
what do I get back? "Well it works flawlessly for me, so you must be full of it."
I understand both viewpoints.

I'm neither a XPS troll or a fanboy.
My experiences with it, does not discount those of others, but I've done a lot of work
to understand fully its strengths and weaknesses, instead of just writing off the technology
wholesale because it doesn't do some thing the manufacturer claimed.
Don't ever take my technical explanations of the technology as defense of JD or his marketing
claims. The irony is that JD has done an incredibly poor job of explaining the
true strengths of the XBeePro based modules, and continues to muddy the waters
with ridiculous claims. That's why I'd like to see a real test of how the various systems
actually "function" through noise, rather than just the "stick it to JD and his BS claims" test
repeated over and over. In other words, pretend that JD had made no claims
about the system at all, and it was our job to figure out how it stacked up against
the others when confronted with real noise.

ian

[BZFrank]

Hi,

	Quote: Originally Posted by Daemon
	Because it can and does retransmit lost packets, a single antenna has 3 or 4 opportunities to hear the same packet between PPM frames...XPS's single Rx antenna may fail to hear the signal when it's at the same location as the first Spektrum antenna, but after its moved 10cm it hears the retransmitted packet at the second location. ian

But this form of 'temporal diversion' applies to *any* 2.4 Ghz system since all are sending their frames continously. The only thing XPS makes different is to resend immediately within 1 ms up to 3 times if a frame is not acknowledged by the RX. All other systems (re)send every 8 - 10 ms. BTW The '3 times resend' of XPS is a feature of the stock XBee firmware, it is not special to XPS or linked to the PPM frametime.

For the time it takes XPS to scan and select a free channel - a full energy scan of the band for all channels of an XBee Pro takes 375ms, this scan gives a metric about the momentary saturation of the Zigbee channels. Trouble is that RX and TX are in quite different environments - the one near the ground and other high above and away. So it is very likely that the energy scans of both TX and RX differs and if used to select a free channel would not yield the same result. Also during scan time the XBee modul cannot send or receive data, it just sits there and listens. This is the reason why the TX and RX cannot agree on some pre-arranged alternate channel before - they simply have no time to scan as doing so would lead to a significant number of missed frames and therefore lag.

Looking into the time it takes to negotiate a new channel: To switch between channels (without scanning if the channel is free) takes 15 ms for XBees. Then some dwell time is needed to listen in on the channel if data is received - say 25ms max. Makes for 40 ms per channel or about half a second (480 ms) to scan in on all 12 channels. Now take into account that such a scan may not work initially since the TX may have selected a channel that looks free on the ground but is saturated in the air or temporarily blocked by shadowing or multipath interference. So several scans may be needed for the RX to find a working channel.

Frank

[KrisW]

	Quote: Originally Posted by Daemon
	You seem to be under some misconceptions about what technologies XPS uses and how they work, as well as what Spektrum does for that matter. Some of them fairly common, some of them you really should know better. Hopefully I can clear them up. SNIP But like you, I think this is the one case where it'd sure be nice if it did hop. Although I don't want it to take 5-15 seconds either. A normal cold boot of XPS (initial scan and link, usually only takes about 3 seconds though), so it should never take longer than that. It's only got 12 channels to scan. ian

ALL RIGHTY. . . I think you just took my own record for "longest single post on an RC forum" Great job.

You just refuted every "preconceived notion" that is out there, about Spektrum. Thanks. . it was hard to get so many of them into one post.

Now a couple of legitimate hits on your little "experiment" with the 6100 unit.

As someone else already noted, the 6100 is a "Park Flyer" setup, and is not meant for longer ranges or higher interference. I have tried the "Block the signal with your body" move on a couple of the DX-6 setups flying from my home field including my own, and have watched foamies fly away until they are a dot, and barely seeable, but still function perfectly with total control. We are talking at least 1000 feet here. So, that comes down to individual setups, and the functionality of the receiver in question. Electronics being what it is, the setup in the plane in question migh thave had some problems which caused the lack of range, though with the 6100 series receiver any attempt at longer range flying was probably a bad idea to start with. In no way does it reflect the capabilities of the 7000 and 9000 series pieces. One system that fails consistently, means one system that has a problem, and should not be considered normal for every system out there.

Second point, for real this time. . Carbon fiber is one reason I am going to hold on very tightly to my 72mhz equipment. With the low power output of the 2.4g systems, coupled with longer ranges than normal and very small receiver antennae, it's a given that an airframe with large amounts of RA materials like Carbon Fiber would be a nightmare for a 2.4g user. Even the guys using 72 mhz have difficult with it, and it almost always requires external antennae. So, no flyer, using ANY 2.4g equipment, unless they really pump up the power and run some very different antenna pieces, is going to have a good time with a CF latticework or solid CF skinned aircraft. It's LOGICAL that this would occur, no matter what frequency band you are transmitting on. So, repeating the information aobut 2.4g having problems with CF is just reinforcing the obvious for every radio system out there.

I still have not seen an iota of information pointing to any advantage or superiority for the XPS equipment over Speltrum. That, in and of itself, relegates XPS to 2nd tier status, especially with all the very open testing where XPS will not frequency hop at all. In fact I see the exact opposite, even in showing a potential problem with the Spektrum equipment that is only logical if one thinks about it. EVERY system can be jammed or interfered with. But XPS cannot be proven to frequency hop consistently, and it's use of a single channel, and having a default preference for the same channel over and over again, makes it even harder to accept it as a viable alternative in an RF unfriendly environment.

One last point . .your "preconceived notion" concerning the moving of an aircraft exactly 10cm so that the receivers catch a reflected or mirrored signal is pretty bogus. C'mon. . eXACTLY the amount needed to cause a problem? Who are you kidding here. Theoretically it may actually be possible. In real life the aircraft would have to be moving at an astronomical speed in order to get a pulse train of information confused between the receivers. Reflections would have severely attenuated signals (by a factor of 5-10x usually), and harmonics would be ignored. I'm pretty sure this "theoretical" shortcoming is well addressed with the firmware and software that Spektrum uses, and I pretty much agree with their position on their systems ability to negate the affects of these problems and multipath receivers.

With Spektrum you get. . a larger choice in frequencies .. . 2 frequencies of use at the same time and (usually) are spaced well apart in different areas of the 2.4g band. . . multiple receivers and antennae to help assure multi-path reception. With XPS you get. . one channel at a time. . 12-16 channels, a pack of BS from the manufacturer, a single path antennae that cannot possibly work the way the manufacturer claims, and a history of planes falling out of the sky. with FASST you get true frequency agility, but there are issues with that which I am uncomfortable with (Latency. . possibility of getting lost if your radio loses link in a high noise environment), and the GUID confusion episode is probably not an isolated incident.

Suffice it to say, that any of the 2.4g systems can have a problem, for whatever reasons. . BUT. . . I know which one I will NOT be using. . . .

[ricoalonso]

Edit: Sorry, I got lost after reading those series of loooonnng posts...after my morning coffee then I realize I went off topic, so I deleted

But, just the same, much thanks to Kiwi for all your time. Pls post the next thread for FASST or SPEKTRUM tests. Enough with XPS already as I think everyone has given it more than the attention it deserves.

Rico.

[Kiwi]

Ian, Frank,

Guys I really do appreciate you coming in here and helping explain what I am unable to or dont fully understand yet. I am more than willing to share data, equipment or what ever if you are willing to make this a team effort. If you guys can do some things I cant then I have no trouble getting the Fedex man to move a parcel one way or the other.



I will be taking delivery of a new Spektrum radio tonight so that pretty much completes my collection although I do not have an idea on Airtronics yet. There's still one more coming that the birds are chirping about that might just blow the socks off everything to date but its a while away and still in the lab. Seems some people do a lot of bench testing before they launch a product as opposed to those who use the wait and see method.

Yes every 2.4 Ghz RC system can be shot down. Not a doubt in my mind about that but then again you can shoot down 72 Mhz, 50 Mhz, 36 Mhz a whole lot easier by just turning on your Tx when you dont have the pin.

I have no bone to pick with XPS other than the fact it is sold as a frequency hopping robust system that has the ability to skirt a dirty channel if it encounters one. To date no one has ever been able to simulate that happening on a bench or in the air. That bugs me as I know a lot of guys who installed XPS on perfectly setup very expensive models and they lost them. Every one of those guys purchased XPS to protect the investment from potential interference and shootdowns.

All I want to do is prove that the products that have been sold to date are actually what they are advertised to be.

The FASST, ASSAN, SPEKTRUM testing is about to begin. I have no preconconcieved ideas on what I will find. Its just fun to find out what makes them all tick.

[Kitman]

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.

Aristo1963, I can assure you as Moderators for Flying Giants, he has not deleted any posts here, we have that control! By be on other sites, but here we are straight up!

Kitman

[Pale Rider]

	Quote: Originally Posted by Daemon
	"To appease the masses", he might say. I'm not a cheerleader for JD.

Dont get me wrong--Im not saying you are a cheerleader at all...Just seems strange that he is using that line for this as well as for the development of remote rxs too. I think its just a way to get around improving his system without admitting there was ever anything wrong to begin with.