Independent tests prove lack of frequency hopping with XPS

[wrightme]

	Quote: Originally Posted by BaldEagel
	Late in the day was alluding too the fact that you joined FG in Jan 2008, late in the day for this disscusion. Mike

Then that statement is even more questionable.

Reality:

This thread started on 21DEC2007.

I joined FG on 04JAN2008.

I posted in this thread on 06JAN2008, page 18.

This thread is now into it's fourth month, and 75th page.

"Late in the game?" Maybe....maybe not......

Did you look through the posts prior to YOUR first post in this thread? The one from MARCH 8th?

[Chris F]

I posted a question in the XPS Forum at RCG (Questions for Jim Thread), which was deleted today. I simply asked when he was going to show us the video he promised of XPS hopping. He deleted it and posted this, "This is a forum that we pay for and we will delete any content that we feel is inappropriate".

Well I'll take it that Jim has no intention of fulfilling his promise of providing proof that his XPS system hops, and that asking him to fulfill his promise is "inappropriate".

I was interested but now I just couldn't buy anything from this guy, even if it was "as advertised".

Here is a link to RCG where JD explains where he is up to with the telemetry for anyone interested.
http://www.rcgroups.com/forums/showp...19&postcount=4

[4*60]

...

[KrisW]

	Quote: Originally Posted by zoomer260
	Guess you poor souls would have to have missed all the rc fun when it was AM huh ? And When PPM was the next thing you would have all jumped up and down about how great IT was ! Untill the next greatest thing comes along. I personally would order a 9303 2.4 system yesterday if I could afford it, I'm looking at the Spektrum 7 because I can't right now. The only plane I ever lost due to radio link problems was with PCM lockout. Discounting the idiot that told me his PPM radio was off and I could have the pin when it wasn't. But I wouldn't "hide under a shelter" because some "old school" equiptment was being used. All our planes are "potentially" unguided missiles regardless the radio system used.

When I started into RC back in 1975, I had a choice. . AM or FM. . I chose FM because all the AM guys were having SOO many problems due to the CB radio craze going on back then. FM was up on the 72mhz band, AM was stuck on 27mhz with all the truckers. When I got bqack into the hobby 11 years ago, I immediately went with PCM due to it's many advantages over PPM.

I find your attitude extremely ignorant when it comes to the safety of those around you, and trying to give me a hard time for being prudent is really wayyyyy off base.

We stand under shelters because there is a very real danger, but the fool flying the plane, like you, thinks the danger is acceptable. It's not acceptable, in any way. Control loss at any time should be immediately rectified. When it's not, the PERSON has a major problem. Which is why XPS users worry me.

I've seen too many instances of people with half-witted attitudes toward radio safety FINALLY cause a big enough problem that everyone stepped in and shut them down until they fixed their planes. It should not take that. At the first hint of a problem the plane should be on the ground or examined very carefully until the problem is determined and then the situation resolved. 2 years ago, at JN, I collared Kiwi and another guy for almost an hour while I sorted a weak receiver on my MX-2. At the FIRST hint of a control issue I had the plane on the ground, and then through careful examination and testing we determined which receiver was actually weak, and I immediately fixed the problem.

Some people don't take it seriously enough. PPM users get a lot more "glitches" than PCM, which is why I only fly PCM systems on anything larger than a foamy.

I'm not missing a damned thing by making sure the guys using PPM don't injure or kill me. You may laugh at that, but it takes one mistake to make it happen.

Feel lucky, punk??

[BaldEagel]

	Quote: Originally Posted by 4*60
	Don't know how XPS can be compared to PPM. No one can shoot me down like they tried on 72Mhz or just cause scary uncontollability, just by turning on or not turning off. Failsafe is user defined,with XPS and part of the package which puts in into the PCM area. A whole bunch of XPS, Spektrum, FAAST, modellers can fly at once and all enjoy, without pins. Seems like there are some positives.

So what we have here is a system that is only as good as PPM, with in flight lock out instead of a glitch that we can fly through, if you are prepared to fly XPS/Graupner with this in mind, then fine, but please don't fly near me or any of my relatives, or friends, or any humans, and I also like cats and all other mamals. LOL

I take it then, that you refuse to be near anyone who uses PPM as well? That must
really limit your time at the field.

ian

Luckly most of our club members are thinking people and don't use PPM on this interfearance prone site.

Mike

[BaldEagel]

	Quote: Originally Posted by KrisW
	Too bad, when XPS glitches, you can't regain control. . . . . But, the glaring part of BaldEagel's post is. . why is XPS having problems when 72mhz PCM is not?? I thought 2.4 was supposed to be better, have a stronger link, use GUID and all sorts of neat things to lock onto signals, and be our Saviour. . . Now. . THAT is scary. . . . .

Kris

Two points, when XPS glitches you loose control for a second or two and then control comes back, it goes into lock out, ie it stays at last command if the interfearance is not prolonged at that point it I presume goes into fail safe, I only used the system once in the air when it went into lock out four times, it did not go into fail safe, and I am not going to give it the opertunaty to in one of my planes.

As you say the glaring point is that this system is having problems on 2.4Ghz where 35Mhz PCM does not (UK)

Mike

[Flyfast1]

	Quote: Originally Posted by Chris F
	Here is a link to RCG where JD explains where he is up to with the telemetry for anyone interested. http://www.rcgroups.com/forums/showp...19&postcount=4

Chris,

Thanks for the link to the upcoming telemetry station that XPS will be offering. I look forward to being able to review real time flight data, such as engine temp, engine rpm, battery voltage, etc.

I have been flying XPS for about 10 months in everything from small glow planes to 1/4 scale warbirds with large gas engines and the system has worked flawlessly. I have not had any issues with blind spots behind even 100cc size engines on my planes. I did have one setup in a 1/4 scale ME109G where my range test failed at a particular location with respect to the plane. This problem occurred because when standing at one particular spot relative to the plane, the receiver was directly behind a large aluminum air tank for my retracts. Moving the receiver to a different location away from the air tank completely solved the problem.

A couple of points about XPS that I don't see discussed much:

1. XPS does select a clean channel on startup. With my 72Mhz systems, I had no way of knowing whether there was interference on my channel and even if I did know, had no way to change channels. In many situations with 72MHz systems, there was known interference on my exact channel in the form of other flyers on my frequency. The only way to address this conflict was with a transmitter impound. Not a huge problem at my field, but I was always concerned about it at large fly in events.

2. XPS does bind the transmitter to the receiver, so even if there are other flyers on the same frequency, we should be able to fly together without any issues. I think this is a huge improvement over 72Mhz where anyone with a transmitter on my frequency could control my plane. This issue is completely addressed by the XPS system (and other 2.4GHz systems as well).

3. XPS does retransmit data if an ACK is not received by the transmitter. My understanding is that this can happen several times, if necessary, before the next frame. With a 72MHz system, if the data does not get through uncorrupted, then you have to wait for the next frame. May not be a huge issue because a lost frame every now and then may not be noticeable, but should result in fewer lost frames. My understanding is that XPS will be doubling the frame rate with the next firmware update.

I am not trying to compare 2.4GHz systems here or say that one is better than the other. But I do think that the XPS 2.4GHz solution is much better for me and safer than my 72MHz systems. I have a fair amount invested in XPS and am completely happy with it, but perhaps one day I will also buy another 2.4 GHz solution.

-Ed B.

[Pale Rider]

Ok question for the experts---Is there a greater degree of latency between the module-based FAAST system versus the DSM2 that Spektrum uses ? If so, is it even noticeable.

[sweetpea]

	Quote: Originally Posted by Chris F
	I posted a question in the XPS Forum at RCG (Questions for Jim Thread), which was deleted today. I simply asked when he was going to show us the video he promised of XPS hopping. He deleted it and posted this, "This is a forum that we pay for and we will delete any content that we feel is inappropriate". Well I'll take it that Jim has no intention of fulfilling his promise of providing proof that his XPS system hops, and that asking him to fulfill his promise is "inappropriate". I was interested but now I just couldn't buy anything from this guy, even if it was "as advertised". Here is a link to RCG where JD explains where he is up to with the telemetry for anyone interested. http://www.rcgroups.com/forums/showp...19&postcount=4

That was actually a reasonable post. Time will tell if it all holds true.

[jonkoppisch]

I guess there will be a surge on guys buying laptops...

[XJet]

I find it interesting that JD claims:

	Quote:
	We plan to go to a 100Hz (10ms) frame rate with direct data (no PPM conversion), making us the fastest radio system in existance

This is piffle! What "direct data" stream is he going to access?

Since the kind of transmitters into which XPS currently fits only spit out one frame of data every 20mS, all he's doing is sending the same data twice -- why?

And since modern servos (some heli-specific hi-framerate servos excepted) are only able to accept data at 20mS intervals, half of that data will have to be thrown away anyway.

Why does JD feel he has to "one-up" the competition by doing this kind of thing -- promising benefits that don't exist.

Ah, but he says that:

	Quote:
	All of this is in preparation for the new transmitters being produced

Which transmitters is he talking about? XPS transmitters?

Or is someone else planning to build a 100Hz transmitter? If so, why would they make it form/electrically compatible with existing FM modules that are only able to provide enough bandwidth to support a 50Hz frame-rate?

Maybe he knows something I don't (it's quite possible) but if not, I wish JD would simply sell on reality rather than constantly having to tout the system as being something it's not.

[jonkoppisch]

	Quote: Originally Posted by XJet
	...I wish JD would simply sell on reality rather than constantly having to tout the system as being something it's not.

But that wouldn't be jd then... That would be..... spektrum or futaba or jr or....

Was all the info released today about the telemetry etc? You know... April 1st???

I hear they're gearing up for Toledo with some new advertising.... & a whole new set of beta testers..

[XJet]

	Quote: Originally Posted by jonkoppisch
	Was all the info released today about the telemetry etc? You know... April 1st???

It's already April 2 here :-)

[jonkoppisch]

Then the jokes only on us?

[zoomer260]

	Quote: Originally Posted by KrisW
	When I started into RC back in 1975, I had a choice. . AM or FM. . I chose FM because all the AM guys were having SOO many problems due to the CB radio craze going on back then. FM was up on the 72mhz band, AM was stuck on 27mhz with all the truckers. When I got bqack into the hobby 11 years ago, I immediately went with PCM due to it's many advantages over PPM. I find your attitude extremely ignorant when it comes to the safety of those around you, and trying to give me a hard time for being prudent is really wayyyyy off base. We stand under shelters because there is a very real danger, but the fool flying the plane, like you, thinks the danger is acceptable. It's not acceptable, in any way. Control loss at any time should be immediately rectified. When it's not, the PERSON has a major problem. Which is why XPS users worry me. I've seen too many instances of people with half-witted attitudes toward radio safety FINALLY cause a big enough problem that everyone stepped in and shut them down until they fixed their planes. It should not take that. At the first hint of a problem the plane should be on the ground or examined very carefully until the problem is determined and then the situation resolved. 2 years ago, at JN, I collared Kiwi and another guy for almost an hour while I sorted a weak receiver on my MX-2. At the FIRST hint of a control issue I had the plane on the ground, and then through careful examination and testing we determined which receiver was actually weak, and I immediately fixed the problem. Some people don't take it seriously enough. PPM users get a lot more "glitches" than PCM, which is why I only fly PCM systems on anything larger than a foamy. I'm not missing a damned thing by making sure the guys using PPM don't injure or kill me. You may laugh at that, but it takes one mistake to make it happen. Feel lucky, punk??

Now, now Kris ol' buddy, no need to get nasty. What I said was completely true and you confirmed it by saying you jumped on the FM PPM bandwagon because it was the "next greatest thing".

All I said that had anything to do with what YOU said was the "potentially unguided missile" part. Which if you can't get it through your head that ALL our planes are potentially unguided missiles you completely missed my point.

One thing that has bothered me about people on this site is the "safety" factor. Most (as do you) think that a large airplane turning a BIG prop really slow (6000RPM) is somehow 10 fold more dangerouse than a small plane turning a small razor blade APC 14000 rpm. IT AIN'T. That 14000 will cut you completely to pieces in an instant. On a .40 size plane.

I hear about duel recievers, duel Rx batts, power expanders all these great things (that work) In the name of safety because it is on a BIG plane. Bullcrap. It is the investment that is being protected.

I have only seen one pilot intentionally plant his crippled plane in the name of safety. And it was a Jet pilot at a Superman Rally. I was so proud of that guy. Everyone else tries their best to get the crippled "investment" back to the strip. Probably including ME.

I planted a .40 size quickie plane once on purpose and I still am proud I did it. Might could have saved it, I decide it wasn't woth the risk to others. If I had been alone at the field no doubt I would have tried.

So please, no more BS about safety and the size of the plane concerning equiptment. They all deserve the best you can afford.

That said, doesn't mean if you can't have all the latest and greatest you should be grounded.

And Kris, sorry to vent and it doesn't all concern you. Just that I don't understand how a .40 size plane turning 14000 rpm going 150 MPH can be in any less need of all the redundency and "safety factor".

And I have survived several "potentially fatal" injuries so yeah, I feel very lucky.