Independent tests prove lack of frequency hopping with XPS

[JEFFRO503]

	Quote: Originally Posted by Mike Busutil
	Sure thing Jeffro! Just for you

Mike have you ran both those 3w's? That 275cc has got to be a friggin' brute! still in awe by .......awesome man , awesome!!!

[Mike Busutil]

	Quote: Originally Posted by JEFFRO503
	Mike have you ran both those 3w's? That 275cc has got to be a friggin' brute! still in awe by .......awesome man , awesome!!!

I have only ran the 275.......the 212 is for another project, a 50% Christain Eagle.

[BaldEagel]

Are you two guys trying to hijack this thread? you are way off topic, please take it somewhere else.

Mike

[JEFFRO503]

sorry man......i was just impressed by Mike's 50% edge and i got side tracked.....who wouldn't?

carry on.......

[Kiwi]

-Well still going strong as ever here I see.

I'm going to fork out some change and buy an XPS module and Rx and do the tests all over again but using some of the parameters you guys are asking for. That is set the transmitter some 50 ft from the Rx and place the noise source in the middle so it is far enough away so as not to swamp the front end. However I make it very clear that I did not swamp the front end last time because if I had it would have never gone into fail safe (as it did) and it would never have continued functioning once the signal passed the selected XPS frequency.

But this time I hope to have some more systems to test. I have placed an order for the new Frequency Hopping system kit from China that appears to be very similar to FUTABA in many ways, plus I have placed a forward order for a new system from Germany.

The new Chinese system is full FSS and reported to have an 800 meter operating range on the ground. I would expect that to triple in the air at the very least but lets wait and see.

That will give me five different manufacturers products to compare against each other. This time an Apples vs Apples test.

With some luck the military friends I have think they can help me with the signal generation and test equipment I need to make this a bit more scientific but thats not a 100% fact yet and depends on the mood of the General on the day.

I am going to repeat myself here for the tenth time however and that is I am not on a witch hunt, I do want to find what system is the most robust for MY OWN PERSONAL INTERESTS and I would like to share these with others who are likewise interested.

It is not a competition to see who is the worst, but I do want to see who is the best. An old mate of mine always said that being second means your the first of the last.

Am I biased about this?

No I dont think so, I use Spektrum, ASSAN, FASST today and still have my 72Mhz stuff loyally providing me with a robust service.

Do they other have faults or weaknesses.

YES!!!! every one of them has some kind of weakness or lack of perfection to put it nicely.

FASST has a heat issue, FASST had a GUID issue, FASST has zero data retention, logging or monitoring system.
XPS has its fair share least of which is a reliable frequency agility.
ASSAN has some issues with servo jittering and initially a lack of a GUID.
SPEKTRUM had a hard run for a start and countless issues.

The thing is most of the manufacturers are actively working on fixes while some have taken the ostrich approach.


And so it goes on. They all can be better and often at little cost or effort to the manufacturer. Some of them just lack the will to get better, they are in a comfort zone and the only way you move them from that is by consumer demand. This thread is avery small wedge into that comfort zone and hopefully it will move some of the players we discuss to improve.

How many people here would like to see a data logger for the FASST system so you can see lost packets, lockouts, fail-safe, signal strength just as an example.

What do you see as lacking with any of the products available today?? What do you see needs to be done better.

If XPS is copping the brunt of the confrontation its is only because people see an issue with it. Real or unreal, warranted or unwarranted it does not matter. If a weakness is perceived then people will persistently attack that weakness. Its human nature.

I will keep you posted on how I go once I get my next lot of product but in the time being lets keep this thread as least personal as possible and keep trying to build a better mouse trap. As I said above if we rattle the bushes the manufacturer will often listen, that way consumer demand gets the better mouse trap we are all looking for.

[dirtybird]

	Quote: Originally Posted by JEFFRO503
	hhmmm??.....I don't think XJET is showing an ego with this. I believe he's just stating the facts. He has every right to toot his own horn ( him and Kiwi both) for all the work and results they have came up with. Still after ( what 117 pages ??...i forgot to look ) JD has had a very , very long time to either fix his problematic gear , or at least show us 'some" kind of proof that it hops they way he says it does. But still........nothing. Honestly.....i really think it would be cool if JD came clean. And was just up front and honest about it and said " Hey......i've got new things in the works , sorry my older system didn't hop" XJET and Kiwi both seem very keen on how these systems work , it would be REALLY COOL if they we're helping Jim make his product better and safer for everyone. Also.....i would just stick with Futaba or JR/Spektrum just because of all this nonsense. To much bad press from waaaayyy to many users. I think they out weigh the good by a long shot. I'm not willing to take a chance on that.

After many years as an aerospace test engineer, I learned one thing especially. You must be very careful in the determination of your results.
It take a big ego to say you know more than the designer of the equipment you are testing. The designer has spent many hours making the item ready for release. He will know more about his design than anyone else.
The most important parameter of a receiver is its sensitivity. I don't see any of those testers testing that. If a receiver is 3db or more better in sensitivity all else is secondary.
I don't see xjet offering his "expertise" to Futaba or Spectrum. Why? BECAUSE HE CAN'T GET A RISE OUT OF THEM.

[Woketman]

	Quote: Originally Posted by dirtybird
	After many years as an aerospace test engineer, I learned one thing especially. You must be very careful in the determination of your results. It take a big ego to say you know more than the designer of the equipment you are testing. The designer has spent many hours making the item ready for release. He will know more about his design than anyone else. The most important parameter of a receiver is its sensitivity. I don't see any of those testers testing that. If a receiver is 3db or more better in sensitivity all else is secondary. I don't see xjet offering his "expertise" to Futaba or Spectrum. Why? BECAUSE HE CAN'T GET A RISE OUT OF THEM.

After 27 years or so of space vehicle design and analysis, there are many things I've learned: one of which is that I DEFINITELY believe Xjet over JD. JD is a known bul_s_itter and has not a pico-liter of credibility remaining!!! He has lied to all of us on multiple occasions. Anyone who still beieves a word that JD says is a fool, plain & simple.

[acrorc]

	Quote: Originally Posted by dirtybird
	The most important parameter of a receiver is its sensitivity. I don't see any of those testers testing that. If a receiver is 3db or more better in sensitivity all else is secondary.

I disagree strongly with that statement. IMHO the receiver needs to be only sensitive enought to provide a useable range. I would rather have a less sensitive receiver and stronger transmitter in our application. The ability to reject interfering signals and to continue to provide a reliable control link while interference is present is way more important.
BTW Futaba proved this several years ago with a very sensitive receiver that had some problems.Their recommendation was to shorten the antenna on the receiver to reduce sensitivity.

The best setup might be a "diode detector" and a 5 watt transmitter but today our RC sytems are based on commerically available parts and I might add on the FCC rules for the frequencies we use.

John W.

[dirtybird]

deleted

[dirtybird]

	Quote: Originally Posted by acrorc
	I disagree strongly with that statement. IMHO the receiver needs to be only sensitive enought to provide a useable range. I would rather have a less sensitive receiver and stronger transmitter in our application. The ability to reject interfering signals and to continue to provide a reliable control link while interference is present is way more important. BTW Futaba proved this several years ago with a very sensitive receiver that had some problems.Their recommendation was to shorten the antenna on the receiver to reduce sensitivity. The best setup might be a "diode detector" and a 5 watt transmitter but today our RC sytems are based on commerically available parts and I might add on the FCC rules for the frequencies we use. John W.

Well you and I disagree.
With a more sensitive receiver you can reduce the sensitivity with the automatic gain control(AGC). This reduces its bandwidth and makes it less sensitive to noise and interference.
Futaba's problem was the AGC did not work properly.
With a diode detector you would be wide open to any interference. Futaba tried this in the begining with poor results. World Engines also had a receiver based on this principle. They had to withdraw it and send out replacements.

[Chris F]

	Quote: Originally Posted by dirtybird
	I was hired last fall to do Safety of Flight Tests on the flight computer for the 787 for which I was paid $15,000/mo. I don't think they would have done that if they considered me to be a fool.

I know others have also stated their credentials to gain credibility, but please let's not start on how much you get paid, it makes you look like something I hope you are not. Convince us with your knowledge instead.

[Woketman]

	Quote: Originally Posted by dirtybird
	If you are what you say you are you must have access to some decent test equipment. You are young enough to still be active in the industry. Why don't you get together the proper test equipment and do some accurate tests. Start with receiver sensitivity and test the other systems as well. I have met JD and talked to him and watched his demo's. I believe what he has said to me. I was hired last fall to do Safety of Flight Tests on the flight computer for the 787 for which I was paid $15,000/mo. I don't think they would have done that if they considered me to be a fool.

That is nice and condescending: the "if you are what you say you are" part. And I am exactly what I say that I am. But I am not a volt-head. I am a structural engineer/stress analyst. I have no access to electrical stuff.

What the heck do any of us care about you working on some Boeing stuff for?

You say "I have met JD and talked to him and watched his demo's. I believe what he has said to me."

Well, as I said previously "JD is a known bul_s_itter and has not a pico-liter of credibility remaining!!! He has lied to all of us on multiple occasions. Anyone who still beieves a word that JD says is a fool, plain & simple."

'Nuff said!