Independent tests prove lack of frequency hopping with XPS

[Pale Rider]

Great info Kiwi!! Looking forward to reading more..

Here is a question--does Spektrum toggle back and forth between the 2 channels it picks when it first links up ? Meaning during a flight if the first channel is swamped and it goes to the second channel, does it stay locked onto it (2nd channel) for the duration of the flight ?

[jonkoppisch]

Someone else may have made the xps system hop although it's under strange circumstances...

	Quote: Originally Posted by Eddie-extra
	Hi, Ok I'll try to repeat todays results.... Tested equipment in garage prior to taking it down the field, had a friend over with his Futaba system so thourght we would try and see if there was any issues with cross talk interferance or the like, I had my XPS system powered up and working on my plane without the TX aerial connected, the usb Analyzer on my computer was monitoring the 2.4 bandwidth showing my TX on channel 10 and a few other much smaller signals probably the local computer networks etc. My friend then powered up his Futaba TX to see if would 'interfeer' in any way there was no noticable problems with the XPS system apart from a slight increase in servo buzz he then touched the XPS receiver with his Futaba aerial (extreme i know) whilst the xps Tx aerial was still not connected again no perceivable problems with the xps system. During this time the readout on the USB analyzer showed all the channels were now varying/ peaking with signal which wasnt there previously. The Futaba was then turned off and all the channels returned to no significant signals except a strong signal on chanel 20 and nothing on 10. The XPS system was still working. We then went to the field and flew.... my system had a lockout due to range problems his flew perfectly.....

http://www.rcgroups.com/forums/showt...13#post9125803

[ricoalonso]

Kiwi,
Since someone from RCG was able to make XPS hop by using the FASST signal as the noise source, maybe aside from your plan of subjecting the XPS to a '3D' noise that you can also consider subjecting XPS to a repeatitive (off-and-on) low-level noise.

Since FASST is actually hopping all around the entire band, it will mean that it hit the frequency which XPS is currently using so many times in a given time period. So, maybe (just maybe) if XPS is hit by a 'repeatitive' short-burst, low-energy noise then eventually the hopping is triggered.

Of course, IMO, this doesn't make sense in real application.

Just a thought..
^R^.

Edit:
I just thought of this while posting in another forum... I think I remember XPS saying that the 'counter' is reset when there is a sudden rise of noise.

Now, that makes me wonder about this counter... is it a 'counter' of occurence? If so, maybe it's keeping count of the short-burst noise and a threshhold is set. Maybe once the count of occurences hit the threshhold then the hopping is triggered?
++++

[sweetpea]

	Quote: Originally Posted by JEFFRO503
	Sweatpea..what b do you mean they are the same? All older radios for ground control we're 27.something before the big switch to 75mhz. My M8 ( which is one of the top of the line radio's for surface) is 75mhz . Are you saying that 27mhz and 75 mhz is the same? i don't get it.

Nope......what I'm saying is Ch 4 is 27mhz. It doesn't matter if you are AM or FM. My M8 (I've got one also) is 27mhz FM. I have channels 1-6 in the case. 27mhz only uses Ch 1-6. Anything higher is 75mhz. (on ground freqs)


Here is a good link that will show you all the available freqs and the number that is associated with them.

http://rcsource.hobbypeople.net/faqs/freqlist.htm

[JEFFRO503]

	Quote: Originally Posted by sweetpea
	Nope......what I'm saying is Ch 4 is 27mhz. It doesn't matter if you are AM or FM. My M8 (I've got one also) is 27mhz FM. I have channels 1-6 in the case. 27mhz only uses Ch 1-6. Anything higher is 75mhz. (on ground freqs) Here is a good link that will show you all the available freqs and the number that is associated with them. http://rcsource.hobbypeople.net/faqs/freqlist.htm

AAHHH!!.....i get it! After running the 1/8 scale buggies and truggies for about 4 years , i didn't know this. thanks for the info man.

[sweetpea]

No prob.

Back to the Hopping of XPS......

This most recent test was a little vague on details but here is the skinny.

A guy turned on XPS...noted it was on Ch 10. Then he turned on a FASST system. He noticed RF on all the available freqs (though it was very low in power). Assumed it was FASST hopping around. He then turned off FASST and noticed that XPS was now on Ch 20(or was it 30?).

This wasn't a very technical test at all and it raises more questions.

[ricoalonso]

	Quote: Originally Posted by sweetpea
	No prob. Back to the Hopping of XPS...... This most recent test was a little vague on details but here is the skinny. A guy turned on XPS...noted it was on Ch 10. Then he turned on a FASST system. He noticed RF on all the available freqs (though it was very low in power). Assumed it was FASST hopping around. He then turned off FASST and noticed that XPS was now on Ch 20(or was it 30?). This wasn't a very technical test at all and it raises more questions.

Yes, someone from RCG had tested and noticed that his XPS system hopped from Ch-10 to Ch-20 after they turned on a FASST system, using it as a noise source.

This is why in my post #579 above, I am requesting Kiwi for another test scenario. I am just thinking, that maybe XPS is using a noise occurence counter and a threshhold set for occurences to trigrer a hop.

^R^

[jonkoppisch]

It wasn't quite that simple.. See post #578, but it did seem to change channels although later he had problems with the xps

[ricoalonso]

	Quote: Originally Posted by jonkoppisch
	It wasn't quite that simple.. See post #578, but it did seem to change channels although later he had problems with the xps

Yeah, that's right. I feel sorry for the person. He said he had a poor range-test and someone else pointed out that based on the spectrum graph he posted, his Tx module seems to be transmitting at low power. For now, the cause is still unknown but the poor range test maybe some clue.

But as for the hopping, I still think that maybe by applying multiple short-bursts, low-level (just enough for XPS to notice but not enough to lockout) noise to XPS for several times within a time period may trigger the hop. I think that's why JD made mention of a 'counter' being reset if the noise has sudden rise.

^R^

[wrightme]

	Quote: Originally Posted by Kiwi
	OK I have some new software that I hope will show you how that works. It scans the X axis and Y axis and also the third access (D for me) but you techies will have a better name for it.

The answer is "Z". Check with anyone graphing in 3 dimensions, the third is Z.

[airborneSGT]

Would you guys trust the XPS in 35% and up planes? Toy planes are least of my concerns now but I do have a system close to being ready in a smaller plane.

[zoomer260]

This thread is now getting to be very interesting reading and I'm fairly certain that (by now) JD is watching. Wonder why the company doesn't defend it's product ? I've wondered this throughout this entire thread.