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Quote: Originally Posted by Daemon |
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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 |
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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.