[XJet]

Several independent tests (by different parties) has proven that the XPS system does *not* reliably frequency hop (in fact no frequency hopping has ever been recorded by independent testers).

Even XPS themselves have admitted that when confronted with a sudden rise in the noise level (or a strong interfering signal) XPS will not hop frequencies -- meaning loss of control and lockout.

This issue was raised initially on RCG and once the evidence began flowing, the posts were deleted by JD.

To put this in perspective however, it doesn't mean that XPS isn't a practical 2.4GHz solution -- it simply means that it *is* more vulnerable to some forms of interference than either Spektrum or Futaba.

Futaba, thanks to its constant frequency-hopping remains virtually unaffected by any strong signal on any of its 250 or so operating channels.

Spektrum uses two channels from a selection of 80 so a strong signal on either one of those signals will not cause loss of control because the other frequency will continue to deliver data.

XPS however, starts off on the back foot because it only has 12 frequencies available to it (versus 255 on Futaba and 80 on Spektrum) and absolutely no way of coping with a sudden sustained interference source.

From a practical perspective, this means that if you fly from a remote field with little or no other 2.4GHz activity around then XPS is no better or worse than any of the others.

However, if you fly in an environment where the noise profile of the 2.4GHz band is both cluttered and highly variable then the XPS system becomes significantly more susceptible to interference than its peers.

The reality is that something as simple as one of those 1W 2.4GHz video transmitters up to a mile or so away could knock your plane out of the sky by suddenly dumping on the frequency XPS has chosen to use. Spektrum wouold fall back to its second channel, Futaba would simply hop past the noise -- XPS coudl well have nowhere to go and fall into failsafe.

This revelation could explain the few instances where XPS-equipped models have flown perfectly well for hundreds of flights and then (seemingly inexplicably) locked out and crashed. It also explains why some folks have no problems until they opt to fly from a different location.

It may also explain why some folks (such as a handful in France) lost several models to XPS while Futaba and Spektrum systems operating at the same time were unaffected.

So, if XPS is working well for you -- that's great, long may it do so.

However, be aware that you *are* more vulnerable to the sudden appearance of strong noise or interfering signals.

JD initially admitted that this was a problem and that XPS was working on a fix -- then seemed to have a change of heart and deleted many posts in the thread where the evidence was presented.

He then began trying to discredit those who did the tests and presented the evidence (if you can't argue the message, shoot the messenger).