I think this might be a better way of expressing it?

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Note added at 3 heures (2016-10-13 20:55:02 GMT)
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portée de 700 m [2300 ft] en mode sans fil

for anyone who might not have understood my intention

Personally, for the FR version, I'd be inclined to leave out the feet altogether, as not adding any additional meaning to a FR reader.

I'm assuming, of course, that what they are saying is that our device has a greater range than most others on the market in this field.

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Note added at 20 heures (2016-10-14 13:55:56 GMT)
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I take Robin's point about adding 'mode', lest it should lead to an implication that any other mode was also possible.
However, I do favour the inclusion of the term 'sans-fil', but can't help feeling that using it on its own (as Asker originally proposed) doesn't really work in FR in quite the same way as it does in EN.

Maybe one could add some other word like 'communication sans fil'?

BTW, I don't believe this is 'official' Wifi — that range sounds too great for it to be Wi-Fi, at least according to the normal standards.


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Note added at 20 heures (2016-10-14 13:56:34 GMT)
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If not, then simply fall back on 'portée de 700 m [2300 ft] en sans fil'?