Are "RF" and "wireless" defined by their frequency or their media?

1/30/2010 12:00 PM EST

Generally, this is not is not a problem, since the context of the discussion and expertise of the people we are talking to eliminates, or at least minimizes, ambiguity and misunderstanding. (I did, however, attend one conference where there was a heated argument about some aspect of "IP"–it turned out that one of the arguers meant intellectual property, while the other was referring to "Internet protocol"! And I'm sure they weren't talking about "intermodulation product.").

But what do we mean when we say RF? Do we mean radio frequency? OK, but what's a radio frequency? In the early days of radio–and I am talking Marconi-era here– radio operated down in the tens of kilohertz at its highest, which is almost DC from our present vantage point. But it was radio, in every sense of the word.

And when we have a signal on a wire or cable in the hundreds of MHz or above, we now routinely use the term "RF" to describe its attributes, even though the signal is confined to a physical conductor, rather than air or vacuum medium. Yes, it's RF, but is it radio?

What about infrared (IR)? Those ubiquitous remote controls are definitely wireless, but they operate well beyond the conventional RF bands, and they observe the same Maxwell's equations which conventional radio links must follow. Yet, when engineers speak of RF or wireless, they usually don't mean IR–but I suppose they could.

The lesson here is not so much to "watch your language" and try to be more precise. That's not going to happen, nor is it necessary in most cases. But notice that I said "in most cases": there will be times you'll want to make your definitions clear up front, to avoid misunderstandings and even embarrassment among participants! ♦