Leasing the Sky: The Technology and Economics of Spectrum Sharing

So, interestingly, it turns out that a lot of people want to use the same interval of the spectrum.

Why can't we just simply move one of the signals somewhere else, like we do on our AM radio dial? We dial in different frequencies.

Why can't we just move it up or down the spectrum to different frequencies?

Well, that's a good question, Bob, and I think it's one that has been asked a lot.

The reason we can't do this, and you have to also wonder why does everybody like low and mid band frequencies? It turns out that the frequencies from anywhere just below a gigahertz to about four or five, maybe six gigahertz are in very high demand.

Last year in 2025, there was a big argument about the 3.1 to 3.45 gigahertz band and radar and wireless communications both wanted to use it.

Radar is a Department of War asset that uses that to be able to sense and detect.

So it's obviously very important.

But many wanted to auction that band off to commercial wireless to be able to bring income.

Now, why do they both want that band? Why can't we just use higher frequencies for one of them? The answer is, is that is actually a lot of people call it beachfront property.

It's very special frequency ranges because For example, the aspect size is small enough so radars really like this band because essentially your antenna can be made reasonably small and have an electrical length that is commensurate with the characteristics of something you'd want to detect.

Maybe it's an aircraft or a ship or whatever.

You can get a really good detection image of that ship or aircraft because of the small frequency.

If you go to lower frequencies, then the wavelength is longer.

And so you aren't able to get as good of an image because it turns out that whatever you're trying to sense actually has not as many wavelengths.

So as you get to a lower frequency, whatever you're detecting is not as many wavelengths and you're not able to get as good of an image.

The other thing is the size of transmission antennas and reception antennas is actually very reasonable.

In fact, the higher you go up because the antenna size is based on the wavelength, the smaller the circuit gets to build an antenna.

And you might ask, well, why don't we just keep going up, right? If detection is based on wavelength and antenna size is important, why don't we just keep going up? Well, then there's the other part of the trade-off.

And it turns out that we have atmospheric attenuation and also just propagation loss based on one over the distance squared for communications, one over the distance to the fourth for radar.

And it turns out, though, that the loss actually is based on the wavelength.

Just to clarify, wavelength is the same as the frequency.

So if you talk about different wavelengths, you're talking about different frequencies.

And the longer the wavelength is, the lower the frequency.

That's right.