Same frequency. Different streams of information launched into the ether all on the same frequency. But the streams are oriented in space in a way they do not interfere with each other.
From: Cameron Crum Sent: Monday, May 22, 2017 9:03 AM To: [email protected] Subject: Re: [AFMUG] OAM How do you have different wavelengths and not different frequencies? Or are you referring to frequency as some channel of a certain bandwidth? On Mon, May 22, 2017 at 9:35 AM, Chuck McCown <[email protected]> wrote: I finally re-read an IEEE magazine enough times to understand the OAM propagation. (Orbital angular momentum) If you have missed it, for the past 20 years there have been thousands of white papers written on a type of radio signal called OAM. It looks a lot like circular polarization but the interesting thing is that you can use the same frequency for multiple streams that do not interfere. In theory an infinite number of streams. So, here is how I got it explained to myself so that I could understand it. Using a special antenna, each wave front is launched like a smoke ring. And the wave itself , or integer multiples of the wave are like little snippets of string formed into a ring. That is the smoke ring. As you traverse it around the ring the phase of the smoke changes. So think of it as taking a n-lambda foot long chunk of the radio signal. Chop it out like a long piece of baloney and join it to its self. Then set up some kind of launcher that can throw these rings of signal at the other end, not like a frisbee but like a pie in the face. Different numbers of wavelengths can be chopped out of the baloney and joined up as a ring. If you have rings from one transmitter made out of two wavelengths and rings from a different transmitter of three wavelengths, they can all use the same frequencies and they will not interfere with each other. The downside is you have to have some really complicated funky antennas at each end and they have to be aimed up perfectly. The antenna center must be in the center of the smoke ring to receive it properly. If it is off to the edge it will not have the clean separation from the other rings with different integer multiples. Should work for very high frequencies over short distances. Like 10 GHz on up. They are doing it with lasers. I have see the 10 GHz antennas. They look like the internal parts of a rotary snowplow.
