can you direct radio waves in one direction? like a laser?

[cameron marical]

could you have radio waves only travelling in one direction? like a laser, just with radio waves? if so, how?

[swansont]

You can build a resonant cavity with a lossy window. Microwave amplification systems (masers) were built before lasers were; the issue with radio waves is that the cavity needs to be larger (i.e. meters instead of centimeters) and you need a gain medium that emits in the RF.

 

You can also get directionality with your system by using a parabolic dish as an antenna.

[cameron marical]

ya, thats what i was thinking, just have something like these dishes all in a little sphere almost and have them direct everything to one way.

[mooeypoo]

Aren't radio waves electromagnetic waves, like light waves are, only different frequencies? So basically, shouldn't we be able to just have a laser that transmits in lower frequencies and we get "directional" radio waves.

 

No?

[swansont]

Aren't radio waves electromagnetic waves, like light waves are, only different frequencies? So basically, shouldn't we be able to just have a laser that transmits in lower frequencies and we get "directional" radio waves.

 

No?

 

Yes. A Laser is a resonant cavity with a lossy window and a gain medium, as I mentioned earlier. A resonant cavity means you get waves of a particular phase, and the gain medium gives amplification by stimulated emission.

[moth]

you can also use an array of antennas to get a beam. wikipedia has lots of info under "phased array".

the square kilometer array telescope will use array antennas

http://www.skatelescope.org/pages/page_student.htm

this page has more info and an animation to illustrate how a phased array makes a beam.

http://www.radartutorial.eu/06.antennas/an14.en.html

[NATO]

I was interested in this as a form or laser that could be used for daytime night time lazed tag. The problem with all the lazer tag guns on today's market is that there are no standards regarding frequency, laser type, or receiver types. No two lazer gun brands are compatible. All paintball guns use the same Ammo, as do airsoft guns. But the only good laser tag guns available are either for military training, or commercially rented out in arenas. You can't own one yourself, and if you did, your buddy would have to buy the exact same model or else they'd be incompatible.

 

Looking at R/C cars, the controllers work on different frequencies, to prevent competator's remote controls from mixing signals. If these radio waves could be focused into a beam, the same standard technology, or a modified version of it, could be used in a lazer gun. If people could change the frequency if thier lazer tag rifle as easily as R/C enthusiasts change frequencies with thier remote control planes and cars, then it wouldn't matter what brand of lazer gun you buy. It would open a whole new recreational market. No more paint, no more CO2, or BBs, no more safety goggles, NO MORE PAIN. And lazers can travel incredible distances, if focused accurately. This means marksmanship can finally be attributed with recreational war games.

 

Paint ball and Airsoft can't do that.

 

Regardless to what technology is used for the lazer, so long as it can operate in daylight, the important thing is to set standards for the manufacturing of these toy rifles, so they can be used competatively.

 

It's an idea me and another Airsoft enthusiast came up with after a comment was made about how silly an Airsoft sniper rifle is: At a max of 500 FPS, the strongest Airsoft guns cannot operate beyond 100yrds. Besides, even at that, 500FPS is so strong and painful to be shot with, it's banned from most organized Airsoft tournaments. Lazer tag rifles don't shoot any projectiles, so they are 100% harmless, and don't leave used ammo slewn about the woods. And lasers travel incredibly far, so a lazer tag rifle would make a great sniper rifle. All those mil-sim geeks could actually simulate a war at more than 50 ft! Much more challenging if you ask me. But there is no market open for it yet. No one takes lazer tag seriously like they do paintball. Even though for the reason I just explained it is so much better. I can only assume that the technology must not be there for no one to have thought of this before me.

 

 

 

Also while thinking army, if a radio message could be focused into a beam, it could be beamed from location to location without worry of enemies listening in, or intercepting them, because the only way to intercept the message is to place your receiver directly in the path of the beam.

 

The Navy already has a sound wave laser. It focuses sound waves into a beam, allowing them to blow the ears off pirates and unwanted intruders without lethal force. These same sound lasers have seen service in crowd control during riots. They can broadcast messages at different decibel levels at any range, you can whisper in someone's ear from a mile away, or blast a siren and no one outside the path of the laser would hear a peep!

 

The Air Force had plans for a microwave laser to melt and destroy ICBMs in mid flight. Though I have not heard a word about that project in years.

 

There are lasers made from just about any form of wave out there. What I want to know is;

 

What would it take to make a compact radio wave laser?

 

What other types of waves have not been made into lasers yet?

[swansont]

Compact and radio wave is a problem. If you want directionality, you need a transmitter antenna or cavity that is comparable in size to the wavelength of the EM radiation.

 

X-rays are hard to make into a laser-like system, because the transitions are short-lived and population inversion is difficult. Very long waves haven't been done because of the size.

[Enthalpy]

Directed radiowaves need the antenna size of a radar or of a radioastronomy receiver. It gets worse with longer waves.

 

An "X ray" laser has been demonstrated... it's X in the sense that it uses a transition between nucleus' states. But the energy of this transition is ultraviolet. Sort of cheating.

 

Gamma lasing at 511keV is reported by using a positron beam impacting matter. Positron-negaton pair exist for some time and are said to lase. With a short pulse, some superradiance allegedly occurred. I suggested (as a message in a box on a forum, as usual) to sweep the impact spot at light speed (by steering the positron beam) to get a directional gamma emission, as pairs would be produced just where the propagating gamma pulse passes. Read no reaction up to now.