Physics, Waves

I am wondering about Perpendicular Wave Forms


If I have a Wave Form Traveling HOrizontally Can I cancel it out or alter it with another Wave form projected Perpendicular to it



_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-/ ......
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-\........
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-/ .........
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-\........
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-/ ........
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-\.........


I took limited Highschool Physics, and My University Physics was focused on Semi Conductors, and lasers not Wave forms, so I have no knowledge on the subject,

If it is waves in a fluid or gas, yes it can be done. However if it is light or rf dont even spend the time.

don't even spend the time?

I am dealing with Microwaves, and radio Waves,

are you telling me not to spend time on it because nothing will happen... or that the physics behind it are extremly complicated

I have as long as I like to do this so if there is anyway to stop the waves using other waves then I will persue it

Are you looking for something like constructive or destructive interference of waves at the intersection?

i'm confused by your drawing, it looks like multiple digital signals being cancelled out by a vertical wave.

you mentioned standing waves:
here is an excellent reference for more information on them--it's very easy to read: http://hyperphysics.phy-astr.gsu.edu/hbase/waves/standw.html


standing waves are reflected off of a surface, that is, a wave travels a distance, gets reflected off of a surface, the surface reflected wave and the initial wave are IN PHASE, causing the wave to appear to be "standing" and it's amplitude to double.

also, it's pretty important to say if your waves are travelling in air, or in a vacuum, and if they're in air, what is the temperature of the air.

electromagnetic waves can travel in a vacuum, like space (this is why satellites can transmit where there's no air), sound waves require a medium, be it air, water, whatever, they need SOMETHING to move through.

if your waves were in AIR, and you intersected 1 horizontal sound wave with a perpendicular sound wave, you would ALTER the horizontal sound wave's properties. This is because sound waves (depending on their amplitude and frequency) move air.

electric waves generate their own perpendicular waves, called magnetic waves:

see here for this excellent JAVA applet:
http://micro.magnet.fsu.edu/primer/java/electromagnetic/


the thing with your drawing is you assume that there are multiple STACKED waves being intersected by 1 veritcal wave. I don't think this is a possible situation, waves just don't stack like that, especially if they are in phase like the way you drew them.

I strongly recommend you look around the Georgia Tech site i listed up there, it's the BEST ONLINE PHYSICS RESOURCE I have ever found, I wouldn't have passed college physics 1 and 2 without it (my chinese professor was more than a little hard to understand.)

hope it helps

bl

doc said:

Are you looking for something like constructive or destructive interference of waves at the intersection?

Click to expand...

the goal is either to block out the Waves completely or to boost them out of a frequency range

bluce ree said:

i'm confused by your drawing, it looks like multiple digital signals being cancelled out by a vertical wave.

Click to expand...

Sorry for the confusion but it is dificult to "draw" in a forum post

Horizontal wave is a Microwave, the vertical wave can be any type of wave that could be used to interfere with the Microwave

bluce ree said:

you mentioned standing waves:
here is an excellent reference for more information on them--it's very easy to read: http://hyperphysics.phy-astr.gsu.edu/hbase/waves/standw.html

Click to expand...

Thanks for the link I will check it out

bluce ree said:

it's pretty important to say if your waves are travelling in air, or in a vacuum, and if they're in air, what is the temperature of the air.

Click to expand...

The waves travel in Air, for the testing the Air Temp is between 15C and 30C, BUT ideally the Temp range will be from -40C to +40C, The Horizontal Wave already travels in this temperature Range, its the interfereing wave that I would like to have the ablity to work regaurdless of temp.



Thank you very much for the links, they should help a lot,

Since you're using microwaves, why not just use a microwave signal attenuator? I realize they're expensive, but their purpose is to block a certain range of signals, and they do it passively (not drawing ANY power.)


Ok, then, could you tell me EXACTLY how your experiement is going to be setup? Why type of device are you using to generate the waves? What material is your waveguide made out of? How big is it? What other specs can you give--and include everything you can think of. Why do you need such a wide temperature range? IS THIS FOR A COMMERCIAL PRODUCT?

please elaborate.


BL

bluce ree said:

Since you're using microwaves, why not just use a microwave signal attenuator? I realize they're expensive, but their purpose is to block a certain range of signals, and they do it passively (not drawing ANY power.)


Ok, then, could you tell me EXACTLY how your experiement is going to be setup? Why type of device are you using to generate the waves? What material is your waveguide made out of? How big is it? What other specs can you give--and include everything you can think of. Why do you need such a wide temperature range? IS THIS FOR A COMMERCIAL PRODUCT?

please elaborate.


BL

Click to expand...

I'm sorry I would rather not Elaborate to much more since the product is hopefully going to be comercial. and we are in early brainstorming stages.


but the Waves don't travel in a single direction, from the "wave generators" they travel in all directions like a spear, Ideally Iwish to contain the Waves in a "box" the box being probably a few 100 square meters

the range of the signal is about 180Mhz.

ok.....

ok, mr. vague.

your box must be made of metal if you want to use EM right? (how else could you send the electric part of the signal?) Your source is omni-directional.

Sorry, I really don't understand what you want to do. It sounds like radar jamming.

good luck anyway.

Its not Radar Jamming, though it is similar, the Box is a building,

ideally the goal is to set up a perimiter around the building and have the waves block or alter the signal leaving the building

I don't really care about the Waves going up, or down. just the waves on the horizontal they are the ones I wish to alter/stop

It sounds like you want to kill the loud fan sounds coming from your computer :x

100 square meters

is far more then a computer case

no, it sounds like you want to prevent WiFi 2.4ghz signals, or 5GHz signals or 900MHz, or Infrared network signals from being detected outside the building. The japanese are working on some special kind of wood that absorbs 2.4GHz. Check it out.

Let me see if I've got this correct: you want to stop signals from leaving a building, right? In that case, the best (possibly only) way of doing it is to turn the entire building into a Faraday cage -- basically, a large grounded metal box with no openings larger than the wavelength you want to stop.

Carnil said:

Let me see if I've got this correct: you want to stop signals from leaving a building, right? In that case, the best (possibly only) way of doing it is to turn the entire building into a Faraday cage -- basically, a large grounded metal box with no openings larger than the wavelength you want to stop.

Click to expand...

are you sure that is the only way, I understand that method but ofcourse it is not an option, and the waves are needed with in the building, so sending a signal back along the Waves to cancle them out is not an Option either

deRusett said:

are you sure that is the only way, I understand that method but ofcourse it is not an option, and the waves are needed with in the building, so sending a signal back along the Waves to cancle them out is not an Option either

Click to expand...

The cancelling wave need not be sent back along the original wave, it could be sent in the same drection as the wave. The real problem is that you're dealing with waves in a 360 degree radius emanating from a central point (or perhaps multiple points). Thus you can't simply line up waveforms.

One of the first questions has to be what your success conditions are. Do the waves have to be completely cancelled or is it enough to simply change them? For example. Supposing your goal to be changing WiFi waves as the leave the building. Do you want to cancel the waves so that a snooper on the outside can't detect and decode them? Do you want to alter them in order to prevent access to a network? And in the latter case are you worried about someone actively trying to break in or just someone leeching bandwidth? Your answers to thes and similar questions will determine what your options are. Trying to prevent decoding will be very difficult if the decoder is determined. Prevent net access is difficult if you are worried about detemined hackers, but easier if you're just trying to prevent casual leeching.

In any case, here's an idea, again I'll be assuming the WiFi scenario, but you can change the solution to suit your medium.

In theory, one ought to be able to set up two wave forms leaving a single point that will cancel each other only periodically. In other words, the waves are slightly out of phase so that they interfere with each other for a while, then not, then they do again, etc. Because wifi requires a certain amount of integrity in the signal and is relatively short range, just calculate the interference wave so that the amount of interference is tolerable within the building but becomes intolerable outside the building and stay intolerable until the signal is too weak for reception.

This isn't a perfect solution if your goal is some sort of absolute secrecy. But done properly it should prevent all but the most determined foes.

Because a complete faraday's cage isn't practical (and I don't think legal,) why not attempt a modified one--that is put all of your repeaters up against a shielded metal plate--giving them a 180degree by 180degree directional pattern.

because wifi signals tend to suck directly above or directly below the source (depending on the circuit) Lateral transmissions are the only thing you really have to worry about.

If it's an office environment, don't rule out the use of IR network bridges, for stationary (relatively little movement) workstations, it's VERY FAST, proven and pretty secure (tint your windows to block IR)

The only material that I know of which resonates at 2.4GHz is water. Perhaps it can be useful, perhaps not.

I strongly recommend you DO NOT USE DHCP--or if you do ONLY TO KNOWN MAC ADDRESSES--otherwise you'll be seeing some chalk marks outside your building.

Get yourself a good 2.4GHz SWR meter to measure signal strength outside of your building, no matter what you decide to do--While a faraday's cage is ideal, I think it may interfere with cell phones.

Yet another possiblity is to use directional transmitters, like the coffee can ones--they greatly reduce the spread spectrum of the signal (make it narrower) while increasing the gain (but you can lower the gain)

stragically placed, with shielded plates behind them--that may be a workable solution--though if someone's out in the parking lot with their own notebook + coffee can, aiming it at your window, I don't think you can stop them---that's where the KNOWN MAC ADDRESSES come into play.

I would first begin by assuming that WEP is completely insecure--don't rely on it for anything--and for god sakes, change your password from "admin" to something with letters & numbers---go out to your parking lot and write down the license plate numbers+letters of 3 vehicles-- use that as a password.

though it sounds rediculous, never underestimate the power of aluminum foil with reguards to reflecting microwaves. I haven't seen any experiments on them, nor do I know if aluminum foil will reflect 2.4GHz, but ****, it's worth atleast an experiment--considering how cheap it is. Lead is out of the question, so is concrete--the 2 main materials used in nuclear fuel storage. Honestly, this is a wide open field, and A LOT of research needs to be done.

WEP will keep out the average joe, perhaps aluminum will keep signals in your building--though look out for the windows.

looky here:
http://www.eccosorb.com/catalog/eccosorb/AN.asp



aluminum would be a very good idea, just remember THAT IT MUST BE TREATED AGAINST WEATHERING AND MOISTURE. YOu can laminate it or whatever.

I just remembered, that a microwave operates at 2.44GHz, This is because water resonates at 2.44GHz, what happens when you put aluminum foil into a microwave? It reflects the 2.44GHz and causes the microwave to catchfire--but anyway, it reflects the waves!!!--also we're dealing with maybe 100mW at most, while a microwave oven is about 100Watts, like a 100,000 times difference.

Give it a try, I think it might be a very good, and cheap answer.

You could create a magnetic field around your "building" that would alter/degrade the vector of the stray or outbound signals. Hopefully noone is trying to communicate with the outside legitimately because your roof top relays will be offset in their line-of-site calibrations if you plan on either solutions.

I like the idea of a perimeter run installation though. IPO time you say??? Well, the FCC wont like the subsequent interference with horizontally travelling national communications systems...

cant help here, sorry this is way over my head (grade 10 this year) but it sure is interesting(and educational) to watch the discussion.