Help with radio waves

[mvaldezrubio]

So I am going to buy a havahart in ground fence for pets. I want to see if i can make the radio signal travel in a 2D plane. I was thinking of using foil to block off the directions that I do not want the wave to travel. Hopefully, this will make a "wall" so that if the receiver intercepts the "wall" the device will go off. Is this possible? Any help will be appreciated. Thank you.

 

[tgootee]

It's probably not really practical, the way you are imagining it. You can make the RF stronger in certain directions, e.g. horizontally. But a vertically-oriented antenna element will already do that, on its own. Do a search for "antenna pattern". To do anything more-specific, you would need to be able to either measure the RF field, or simulate it (e.g. with the free 4NEC2). Metallic objects will have effects (as will things like the height above the ground), but they might be much more difficult to predict than you might predict.

You have the in-ground fence, to make the device trigger. What else do you need, exactly?

Also, assume that we do not know how those systems work, or what components are located where.

 

[mvaldezrubio]

It's probably not really practical, the way you are imagining it. You can make the RF stronger in certain directions, e.g. horizontally. But a vertically-oriented antenna element will already do that, on its own. Do a search for "antenna pattern". To do anything more-specific, you would need to be able to either measure the RF field, or simulate it (e.g. with the free 4NEC2). Metallic objects will have effects (as will things like the height above the ground), but they might be much more difficult to predict than you might predict.

You have the in-ground fence, to make the device trigger. What else do you need, exactly?

Also, assume that we do not know how those systems work, or what components are located where.

So any metallic object will distort the field?
What I want is to make a field 24ft in length and 8ft in height. This field will turn on an alarm when all sensors goes through the field arranged in a spherical figure. I was thinking that this havahart system could do the job if I modify it.

 

[davenn]

So any metallic object will distort the field?
What I want is to make a field 24ft in length and 8ft in height. This field will turn on an alarm when all sensors goes through the field arranged in a spherical figure. I was thinking that this havahart system could do the job if I modify it.

radio signals dont operat like that
you cannot just make them cut off at a certain distance

Dave

 

[mvaldezrubio]

radio signals dont operat like that
you cannot just make them cut off at a certain distance

Dave

I know they do not operate like that I just want to make a receiver and transmitter. The problem is I want to make a transmitter that only covers an area of 24ft. by 8ft. So that when all my receivers pass by this area it would turn on a light.

 

[davenn]

The problem is I want to make a transmitter that only covers an area of 24ft. by 8ft.

and that's what Im telling you ... a radio signal doesnt just stop at a given distance like that
even a very low level signal can propagate kilometres with a clear path

Dave

 

[mvaldezrubio]

and that's what Im telling you ... a radio signal doesnt just stop at a given distance like that
even a very low level signal can propagate kilometres with a clear path

Dave

What about the frequency from a havahart in ground dog fence. Could I get more precise with this system?
Im sorry for the bother I am just new to radio waves and frequencies. I am trying to learn.

 

[FvM]

Talking about the underground fence system as radio wave device is misleading. It's using a low frequency (I guess several 10k up to 100k) magnetical loop. The trigger zone spreads omnidirectionally around the loop wire as long as the field isn't cancelled by a second wire of opposite current direction. A wide metal sheets or welded mesh can attenuate the field on one side, but it will also reduce the trigger zone on the "free" side. I don't think that the method will bring you far. You can check the effect of various shielding geometries in an AC magnetic simulation.

 

[davenn]

Hey FvM

reading the blurp on the sales page for that device ... (havahart in ground fence for pets)
it has nothing to do with radio, its an electric fence ... period.
it lightly zaps the animal

Dave

 

[FvM]

it has nothing to do with radio, its an electric fence

You didn't read thoroughly.

 

[mvaldezrubio]

Talking about the underground fence system as radio wave device is misleading. It's using a low frequency (I guess several 10k up to 100k) magnetical loop. The trigger zone spreads omnidirectionally around the loop wire as long as the field isn't cancelled by a second wire of opposite current direction. A wide metal sheets or welded mesh can attenuate the field on one side, but it will also reduce the trigger zone on the "free" side. I don't think that the method will bring you far. You can check the effect of various shielding geometries in an AC magnetic simulation.

Thank you very much for all the help. So if I put that wire in a either circular or oval tubing and shield it so it only has a vertical exit will this work to give me the results I want? The AC magnetic simulation is the a specific product I can buy off the shelf? Again thank you.

- - - Updated - - -

Thank you for the help. So if I use a low frequency and on the opposite side use some type of shielding, would that work?

 

[davenn]

Keep Pets in and Unwanted Small Animals Out
The Havahart Electric Fence Kit is perfect for containing your pets, and for training them to stay out of certain areas. The electric fence delivers a mild shock that won't hurt your pet while providing correction to teach them where the off-limit parts of the yard are. The same fence will also keep unwanted small animals out,

says NOTHING about being a radio transmitter device

 

[FvM]

You are looking for the wrong device. The keyword is "havahart underground fence".

**broken link removed**

 

[davenn]

thanks for that ... that filled in a few blanks

cheers
Dave