Block Bluetooth Signals but not Cell Phone?

Hey everyone, been trying to find an answer to this, and I remembered this forum from my pre-mac days and figured it would be a good place to ask this.

What I'm trying to do is enclose a bluetooth signal from a phone completely in a box, while allowing cell signal to get in.

Tin foil blocks cell phone reception entirely, so I was thinking of using a screen mesh like on windows.

Does anyone know of a material to block bluetooth's 2.4ghz, but not cell phone signal?

There would be a power cable going into the box as well as an ethernet cord.

Thanks!

Whats wrong with just turning bluetooth off?

Because I need it connected to something.

I'm going to have like 50 phones connected via bluetooth, but the problem is interference starts when around 10 phones aren ear each other

Would it be possible to use external antennas for the cell signal and enclose the phones in tin foil or something else that blocks everything?

Cowboy Shane said:

Would it be possible to use external antennas for the cell signal and enclose the phones in tin foil or something else that blocks everything?

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That was my plan, except they dont make external antennas for the phones im using. And I can't make my own because there is no external antenna jack.

you would need a narrowband freqency jammer, the problem is the fact that most jammers are illegal.

The box you are describing is a Faraday Cage

A faraday cage made out of mesh will let in signals with a wavelength smaller then the mesh size; however do to size accuracy, signal attenuation, differering cellphone frequencies and the close proximity of the cellphone frequency to the bluetooth frequency you will have a very hard time actually getting a faraday cage to only block one signal and not the other.

Your best option would probably to have a cellphone repeater located inside a faraday cage. I want to say you can build your own cell tower for about $1500. You might also be able to use ATTs femto cell thing if you can get internet inside your box via the ethernet cable.


Are you getting interference on bluetooth or interference on the cellular band? Also which cellular network are you using.

Im using MetroPCS, which is a CMDA network.

The cell phones are connected via bluetooth to a VoIP gateway, which is turn is connected to the internet. I can then send phone calls to the metropcs phone.

Having about 10 cell phones connected to 5 bluetooth gateways is fine, but anymore than that produces interference between the bluetooth signals.

I'm trying to build a shoebox sized box with 5 VoIP gateways and 10 cell phones, and stack them ontop of each other instead of spreading them around the house.

TheGreySpectre said:

Your best option would probably to have a cellphone repeater located inside a faraday cage. I want to say you can build your own cell tower for about $1500.

Click to expand...

You can build one much cheaper then that passively. All you need is 2 Cell antennas, one outside the cage wired directly to one inside the cage. I must admit though, I dunno if this will in fact work, but its been used (and I've even tried it) for GPS use indoors. Normally, the 2nd (indoor) antenna would be attached directly to the unit, since being passive, even with a heavily shielded cable, there will be lots of signal loss.

Mpegger said:

You can build one much cheaper then that passively. All you need is 2 Cell antennas, one outside the cage wired directly to one inside the cage. I must admit though, I dunno if this will in fact work, but its been used (and I've even tried it) for GPS use indoors. Normally, the 2nd (indoor) antenna would be attached directly to the unit, since being passive, even with a heavily shielded cable, there will be lots of signal loss.

Click to expand...

Kinda what I was thinking.

I don't think your going to have any luck finding a material that blocks one frequency but not the other, and if you did it would probably be crazy expensive.

I think a physical hardware mod would be your best bet. Attach your own antenna and whatnot.

edit
You should look into attaching a blue tooth antenna. The antenna for blue tooth is the same frequency as wifi, and you should be able to find a highly directional antenna that may help.

I've never actually built one myself, I was just going off the numbers they had for the homemade base station that was used at the DEFCON demo.

How about building a passive repeater using two antennas and some coaxial cable? One antenna outside, one inside, then i can wrap the whole thing in tin foil to block the bluetooth signals.

hitbyaprkedcar7 said:

How about building a passive repeater using two antennas and some coaxial cable? One antenna outside, one inside, then i can wrap the whole thing in tin foil to block the bluetooth signals.

Click to expand...

http://www.overclockers.com/forums/showpost.php?p=6645488&postcount=8

Duh, I knew i got the idea from somewhere haha I started googling it then came back here.

*slapsforehead*