How can I make BlueTooth (2.4GHz) reception area narrow and controllable?

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There are some BlueTooth modules available on the market, like cheap HC-05 for 3 or 4 USD delivered.



This one mentioned has internal PCB antenna which I guess has a toroid-like radiation pattern (omnidirectional):



enter image description here



However I need this module to be receivable in the narrow area only. Like 5-10 square meters area between the module and the ground.



What can I do to make this possible?



  1. Put some metal case around?

  2. Cut off internal antenna, connect external directional antenna?

Any other thoughts?










share|improve this question



























    up vote
    1
    down vote

    favorite












    There are some BlueTooth modules available on the market, like cheap HC-05 for 3 or 4 USD delivered.



    This one mentioned has internal PCB antenna which I guess has a toroid-like radiation pattern (omnidirectional):



    enter image description here



    However I need this module to be receivable in the narrow area only. Like 5-10 square meters area between the module and the ground.



    What can I do to make this possible?



    1. Put some metal case around?

    2. Cut off internal antenna, connect external directional antenna?

    Any other thoughts?










    share|improve this question

























      up vote
      1
      down vote

      favorite









      up vote
      1
      down vote

      favorite











      There are some BlueTooth modules available on the market, like cheap HC-05 for 3 or 4 USD delivered.



      This one mentioned has internal PCB antenna which I guess has a toroid-like radiation pattern (omnidirectional):



      enter image description here



      However I need this module to be receivable in the narrow area only. Like 5-10 square meters area between the module and the ground.



      What can I do to make this possible?



      1. Put some metal case around?

      2. Cut off internal antenna, connect external directional antenna?

      Any other thoughts?










      share|improve this question















      There are some BlueTooth modules available on the market, like cheap HC-05 for 3 or 4 USD delivered.



      This one mentioned has internal PCB antenna which I guess has a toroid-like radiation pattern (omnidirectional):



      enter image description here



      However I need this module to be receivable in the narrow area only. Like 5-10 square meters area between the module and the ground.



      What can I do to make this possible?



      1. Put some metal case around?

      2. Cut off internal antenna, connect external directional antenna?

      Any other thoughts?







      antenna bluetooth pcb-antenna






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited 25 mins ago









      Michel Keijzers

      5,09462255




      5,09462255










      asked 36 mins ago









      Roman Matveev

      1,06811331




      1,06811331




















          3 Answers
          3






          active

          oldest

          votes

















          up vote
          2
          down vote













          Neither will work.



          If you build a metal case with a narrow opening, you'll have an even wider beam; the smaller the aperture, the larger the beam.



          It's practically impossible in this form factor to controlledly cut off the existing antenna, and still have something to attach an external antenna to.



          But even so: at 2.4 GHz, the ground you mention will work as an OK reflector, and hence, things will still work in the area "indirectly" illuminated by ground reflection.



          2.4 GHz devices (such as Bluetooth devices) have to be designed to work with multiple reflections, so it being impossible to limit the area if you're illuminating a wall or a piece of ground is a feature your device has to have.



          You could try to add so much attenuation to the antenna that the signal is really really weak, but since a reflection might have relatively little loss compared to the first couple of meters of free space loss, this won't work out, either.



          Long story short: you can't.






          share|improve this answer



























            up vote
            2
            down vote













            This is very likely, impossible.



            Even if you would attenuate the signal, it would all depend of the sensitivity and power of the other pair.



            While you might be able to reduce your signal and on a particular device it would be only visible for a certain distance, it would totally change with another device.



            If you do so for security reason, it would only take someone to have a sensitive bluetooth device, or directional antenna to get the signal.



            Also RF signal is quite unpredictable, it can be reflected off objects, absorbed or go through.



            The only plausible way to have a RF signal locked to a certain area would be to have a Faraday cage, for example painting the walls with a conductive paint.






            share|improve this answer



























              up vote
              1
              down vote













              RF reception is rarely "narrow and controllable" unless you create a hard obstacle for the RF signal.



              By a hard obstacle I mean, a metal box (Faraday cage) out of steel plates or fine metal wire mesh (like the is in the door of a microwave oven). Only that can completely block the reception.



              Putting a case around the transmitter will prevent it from working (if done correctly) or make reception bad (if there are some holes left).



              You'd think that a directional antenna would do the job, that's true if there are no reflections which there will always be unless you're in free space. In the real world you cannot avoid a connection over the reflected signals unless you apply RF absorbers to all the walls in the room.



              So in practice: this will never work as well as you want it to.






              share|improve this answer




















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                3 Answers
                3






                active

                oldest

                votes








                3 Answers
                3






                active

                oldest

                votes









                active

                oldest

                votes






                active

                oldest

                votes








                up vote
                2
                down vote













                Neither will work.



                If you build a metal case with a narrow opening, you'll have an even wider beam; the smaller the aperture, the larger the beam.



                It's practically impossible in this form factor to controlledly cut off the existing antenna, and still have something to attach an external antenna to.



                But even so: at 2.4 GHz, the ground you mention will work as an OK reflector, and hence, things will still work in the area "indirectly" illuminated by ground reflection.



                2.4 GHz devices (such as Bluetooth devices) have to be designed to work with multiple reflections, so it being impossible to limit the area if you're illuminating a wall or a piece of ground is a feature your device has to have.



                You could try to add so much attenuation to the antenna that the signal is really really weak, but since a reflection might have relatively little loss compared to the first couple of meters of free space loss, this won't work out, either.



                Long story short: you can't.






                share|improve this answer
























                  up vote
                  2
                  down vote













                  Neither will work.



                  If you build a metal case with a narrow opening, you'll have an even wider beam; the smaller the aperture, the larger the beam.



                  It's practically impossible in this form factor to controlledly cut off the existing antenna, and still have something to attach an external antenna to.



                  But even so: at 2.4 GHz, the ground you mention will work as an OK reflector, and hence, things will still work in the area "indirectly" illuminated by ground reflection.



                  2.4 GHz devices (such as Bluetooth devices) have to be designed to work with multiple reflections, so it being impossible to limit the area if you're illuminating a wall or a piece of ground is a feature your device has to have.



                  You could try to add so much attenuation to the antenna that the signal is really really weak, but since a reflection might have relatively little loss compared to the first couple of meters of free space loss, this won't work out, either.



                  Long story short: you can't.






                  share|improve this answer






















                    up vote
                    2
                    down vote










                    up vote
                    2
                    down vote









                    Neither will work.



                    If you build a metal case with a narrow opening, you'll have an even wider beam; the smaller the aperture, the larger the beam.



                    It's practically impossible in this form factor to controlledly cut off the existing antenna, and still have something to attach an external antenna to.



                    But even so: at 2.4 GHz, the ground you mention will work as an OK reflector, and hence, things will still work in the area "indirectly" illuminated by ground reflection.



                    2.4 GHz devices (such as Bluetooth devices) have to be designed to work with multiple reflections, so it being impossible to limit the area if you're illuminating a wall or a piece of ground is a feature your device has to have.



                    You could try to add so much attenuation to the antenna that the signal is really really weak, but since a reflection might have relatively little loss compared to the first couple of meters of free space loss, this won't work out, either.



                    Long story short: you can't.






                    share|improve this answer












                    Neither will work.



                    If you build a metal case with a narrow opening, you'll have an even wider beam; the smaller the aperture, the larger the beam.



                    It's practically impossible in this form factor to controlledly cut off the existing antenna, and still have something to attach an external antenna to.



                    But even so: at 2.4 GHz, the ground you mention will work as an OK reflector, and hence, things will still work in the area "indirectly" illuminated by ground reflection.



                    2.4 GHz devices (such as Bluetooth devices) have to be designed to work with multiple reflections, so it being impossible to limit the area if you're illuminating a wall or a piece of ground is a feature your device has to have.



                    You could try to add so much attenuation to the antenna that the signal is really really weak, but since a reflection might have relatively little loss compared to the first couple of meters of free space loss, this won't work out, either.



                    Long story short: you can't.







                    share|improve this answer












                    share|improve this answer



                    share|improve this answer










                    answered 19 mins ago









                    Marcus Müller

                    28.9k35389




                    28.9k35389






















                        up vote
                        2
                        down vote













                        This is very likely, impossible.



                        Even if you would attenuate the signal, it would all depend of the sensitivity and power of the other pair.



                        While you might be able to reduce your signal and on a particular device it would be only visible for a certain distance, it would totally change with another device.



                        If you do so for security reason, it would only take someone to have a sensitive bluetooth device, or directional antenna to get the signal.



                        Also RF signal is quite unpredictable, it can be reflected off objects, absorbed or go through.



                        The only plausible way to have a RF signal locked to a certain area would be to have a Faraday cage, for example painting the walls with a conductive paint.






                        share|improve this answer
























                          up vote
                          2
                          down vote













                          This is very likely, impossible.



                          Even if you would attenuate the signal, it would all depend of the sensitivity and power of the other pair.



                          While you might be able to reduce your signal and on a particular device it would be only visible for a certain distance, it would totally change with another device.



                          If you do so for security reason, it would only take someone to have a sensitive bluetooth device, or directional antenna to get the signal.



                          Also RF signal is quite unpredictable, it can be reflected off objects, absorbed or go through.



                          The only plausible way to have a RF signal locked to a certain area would be to have a Faraday cage, for example painting the walls with a conductive paint.






                          share|improve this answer






















                            up vote
                            2
                            down vote










                            up vote
                            2
                            down vote









                            This is very likely, impossible.



                            Even if you would attenuate the signal, it would all depend of the sensitivity and power of the other pair.



                            While you might be able to reduce your signal and on a particular device it would be only visible for a certain distance, it would totally change with another device.



                            If you do so for security reason, it would only take someone to have a sensitive bluetooth device, or directional antenna to get the signal.



                            Also RF signal is quite unpredictable, it can be reflected off objects, absorbed or go through.



                            The only plausible way to have a RF signal locked to a certain area would be to have a Faraday cage, for example painting the walls with a conductive paint.






                            share|improve this answer












                            This is very likely, impossible.



                            Even if you would attenuate the signal, it would all depend of the sensitivity and power of the other pair.



                            While you might be able to reduce your signal and on a particular device it would be only visible for a certain distance, it would totally change with another device.



                            If you do so for security reason, it would only take someone to have a sensitive bluetooth device, or directional antenna to get the signal.



                            Also RF signal is quite unpredictable, it can be reflected off objects, absorbed or go through.



                            The only plausible way to have a RF signal locked to a certain area would be to have a Faraday cage, for example painting the walls with a conductive paint.







                            share|improve this answer












                            share|improve this answer



                            share|improve this answer










                            answered 18 mins ago









                            Damien

                            1,006112




                            1,006112




















                                up vote
                                1
                                down vote













                                RF reception is rarely "narrow and controllable" unless you create a hard obstacle for the RF signal.



                                By a hard obstacle I mean, a metal box (Faraday cage) out of steel plates or fine metal wire mesh (like the is in the door of a microwave oven). Only that can completely block the reception.



                                Putting a case around the transmitter will prevent it from working (if done correctly) or make reception bad (if there are some holes left).



                                You'd think that a directional antenna would do the job, that's true if there are no reflections which there will always be unless you're in free space. In the real world you cannot avoid a connection over the reflected signals unless you apply RF absorbers to all the walls in the room.



                                So in practice: this will never work as well as you want it to.






                                share|improve this answer
























                                  up vote
                                  1
                                  down vote













                                  RF reception is rarely "narrow and controllable" unless you create a hard obstacle for the RF signal.



                                  By a hard obstacle I mean, a metal box (Faraday cage) out of steel plates or fine metal wire mesh (like the is in the door of a microwave oven). Only that can completely block the reception.



                                  Putting a case around the transmitter will prevent it from working (if done correctly) or make reception bad (if there are some holes left).



                                  You'd think that a directional antenna would do the job, that's true if there are no reflections which there will always be unless you're in free space. In the real world you cannot avoid a connection over the reflected signals unless you apply RF absorbers to all the walls in the room.



                                  So in practice: this will never work as well as you want it to.






                                  share|improve this answer






















                                    up vote
                                    1
                                    down vote










                                    up vote
                                    1
                                    down vote









                                    RF reception is rarely "narrow and controllable" unless you create a hard obstacle for the RF signal.



                                    By a hard obstacle I mean, a metal box (Faraday cage) out of steel plates or fine metal wire mesh (like the is in the door of a microwave oven). Only that can completely block the reception.



                                    Putting a case around the transmitter will prevent it from working (if done correctly) or make reception bad (if there are some holes left).



                                    You'd think that a directional antenna would do the job, that's true if there are no reflections which there will always be unless you're in free space. In the real world you cannot avoid a connection over the reflected signals unless you apply RF absorbers to all the walls in the room.



                                    So in practice: this will never work as well as you want it to.






                                    share|improve this answer












                                    RF reception is rarely "narrow and controllable" unless you create a hard obstacle for the RF signal.



                                    By a hard obstacle I mean, a metal box (Faraday cage) out of steel plates or fine metal wire mesh (like the is in the door of a microwave oven). Only that can completely block the reception.



                                    Putting a case around the transmitter will prevent it from working (if done correctly) or make reception bad (if there are some holes left).



                                    You'd think that a directional antenna would do the job, that's true if there are no reflections which there will always be unless you're in free space. In the real world you cannot avoid a connection over the reflected signals unless you apply RF absorbers to all the walls in the room.



                                    So in practice: this will never work as well as you want it to.







                                    share|improve this answer












                                    share|improve this answer



                                    share|improve this answer










                                    answered 19 mins ago









                                    Bimpelrekkie

                                    44.1k23996




                                    44.1k23996



























                                         

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