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Discussion in 'Radio and Wireless' started by Nisar-von-Voltenbräackter, May 23, 2018.

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  1. May 23, 2018 #1
    Nisar-von-Voltenbräackter

    Nisar-von-Voltenbräackter

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    May 23, 2018
    Hi group,

    I want to build a remote digital signalling device to use inside public buildings. All it's supposed to do were to trigger a remote LED and make it light up until reset. I understand the FCC has allotted public space that can be used by anyone. After a period of seconds, or less, it won't need to be used again anytime soon.

    Does anyone have any experience in this area or advice on how to select a channel frequency? I'm thinking of clocking in the trigger code in slow steps so that it isn't likely possible to produce any problematic interference.

    Range will be the question of what free public channel space reserves for anyone to use without license.
     
  2. May 23, 2018 #2
    davenn

    davenn Moderator

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    Sep 5, 2009
    315MHz, 433MHz, 2.4 GHz are 3 that come to mind. There are for relatively short range use and limited to around 10mW ( see specific rules for country you are in)

    there are already TX and RX module sets available

    https://www.futurlec.com/Radio-433MHZ.shtml
     
  3. May 23, 2018 #3
    KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    Various frequencies are designated as ISM (industry, science and medical) which are the ones likely to be legal for your application. Would a repurposed and slightly modified inexpensive wireless doorbell system work?
     
  4. May 23, 2018 #4
    Bluejets

    Bluejets

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    Oct 5, 2014
  5. May 23, 2018 #5
    kellys_eye

    kellys_eye

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    Jun 25, 2010
    This could be problematic given signal attenuation.

    What size building? What form of construction?

    You may need multiple antennas and/or signalling positions.

    Suggest you purchase a pair of PMR walkie talkies and see how well (if at all) they work in the areas you plan to use the signalling in. You can get PMR with digital calling so could even adapt them (on receive) to activate an external LED.
     
  6. May 23, 2018 #6
    KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    Last edited: May 23, 2018
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