Public Signaling

[Nisar-von-Voltenbräackter]

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.

 

[davenn]

Range will be the question of what free public channel space reserves for anyone to use without license.

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

 

[KJ6EAD]

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?

 

[Bluejets]

For 433mhz these seem to work ok.

https://www.ebay.com.au/itm/1CH-Rel...hash=item3d4ae1456d:m:mzKwQ-TcSX_7K_1jt9EVwwQ

variety of modes so you could press for activate and press again for reset.

 

[kellys_eye]

inside public buildings

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.

 

[KJ6EAD]

PMR isn't a thing in the US. Here the comparable UHF allocations are FRS or GMRS. We also have MURS in the VHF spectrum and LMRS in both VHF and UHF.

If you're interested in buying rather than building, GAMA makes and sells RF remote control systems at reasonable prices.

https://www.gamainc.com/product-cat...MI8PaImNOc2wIVgoKzCh1QrwQdEAAYASADEgIEvvD_BwE