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Something like the CC2510 would be able to do what you're describing. There's a mini dev kit that comes with 2 dev boards and a programmer for $75 (http://www.ti.com/tool/cc2510dk-mini). There's also a smaller USB enable version (http://www.ti.com/tool/cc2511usb_refdes). These work at 2.4Ghz and would easily do 50' outdoors and 50' in most indoor situations. 

As far as the pairing - would they need to be unpaired and re-paired by the user; or would they simply be paired once in production and remain as matched pair? Either way you could dedicate different channels to each pair so they won't interfere with each other. 

Hi Chad,

Thanks, that board looks very good. I guess what I'm asking is how do two RX/TX pairs get separated - by using different frequencies (like GMRS radios) or by some sort of pre-shared code while transmitting in the same frequency? If it's the latter, then if two TX/RX pairs were paired at the factory, they should be able to co-exist in the same room and work independently of each other, and no further re-pairing work would be required?

Arty

The pairing scheme would depend on your design - if you use an existing protocol like ZigBee, blue tooth, SimpliciTI, etc., then you'll have to use what they provide (sorry I'm not familiar with those). If you don't use an existing protocol, you can do pretty much anything you can imagine. I've designed wireless smoke alarms that use a shared code while transmitting on the same frequency. Dozens of independent networks can work in the same room (or neighborhood in my case). This shared code could be pre-shared from the factory, or determined by entering a special pairing mode, or a combination of both (pre-share a code from the factory so everything just works out of the box, but give the option to un-pair and re-pair by entering a special mode). 

When operating multiple systems on the same frequency, only 1 unit can be transmitting at a time. This isn't a problem for many systems - my smoke alarms can simply wait 1 second if needed if someone else is transmitting (plus the odds of 2 homes in radio range starting a fire simultaneously are pretty low...). However, if you NEED to be able to handle 2 units transmitting at the same instant, then you'd need to separate them by using different frequencies. 

If you separate by using different frequencies, you can have multiple systems transmitting at the same instant in time without interfering. This is a little more complicated to implement, but very do-able with the CC2510 chips. 

Basically it's up to you and what your system needs -

Thanks a lot for your help, Chad - I ordered the CC2510 board and will be testing it in the coming days.

Arty

Hi Chad,

I got the kit, and it says "Not for use in Japan". I guess they just didn't go through the Japanese FCC with this particular board, but what about the CC2510 and its 2.4GHz range - is there a way to verify that something built on top of CC2510 can be used there?

Arty

I don't know why the board says not for use in Japan - maybe someone from TI knows the reason...

I honestly haven't certified anything outside of the US / Canada, so I don't know about the exact regulations; but there is an application note here:

http://www.ti.com/lit/an/swra060/swra060.pdf, Section 12 discusses Japanese requirements. I don't fully understand the details of the parameters they describe; but my understanding is that this chip is supposed to be able to pass the Japanese requirements. The CC2510 transmits in the open band for Japan, so it should be OK.

You might also want to look into costs for getting certified in each region. My product with USA / Canadian testing and certification cost $5-10k. I'd guess around the same again for Europe and Japan.