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Let's say, hypothetically, that I design some product that uses radio communication. Maybe something like a wireless lock. Or a scanner that tells you if a tag is near (in range of a few feet). Or a homemade radio.

If I didn't tell anyone, I assume I could (perhaps illegally) use whichever frequencies I fancied. However, imagine I wanted to sell one of these products. Which frequencies would I be allowed to use? Does it depend on how far the radiation is designed to travel for the given application?

I am aware that the information regarding FCC frequency allocation and regulations is out there. However, I came here because I was a bit overwhelmed by the information I got from other sources. What frequencies can safely be used?

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  • \$\begingroup\$ It's not just a question of frequency, but also effective radiated power. There are several internationally allocated ISM Bands for unlicensed Industrual-Scientific-Medical use. Additionally, in the USA, FCC part 15 rules regulate unlicensed transmissions. Each frequency band has its own allowed power limit, and for ISM / FCC part 15 bands, the power limit is even lower. For the short distances you mention, this should be feasible. Lower power also means longer battery runtime. \$\endgroup\$ – MarkU Aug 3 '16 at 4:42
  • \$\begingroup\$ Also: just because your product is "unlicenced" does not necessarily mean that you can afford to skip EMC testing. Once your product is in the hands of customers, they can stick it next to their Wifi router or their pacemaker, and customer will expect that there will not be any interference. This is one barrier to releasing a commercial product. If you were thinking more like a Dick Smith / Ramsey / Heathkit hobby radio kit, assembled by the customer, then there's no EMC testing (though finished quality may be variable). But product would seem more amateur in that case. \$\endgroup\$ – MarkU Aug 3 '16 at 4:51
  • \$\begingroup\$ One final thought: as a ham radio operator, I can attest that it's very hazardous to cause TV interference to your neighbors whenever the Olympics or the World Cup are on. What the part 15 rules are really trying to do, is spell out a safe boundary where the power level is low enough that it's not likely to cause any harmful interference. This is what Bluetooth and Zigbee are built on - you might consider whether you can just use a ready-made BT / BTLE module, as proof of concept or production. This would definitely be easier than starting from scratch. \$\endgroup\$ – MarkU Aug 3 '16 at 5:00
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The most likely candidates are the ISM bands. Even WiFi and BlueTooth (and many other popular schemes) use the ISM bands. Particularly the 915 MHz, 2.45 GHz, and 5.8 GHz bands. Note that if you want to sell products, you must have type-approval from the government agencies of the countries where you want to do business even if you use "unlicensed" bands like the ISM bands.

Ref: https://en.wikipedia.org/wiki/ISM_band

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