If I’m in a populated area with stuff going in the 2.4 GHz and 5 GHz bands because of WiFi and other activity, are there any other choices for wireless communication between devices without pissing off the FCC?
Looking at the US spectrum allocation, it looks like there are a few other “amateur” bands, but the only ready-made radios that I know are based off 802.15.4, like ZigBee – which can operate at either 900MHz or 2.4 GHz. 900 seems like a possibility, but I thought that older cordless phones (the kind in your house, not cell phones) and microwave ovens sometimes use that band. Are there any other commonly use bands/devices for this sort of stuff?
Sorry, I should’ve specified – was looking for bands that digital devices could use to talk to one another without interfering with human conversations. CB is what truckers use, right? If a modem broadcasted on that, wouldn’t it annoy everyone with a CB radio?
Why do you care? I think the amateur allocation at 2.4 GHz is primary, meaning if you interfere with someone else’s Part 15 device, from the FCC’s point of view that’s their problem, not yours. Er…unless you’re talking about operating in an amateur band without a license. That would be naughty. And the FCC would indeed be cross, if someone told them about you. Which someone might well do.
I didn’t know you needed a license to use the amateur bands… I thought they were unregulated. My bad.
It’s not that I want to do anything nefarious, but the 2.4 GHz band seems pretty noisy, and I was hoping there’d be a cleaner part of the spectrum that could be used with low-power devices without interference to and from WiFi.
I see. Well, it depends on your purpose. If you want to communicate over a serious distance, e.g. a kilometer or so, then you will have to either get a license or use a commercial device that’s certified for one of the public bands, e.g. FRS, R/C, CB. It might be also possible to build such a device yourself, but I would guess if you don’t do it right the FCC has the authority to fine you for being an engineering putz. You can also build a low-power unlicensed (Part 15) transmitter, which should work within your backyard and house, just like WiFi itself. Again, there are FCC rules about that, which you can find by googling “Part 15 homebuilt transmitter” or something like that. I think it’s along the same lines, if you build something obnoxious and the FCC finds out your engineering was stupid they can fine you.
If you’re clever enough to build your own R/C setup, you can easily get an amateur license, by the way. Google “amateur radio license VEC” to find an exam spot near you. There are loads of good books to prepare.
Bluetooth LE is probably the way to go. I can get 400’ in free-air, and 75’ or better indoors.
I’ve also used some SiLabs EZ-raido chips that have enormous range (miles), and are in the 900MHz band, but they are not FCC pre-approved (but, that’s OK if you are just experimenting). They require designing your own PCB, though.
I use these devices on my quadcopter. The can run at 915 or 433 MHz. Both are fairly clean compared to the crowded 2.4 GHz band. I believe that 433 MHz technically needs an amateur license to operate in, but practice it’s pretty unlikely you’d get in trouble.