On 10/7/21 3:01 PM, Roger Need via groups.io wrote:
On Thu, Oct 7, 2021 at 12:01 PM, msat wrote:
@Roger
I'm in the US. I may very well be wrong, but I don't think operating in the
ISM band is as restrictive as you state. I'll certainly look into it more
carefully to ensure I'm complying with all applicable laws. Thanks for your
concern.
I worked for a company that sold equipment containing 900 MHz transmitters and my team was responsible for the design, testing and regulatory approval. We sold to may countries in the world and the United States FCC requirements were the most detailed and stringent of all of them. Everything we sold commercially had to be tested by independent labs and the report sent to the FCC for approval and issuance of an FCC ID# prior to sale. The purchaser however was able to use the devices without a license.
The only legal way to transmit on this band is:
- by purchasing a device which has gone through the approval process above. described in FCC part 15.
- to be a manufacturer developing a product using good engineering practices to keep radiation to a minimum.
- to construct home-built experimental device defined under 47 CFR 15.23 and constructed with good engineering practice and Part 15 emission limits
- to be a licensed amateur radio operator using commercial or home-built equipment operating according to power and out-of-band emission limits.
- an approved ISM (industrial, scientific or medical) non-intentional radiator - FCC part 18.
Part 5 experimental license would be how I suspect most people wanting to do this as an R&D project would do it.? That lets you radiate what you need, at preapproved frequency ranges, with appropriate interference mitigation, and a "stop buzzer" phone number.
Part 5 is how a lot of antenna ranges are licensed as well as things like Open Air Test Sites (OATS) who are doing testing of new devices (after all, you don't know, going in, whether it will meet the limits).
People developing radars typically use Part 5 as well.? It's not unheard of to use the Part 5 filing (which is public) to reverse engineer a competitor's unit.
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Or, of course, the historical "if your detectable energy is contained within your property lines, and nobody complains" approach.? That's probably pretty common for university and other similar research labs.?? If you're building one of Chauvet's coffee can SARs for instance.
The power limits for the band from 902 to 928 MHz. are described in FCC part 15 for devices like key fobs, cordless phones, video links, data links etc. If you use a single carrier for transmission the transmitted power is very low. The regulation is 200 microvolts/meter at 3 meters which is under 1 milliwatt into a small antenna. If frequency hopping or spread spectrum is used the field strength/power level can be much higher.
In essence as a home builder you are restricted to 1 mW of CW transmit power for your project if you wish to follow the FCC regulations.
The FCC regulations are available online. A very readable condensed version is on the ARRL site.
