Anyone who has looked anywhere online – Youtube videos or just perusing online stores for model aircraft parts – has seen devices for sending video signals from a model aircraft.
Most of the ones I see are not legal and do not comply with FCC rules in the U.S.
Many, if not most, of the devices that advertise “500mw” or “800mw” or “1200mw” and so on, are not legal devices, as used by most FPV flyers.
You have two options to legally add video or telemetry signals to your quadcopter.
- Use a Part 15 “unlicensed” device that complies with FCC rules. Up to 1 watt is permitted for spread spectrum (Wi-Fi) devices only; much lower limits apply to analog TV transmitters as used by many FPV video links.
- Use a device intended for use by a licensed Amateur Radio operator. When used for model aircraft control, FCC rules restrict the transmitter link to 1 watt (any mode including analog TV is fine).
Within Part 15 there are two classes of devices of interest:
- Spread spectrum, permitted up to a maximum of 1 watt power out.
- Non spread spectrum, which may be limited to as little as 1 milliwatt power out.
Part 15 Rules
The Federal Communications Commission (FCC) establishes rules for use of the radio spectrum.
Titled 47 Code of Federal Regulations, Part 15 specifies allowable limits for low power devices, unintentional and intentional RF emitters and other operations.
For a Part 15 (no licensed required) device, the 1 watt limit refers to spread spectrum devices like WiFi operating in specific bands allocated for Part 15 usage. Some quadcopters send video over WiFi and can legally transmit up to 1 watt. When the Tx is connected to a “gain” antenna, the power is to be reduced proportional to the antenna gain figure (about 1 db less power for each 1 db of antenna gain in excess of 6 db antenna gain).
Many of the FPV TV transmitters are running analog TV signals (not spread spectrum) and are restricted to vastly lower power limits. Most of the analog devices sold exceed legal limits. Some even operate outside the Part 15 bands, which is clearly against Federal rules. The FCC has proposed a $2.8 million fine to Hobby King for selling numerous devices that violate FCC rules and regulations.
Most Part 15 devices operate (like Wi-Fi) in the 2.4 Ghz band, or the 5 Ghz “Unlicensed National Information Infrastructure” bands. Some telemetry data devices used by model aircraft enthusiasts operate in the 902-928 Mhz Part 15 band.
A frequency near 433 Mhz is allocated for low power unlicensed operations in Europe. This frequency is NOT LEGAL to use anywhere in the United States where it is allocated to the Amateur Radio Service. There are numerous devices on 433 Mhz now being sold in the U.S. for remote control functions that are not legal in the U.S.
Part 97 Amateur Radio
The second 1 watt power limit applies to Amateur Radio operators. If you have an amateur radio license you can legally run up to 1 watt (any mode of operation) specifically for the control of model aircraft. This is spelled out in FCC Part 97.215.
While ham radio operators may operate up to 1,500 w PEP, the actual wattage level depends on the license class, the band in use, the geographic location, and the purpose (97.215 limits power output for telecommand of model aircraft).
If you have a ham radio license you can run up to 1 watt for the purpose of remote control – without having to provide standard station identification and providing remote control of the transmitter (say to turn a video transmitter on the aircraft on and off remotely).
A amateur radio operator could run more than 1 watt for remote operations provided station identification is used and there is a way to control the transmitter remotely.
Amateur Radio operators have access to many radio bands that may be used for remote control links such as in the 420-450 Mhz band. The 902-928 and 2390-2450 have overlap with Part 15 bands (these bands are co-allocated to multiple radio services). Amateur radio operators also have access to 5650-5925 Mhz which partially overlaps with Part 15 allocations at 5150-5350 and 5470-5825 Ghz. Some (but not all) Part 15 5 Ghz devices might be able to be configured for use as Amateur Radio devices.
Most of the Wi-Fi devices are probably okay.
Many, may be most, of the analog TV transmitters violate FCC rules. There are tons of such devices advertised online.
If you have a ham radio license (I do), you can legally run these analog transmitters up to 1 watt. Thus you can purchase one of the “not legal Part 15” FPV transmitters and use it, if you have a ham radio license.
My interpretation is that hams can run more than 1 watt provided you use normal station callsign identification on the link and you can remotely control the transmitter on and off.
Hope that helps.