Most FPV equipment uses a standard set of frequency channels. In the battle to offer ever-better specifications, some manufacturers now provide access to a much wider area of the radio spectrum. These expanded channels should not be used!
This article applies to pilots in the United States. If you live elsewhere, check your local regulations. Keep in mind that “lettered” bands are simply a construct of manufacturers to group a set of frequencies together and don’t match up with the concept of a frequency band in the radio spectrum. If that’s a new concept to you, take a look at “Understanding the Radio Spectrum” section in our article on frequency management.
There has been a progression from 7- or 8-channel to 32-channel equipment, then Raceband came along and 40-channel equipment became the norm. Now, 72-channel equipment can access frequencies down to 5.3GHz. Isn’t it a good thing to have an expanded ability for more pilots flying at once? Unfortunately, this is not a good way to achieve it.
The radio spectrum is divided and allocated into bands so that different types of uses don’t interfere. It is not simply available for anyone to use as they see fit! It’s important that you know who else might be using the frequencies you are on, otherwise you risk harmful interference. This is a technical term for making a signal unusable. You might cause harmful interference, making others’ use of the spectrum difficult. You may also receive interference, causing your own video to drop out. This is much more likely to happen if you are operating outside of the bands specifically allocated for your use.
You must either use Part 15-certified equipment or have a license to operate a radio transmitter. Most FPV equipment isn’t certified, but the spectrum from 5650MHz to 5925MHz—commonly called the 5.8GHz band—is open for use to anyone with an Technician-class amateur radio (ham) license. There are many other bands available to licensed amateurs as well, with different restrictions and usage requirements. A Technician license is the easiest to obtain and only requires taking a simple test. We’ve written previously about getting your license, and we encourage all FPV pilots to do so.
All of the channels in “Boscam A”, “Boscam B”, “Immersion/Fat Shark”, and “Raceband” fall within the allocated 5.8GHz band. The “Boscam E” band has a few offensive channels: E4 and E8 are completely outside the allocation, making them illegal to use. E7 doesn’t allow for a signal with any bandwidth at all—in effect, it’s also illegal.
The newly defined “L” band, in addition to “U” and “o” bands, operating from 5.3–5.6GHz, fall entirely outside the frequency allocation. The “H” band does stay within 5.8GHz, but gets dangerously close to the high and low edges. High-power transmitters would cause issues for nearby users outside the band, and it offers almost no actual benefit over Raceband. In the end, none of these extra channels are truly useful.
Other People Use These Bands
Just because you check your goggles before you power up and see static doesn’t mean a channel is clear. Many types of radio transmissions won’t show up on video goggles, or an application might simply listen to the natural environment at a given frequency. Here’s a particularly relevant example: weather radar can pick up transmissions at 5.3GHz.
Your Antenna isn’t Designed for it
Antennas are tuned for a specific frequency. They work best at or near this frequency, and their ability to pick up signals outside of that often drops off sharply. They are designed to do this on purpose, so they reject unwanted signals from other bands and reduce interference. If you’re trying to use a signal outside the range your antenna is tuned for, there are some important adverse effects. On a receiver, there will be reduced reception. You’ll be more likely to get interference and lose your picture—especially from the frequencies your antenna is tuned for. For a transmitter, sending power into an unmatched antenna can reflect power back where it can build up as heat and damage the transmitter. The further you are from the antenna’s tuned frequency, the worse this problem will be.
Be a Good Neighbor!
If we abuse the radio spectrum, it may not continue to be available. It’s up to the FCC to decide how it gets used, and they can change their mind. For example, use of the 4mm band is evolving as the FCC reviews vehicle radar applications. The FCC can also regulate imports and require compliance for transmitters, making it much more difficult for us to obtain FPV equipment. The radio spectrum is a shared resource—an attitude of respect will keep it usable for everyone.