If you are thinking about getting into FPV or if you are already using FPV equipment and have not done so, I would suggest that you consider getting your amateur radio license. There are a number of reasons to do that other than the simple fact that if you don’t; you will almost certainly end up either operating a radio transmitter illegally, or really not enjoying FPV.
Now before you start writing your scathing comment about how you actually don’t need a license if you just do this or that or keep your power under such-and-such a level , or how even if you should have a license, the FCC is hardly going to beat down your door and arrest you, please read to the end. There’s a good deal of misinformation floating about the web.
Getting an amateur radio license will benefit you directly in a number of ways, and getting the license is really not difficult. There’s a simple, 35 question, multiple choice test you have to take and pass. That’s it. There is more information on how to do that at the end of this article.
One of the ways getting a license can help you is by giving you, in the process of studying for the test, the information you need to understand not only how FPV works, but the rules and regulations that govern the use of that equipment so that you can make intelligent decisions about what you need and what you want. It will also introduce you to the terms and definitions that make reading about transmitters and antennas difficult. If you don’t know the difference between dBm and a dBuV, or lhcp and an isotropic radiator, the amateur radio literature is a good place to find out.
The Handbook for Radio Amateurs, published by the American Radio Relay League, has the answer to almost any radio related question you may have.
The knowledge you gain while working toward your license will also be invaluable in determining whether the ad you read about any particular piece of equipment is to be trusted or if it is mostly hype, as you'll see below.
Beyond that, getting your license will introduce you to a whole new community of people who know a great deal about the radio part of radio control. They can be a huge resource when you have questions.
The RC community sprang from a melding of the amateur radio community and the model airplane community back in the late 30’s when an amateur named Walt Good and his brother Bill perfected a radio controlled system for their plane and won the 1939 model aircraft Nationals.
Things have changed a good deal since then. Back then, transmitters were huge, tubes were the order of the day, and batteries were like bricks. All transmissions had to be done on amateur frequencies, and you couldn’t really fly more than one plane at a time in the same location. The radio part of radio control was the new and exciting thing.
Today, the radio part of radio control is mostly taken for granted. Much of the reason for that is the development of new technologies that allow more people to share the airwaves without interfering with each other. The 2.4 GHz transmitter that controls your plane is not only computerized and bound to your receiver, but employs a Distributed Signal Spread Spectrum transmission type that makes it hard to interfere with it. It also makes it harder for the transmitter to interfere with other services.
How this all actually works is beyond the scope of this article, but the result is that the FCC has been willing to certify many of these devices under Part 15 of the FCC rules, and what that means to you is that you don’t have to have a license to use them.
Essentially, the FCC is saying that these devices have been tested enough that they are confident they pose a minimal threat in terms of interference to other devices, and so long as you don’t modify these devices in any way, you don’t need a license to use them.
Any certified device will have an FCC certification number on the device itself and will be listed in the FCC data base along with the test results submitted with the manufacturer’s application for certification. Those results will, among other things, tell you the output power of the transmitter, if you are interested.
FPV transmitters are relative newcomers to the RC community. Unfortunately, they share more in common with the radios from the 30’s and 40’s than they do with the FCC certified DSSS transmitters that control your planes in that they emit an analog signal that is easy to interfere with and which can cause interference just as easily. It is the same type of signal that was abandoned by broadcast TV in 2009 for newer digital standards.
Almost none of these devices are FCC certified.
And the 5.8 GHz band is shared with medical devices, emergency mobile communications equipment, and the Amateur Satellite Service.
Be aware that FCC certification was around long before FPV. This isn’t an attempt by government to suddenly step in and curtail your rights. This is part of a system set up years ago allow as many people as possible to enjoy using the radio spectrum without interfering with each other.
There are a few devices with very limited range that operate using Wi-Fi technology that are certified and there are a couple manufactured by Shenzhen under the FatShark brand in the 5.8 GHz band that are. I’m sure more will hit the market as time goes on, but for now there are very few.
If any intentional radiator is not FCC certified, you need a license to operate it. Period. Don’t be fooled by anyone who says something like, “If it’s under 25 mW, you don’t need a license.” Don’t be fooled by advertising that says CE certified – that’s Europe.
And here’s where having the knowledge you might gain by getting an amateur license comes in handy.
Part 15.249 of the FCC rules gives the allowable output for an unlicensed transmitter in the 5.8 GHz band, certified or not:
This is not the regulation for DSSS signals (which allows more power), but for the type of signal from a FPV transmitter. As you can see, even a FCC certified, unlicensed device may not produce more than 50 mV/meter in the 5.8 GHz band.
Well, what does that mean?
If you do the conversions necessary to get the 50 mV/m to milliwatts ERP, you get a whopping 0.45 mW. Less than half a milliwatt.
Don’t be fooled by manufacturers saying their gear puts out 25 mW and you don’t need a license!
FatShark advertises a transmitter that is FCC certified and rates it at 5 mW output in some places. That seems much higher than the 0.45 mW limit. How is that possible?
In other places, they show the output to be much less.
The actual test results in the FCC data base are much closer to the specification sheet:
So when you do the math, guess what? The 93.88 dBuV/m gives us 0.45 mW ERP output.
Don’t expect too much in the way of performance from 0.45mW. Line of sight in a football field is about it, unless you have a very souped-up receiving system. FatShark claims you can about double that using their (rather expensive) goggles.
The knowledge you can gain getting your amateur radio license can help you make sense of all the conflicting information from manufacturers and from the forums.
I’ve had my amateur “ticket” since the 80’s. I’ve talked to astronauts on the International Space Station, worked the world through amateur satellites, built equipment, and chatted with literally more people than I could keep track of. It’s a great hobby. But it also gave me a foundation for getting involved with radio controlled airplanes that has made things much easier.
All you need for FPV work is the entry level, Technician class license. It’s a 35 question, multiple choice test from a pool of questions that are available to look at the Volunteer Examiner site.
You could pass the test just by memorizing the answers to the nearly 400 questions in the pool. You won’t learn anything that way, though, and I don’t recommend it.
One way to get all the information you need to pass the Technician test is to visit the ARRL web site. The ARRL is the official organization of radio amateurs and was founded in 1914. If you want to get a study text, I suggest the either the ARRL Ham Radio License Manual or the ARRL Tech Q and A book. If you want the ultimate reference, the Handbook for Radio Amateurs is available also, but that’s not designed to help you get your license as much as the others.
There really isn’t any trick to this. All the information is readily available. Even the test questions are readily available. It’s easier if you get a group together and help each other through the material, but anyone can do it, even alone. If there is a local Amateur Radio Club in your area, that’s a terrific resource.
You can check for classes being held in your area on the ARRL site and even sign up for on-line classes.
Like all things – including RC – there is a vocabulary to learn. There are a very few formulas you need to memorize. There’s some high school math involved.
When you are ready, the ARRL site can help you find a Volunteer Examiner in your area who can administer the test. So can your local amateur club. There is a small fee (currently $15.00) to cover paperwork. Once you pass the test, the FCC will mail you your license and issue your call sign.
Once you get your ham license, not only will you be able to fly FPV legally with the most powerful equipment, but there will be a whole new community waiting to welcome you and help you out. It’s well worth the effort.