Most video transmission equipment used for First Person View (FPV) flying requires a FCC amateur radio license (aka "ham license") to operate legally. There is definitely good reason for that requirement and getting the license is not an overly complicated process. Even so, many people balk at the licensing obligation and either avoid FPV flying or do so illegally.
An alternative to getting a ham license (at least for US citizens) is to use non-licensed equipment--that is, devices that meet the FCC requirements for use without a license. Most of the common RF-transmitting devices in your home fall under that umbrella. That's why you don't need a ham license to operate your wireless router, cordless phone or remote garage door opener.
There are currently a handful of FPV video transmitters (VTX) that qualify for unlicensed use. By virtue of their certification, these transmitters have relatively low power output. Less power equals less range. But how much power is enough? I decided to test one of these systems to see if license-free FPV flight is practical.
Tactic recently released a line of FPV gear that includes a camera, a 7" monitor with dual built-in 5.8GHz video receivers, and three 5.8GHz video transmitters. The VTX units are available in 25mW, 200mW, and 600mW models. It is the 25mW FPV-T1 ($45) that is license-free. The FPV-T1 is actually larger and heavier than the more powerful models. This, however, is a reflection of the plastic case that encloses the FPV-T1. The other units have a heatshrink casing. Even so, the FPV-T1 weighs less than 20 grams with the antenna.
There are 22 channel options within the 5.8GHz band for this VTX. The desired channel is selected by positioning a bank of five dip switches on the back of the unit. A chart in the manual illustrates the proper switch positions for each channel, so keep it handy.
One of the biggest factors that can determine the reception quality and range of a given set up is the antenna selection. The FPV-T1, like the Tactic FPV-RM1 receiver/monitor, includes a linear polarized whip antenna. While they work acceptably well, they are pretty much the bottom rung of the 5.8GHz FPV antenna ladder.
The antenna is attached to the VTX with a common RP-SMA connector. Some VTX manufacturers use standard SMA connectors, while others use the reverse polarity RP-SMA style. You can buy antennas with either connector type, as well as adapters to make the difference moot.
While it is technically possible to swap out the stock antenna for an alternate type, such as circularly-polarized models, doing so would void the FCC-certification. The certification only applies to the device in its box-stock form. So if license-free operation is your goal, you're stuck with the whip antenna on the FPV-T1.
Ground Testing the FPV-T1
Before putting the FPV-T1 in a flying model, I wanted to get some sort of baseline for the range that I could expect from it. I've never had range issues with my other VTXs, but they are all 600mW units. Going from 600mW to 25mW means that I would be transmitting with only 4% of the power that I'm used to.
My test set-up was very simple. I bent some sheet plastic into a rudimentary frame that could house the FPV-T1, a 3-cell LiPo battery, and a RunCam 2 action camera. The battery was used to power the VTX, while the RunCam2 provided a live video signal. The whole setup fit neatly on to one of my camera tripods.
For the most realistic conditions, I took the rig to my usual RC flying field for testing. I set the tripod at the very end of the runway, which provided a handy reference point. I then tuned the FPV-RM1 monitor to receive the video signal. With the monitor in hand, I walked in a straight path down the runway until the transmitted image became fuzzy. Yes, that's a subjective yardstick, but my goal was only to get a ballpark idea of the system's range
In addition to the monitor, I was also carrying my Big 5 GPS unit. This let me determine exactly how far away I was from the VTX at any given moment. A few trials had the video feed consistently turning soft at a distance of around 350 feet. While that distance seemed good enough for my park flyer models, I expected the range to improve once I sent the VTX skyward.
Flight Testing the FPV-T1
Once ground testing confirmed that I would get a reasonable range from the FPV-T1, my next step was to test the system in a flying model. I decided to use the Hobbyzone Sportsman S+ that I recently reviewed. I had already fabricated a mount to place a camera on top of the wing. Adding the VTX and battery was just a matter of placing a couple squares of self-adhesive Velcro for them to cling to.
Again, I used the RunCam 2 as my video source. This camera will be the subject of an upcoming review. As I noted with another new camera, the Foxeer Legend, the latest generation of action cameras seem to have much-improved latency in their video-out signal. This allows them to function as both the FPV video source and HD recorder on moderately fast aircraft.
I usually use goggles when flying FPV, but I went with the monitor this time. Using the monitor made it easy to switch between FPV and line-of-sight piloting. I also had a spotter to give me a hand. I was able to attach the FPV-RM1 to my tripod using the monitor's built-in ¼-20 threads. The 7" screen was quite easy to see while flying.
I flew the Sportsman S+ as I normally would, meaning "not very far away". First of all, it isn't a big model. It also has a geo-fence incorporated into the SAFE+ stability system, which keeps it from straying more than 650 feet away.
I had adequate video reception for most of the flight. It would often drop out as I neared the fringes of the geo-fence, but I usually had ample warning before the signal degraded too much. I also noted that there seemed to be a small dead spot that was well within the overall effective range of the system. However, the signal drop-outs were very short as the model passed through this zone. I don't think it would have been an issue even if I had been wearing goggles.
After a few flights using the FPV-T1 in the Sportsman S+, I concluded that I have several models in my fleet that are contenders for license-free FPV flying. They are large enough to carry the weight of the FPV components (less than 3 ounces with the FPV-T1 and Run Cam 2, with power tapped from the model's flight battery), yet small enough that I wouldn't normally fly beyond the range of the system.
I would hesitate to put the FPV-T1 in a speedy model. You may go from a strong video signal to a useless one before you can turn the model around to stay in range. In fact, the moderately fast Sportsman S+ is on the upper end of the speed range I would consider.
License to Experiment
After seeing how well this 25mW system performs, I suspect that my normal 600mW signal is overkill for the FPV flying I do.
One of the tenets of amateur radio is that you should only use the minimum transmitting power necessary for the task at hand. After seeing how well this 25mW system performs, I suspect that my normal 600mW signal is overkill for the FPV flying I do. I plan to experiment with lower power options and see if I still get adequate performance for my racing quad and larger fixed wing FPV platforms.
When I translated that same mindset to the FPV-T1, I began to wonder how much its range could be improved with alternate antennas. Since I do have a ham license, I wasn't concerned about voiding the FCC certification. I have completed one session of ground testing thus far. My preliminary results suggest that I can achieve a significant improvement in range. If that holds true, the FPV-T1 could provide a low-power VTX option for a significant portion of my FPV fleet.
The bottom line is that I think license-free FPV is a viable option for those who choose not to pursue a ham license. You will just have to work with the range limitations that these systems present. I can think of numerous moderate-performance multi-rotor and airplane models that could successfully use the FPV-T1 as the foundation for an FPV system. If, however, something like FPV quad racing is your goal, you should probably get the license.
I think it goes without saying that my results are specific only to the equipment I used and my local radio environment. There are numerous variables than can impact the performance of any given FPV system. Your results may vary based on the conditions in your area.
Even though license-free FPV is viable, I still encourage aspiring FPV pilots to seriously consider getting a ham license. The process of obtaining the license will help you to understand how these systems work and become better able to use them effectively. Having the license also gives you legal access to a much broader selection of equipment that you can tailor to your specific needs.