Antenna selection guide
[learn_more caption=”Getting Started”] FPV is something you do, not something you buy. – A. Greve
First, let me open by saying that FPV is not easy and requires time and effort for true success. However, those who put in the effort are rewarded with an exciting new hobby. Understanding your aircraft and FPV system is important to getting the most out of your FPV experience. If you are impatient, easily frustrated or discouraged, know that the keys to answering your questions can likely be found in this guide or our instructional videos. Truly successful FPV flying requires knowledge of all sorts of different systems including:
Wireless transmission systems
Standard DC circuits
Electric power systems
Luckily, if you already fly an RC airplane, three of those items are at least somewhat familiar. In this guide, I will try to cover all of them. So what exactly is FPV? FPV or first person video (or first person view, your choice) is a method of flying a model aircraft, helicopter or multicopter via an onboard video camera. It gives a different perspective of the flight of the model. The pilot now sees directly from the aircraft, instead of as a third party observer. Some pilots fly this way for the great aerial views. Some fly it because it feels more like actually flying a real airplane. And a select few (including myself) do it because it is a challenge to be conquered. It’s this third group that is generally the most successful in their ventures.
What is all that equipment?
Really, the FPV “gear” is little more than a wireless security system fitted to an airframe. Granted, there is much modification involved and quite a few extra “accessories” are available specifically for the purpose of FPV, but almost nothing is new technology. The cameras and transmitters are analog. The cameras are basic CCD cameras. The airframes are just typical flying models. The only new technologies out there are the autopilot systems and antenna trackers. We will get into these in the advanced section. So how does it work? It’s quite simple. Your onboard camera is connected to a video transmitter which transmits the video back to a receiver. The receiver decodes the signal and sends it to a viewer (whether goggles or a TV screen) where the pilot watches the flight in real time. [/learn_more]
[learn_more caption=”Choosing your airplane”] The first thing you need to do is choose an airframe. Your choice depends upon your goals. Do you want a good view? Do you want to feel like you are inside an airplane? Do you want to go really fast? Do you want to stay in the air for a long time? Do you want to hover around objects? You can’t get all of these in the same airframe. It is best to start with a fairly basic and slow airframe, perhaps one that is already familiar with you or that you already own. Durability might be a consideration as well. You will crash it… Everyone does occasionally.
By far the most popular airplane type is the pusher prop plane. This puts the propeller behind the camera giving an unhindered view of the world in front of you. Some pull their cameras back a bit to put their nose in view so it feels like they are inside the plane, other stick the camera right on the nose so there are no obstructions. Flying wings are a great example of a pusher ship. However a flying wing is perhaps the worst choice for a beginner due to control difficulty.
Having a prop out in front isn’t necessarily a bad thing. For some, seeing the spinning prop gives a more realistic feel to the plane. Also it may be necessary for flying powered gliders where the prop opens up and takes up much of the video screen. The third option is the twin motor. Twin motors tend to be powerful, stable pattern ships. They are not necessarily easy to fly, and thus I recommend these for more experienced pilots or as a second FPV ship.
Some common airframes:
Chimera Flying Wing
[learn_more caption=”Choosing your frequency”]Frequency selection is all about balancing antenna size with noise floor, distance, and penetration. There are 4 common frequencies to choose from:
910MHz offers the greatest range and penetration per mW used. However the antennas are quite large (6″ across for a cloverleaf). Another issue that 910MHz faces is noise floor. Many traffic signals and cell phone services are on the 900MHz band. 910MHz works well for long range flying from an open field out in the countryside.
1.2/1.3GHz Offers excellent range and penetration with consistently low noise floor. In general, this band offers consistent performance as well as long range and penetration. This is the most common frequency used for long range piloting. This band is getting very crowded by video pilots and also is known to have issues with certain Long Range radio systems.
2.3/2.4GHz Is a great balance between performance and antenna size. The antennas are very manageable and the signals travel very long distances. The issues with this band are that you cannot use 2.4GHz for aircraft control. Also, 2.4GHz may be harmed by WiFi devices and 2.3Ghz may be harmed by cell towers.
5.8GHz offers the smallest antennas and the greatest number of available channels. The equipment is so small that it can be used on mini and micro sized multirotors. 5.8GHz is the weakest band for range and penetration. However, 5.8GHz offers many channels and has no known problems with any other equipment.
[learn_more caption=”Antenna selection”]
The antenna is perhaps the most important part of your Video system, so choose it wisely. The first thing you need to determine is polarization type: circular or linear.
– Linear polarization is the most common type. The antennas are smaller then their circular counterparts. Linear antennas suffer from multipath fading effects which means that reflected signals can return to the receiver and scramble the video feed or completely cancel it in some cases. However, with high gain antennas linear is capable of the longest ranges. Also a receiver antenna with high F/B ratio (such as a BiQuad) will minimize multipathing effects.
– Circular polarization is the industry standard for video piloting. When using circular polarization on both ends, reflected signals enter the receiver at significantly lower strength than direct signals. This results in cleaner video as well as better penetration. Circular polarization is best when used with high frequencies (ie 5.8GHz) or where penetration is needed. When choosing a circularly polarized antenna video clarity is directly related to axial ratio, not gain. The higher the axial ratio, the better the signal will be.
The next thing to know is what antennas to buy and where to place them. For linear, the Vee on the transmitter and a BiQuad on the receiver offers serious long range capability, but is not recommended for beginners. However, experienced pilots will find this takes them well past the 20 mile mark.
Most pilots will find that circular polarization offers the best performance for their needs. A BlueBeam antenna set offers excellent all around performance and most pilots will find this is all they need. This is a great starting point for beginners. If longer range or penetration is needed, a simple change-out of the receiver antenna is all that is required.
Helical antennas are the next step from an omni antenna. They offer better range and penetration in the main beam but have sidelobes that allow you to fly in all directions in close. Helicals are high axial ratio, wide bandwidth antennas that are perhaps the most well-rounded receiver antenna.
One more step up from the Helical is the Crosshair or Pepperbox. These offer incredibly high penetration and range. The Crosshair is best for object penetration or use with an antenna tracker. The Pepperbox is the low altitude wanderer’s dream antenna. These are intermediate and advanced pilot’s antennas as they do not have sidelobes which limit the signal strength when flying behind them.