The Right Wheel Antenna for the Job
What Are the Benefits of Wheel Antennas?
Wheel antennas are omnidirectional, able to receive a signal from any direction barring directly above or below them. Wheel antennas made from a printed circuit board have a horizontal polarization, though as a transmitter gains height (like a launching UAV), it can put out a cross-polarized signal.
If you vertically stack wheel antennas five eighths of a wavelength apart, you’ll have even more gain and receive signals at a far greater degree from the horizon than the donut shape profile a single wheel antenna will receive.
Solid wheel antennas made from printed circuit boards have one major advantage over cloverleaf antennas – durability. The clover leaf antennas made from three or four closed loop antennas are prone to bending if hit, making them a poor choice for drones and other applications where they could be damaged. A flat solid wheel antenna has a smaller profile, too, since it can be taken down and put away. Purchasing a solid wheel antenna is far easier than trying to make a clover leaf antenna. Because of their flat profile, they also take up less space in a crowded antenna tower.
As the frequency range increases, the wavelength and thus the size of the wheel antenna goes down.
So which wheel antenna is the right one for the job?
900 MHz Wheel Antenna
The 900 MHz to 930 MHz frequency range is used by industrial, scientific, medical (ISTM) and local communications equipment from amateur radio operators to walkie talkies to some UAVs. 900 MHz wheel antennas are ideal for UAVs and beacons because they send the signal equally well in all directions, especially if the transmitter is moving.
These wheel antennas have an average gain of 2 dBi. They have a return loss of -20 decibels at 902 MHz and -10 dB at 915 MHz. These wheel antennas are designed to work on the 900 to 930 MHz band, also known as the 33 cm band.
These wheel antennas are often used for UAVs; the ideal configuration is mounting them at a horizontal position of each link. If they don’t fit inside of the UAV, they can be mounted flat to the UAV’s wing. They can radiate in the second and third harmonics, which can require filtering if it is transmitting. This issue can arise when you are using UAVs for photography, filming and land surveying. For these antennas, you can use standard 4” PVC tubing to create a radome.
1290 MHz Wheel Antenna
The 1290 MHz frequency is part of the L-band. Governments often use this frequency range for long range radar systems. However, this frequency range is also available to amateur radio operators, UAV users, other aeronautical applications and radio-location (beacons).
At 1290 MHz, they have an average gain of -20 dB. These antennas can be tuned with chip caps. One pf (picofarad) chip cap alters its frequency reception by 5 MHz. These antennas can be used to monitor 23 cm beacons, probes, scanners or as an input for spectrum analyzers.
For these antennas, you can use 3” PVC pipe pieces as a radome.
2.4 GHz Wheel Antenna
These 2.4 GHz wheel antennas have an average gain of 2 dBi. They have an average return loss of -20 decibels at 2425 MHz. One pf (picofarad) chip cap alters its frequency reception about 20 MHz. Putting these wheel antennas in a glass or plastic housing pulls down its frequency range, too.
These wheel antennas are often used as drone antennas and can be used for WLAN. A 2.4 GHz Yagi antenna, however, is the better choice if you want to send Wi-Fi signals.
These are the smallest practical wheel antennas available with most manufacturers. This size of antenna requires you to attach the coax connector to the side of the antenna unless you have a very short lead to attach it to the antenna’s hub.