- Materials & Industrial Technology
An Introduction to Solid Wheel Antennas
What Are Wheel Antennas?
Wheel antennas received their name for their round shape; some wheel antennas are made from a single solid disk, unlike the multiple loops of wire forming a circle that create halo antennas. Other big wheel antennas use three separate loops of wire connected with a coax with a phased harness. Turnstile antennas use two identical dipole antennas in a cross shape to provide the 360° coverage wheel antennas provide with only a single component. This article focuses on solid wheel antennas.
Wheel antennas are omnidirectional, radiating the signal evenly in all directions around the edge of the wheel. They usually have modest gain. This is in contrast to the high gain directional antennas have.
Wheel antennas can be vertically stacked in arrays fed with a phasing scheme to create vertically polarized radiation. Without this, the wheel antenna puts out omnidirectional horizontally polarized radio frequency. The actual signal of a single wheel antenna resembles a donut shape with poor signal transmission directly above and below the wheel antenna. Stacking wheel antennas is also a solution when putting out a signal at a high power level (greater than 100 watts).
Wheel antennas are essential when you want to monitor a frequency for signals from any direction. You’ll have better reception with a wheel antenna than you would several directional antennas pointed in a rough circle.
Wheel antennas can be used in addition to a high gain yagi antenna, or they can be used by themselves as an omnidirectional antenna.
900 MHz Wheel Antennas
The 900 MHz wheel antennas can be used in UAVs. You can connect them to your UAV with a coax or soldered to a circuit board with an SMA connector. One of the benefits of the wheel antenna is that it is more durable than a dipole antenna, since it won’t get caught in tree limbs or get damaged in a UAV crash.
The 900 MHz big wheel antenna can be used as a beacon for UHF RF applications. The 33 centimeter or 900 MHz band is also used in amateur radio. This frequency range was once used for cordless phones and walking talkies but now used for FM repeaters and CW.
The typical gain for the Kent Electronics wheel antenna shown here is 2 dBi. The coaxial connector must be placed on the side without letter to avoid shorting out the tuning stub. This antenna’s typical return loss is -20 decibels at 900 MHz, which falls to -10 dB at 915 MHz.
1290 MHz Wheel Antennas
The 1290 MHz frequency is part of the L-band. The 1240 to 1300 MHz frequency range is allocated to amateur radio users. The 1300 MHz range is also used in space research and satellite communications. The frequency range is allocated as well to aeronautical radio navigation in the US.
The 1290 MHz wheel antenna by Kent Electronics resonates at around 1300 MHz depending on the SMA connector used. The wheel antenna can be tuned to 1295 MHz using a 1 pf cap put on the SMA connector. Add more chip caps and it can be tuned to 1200 MHz or 1.2 GHz.
2400 MHz Wheel Antennas
The frequencies around 2400 MHz are allocated to industrial, scientific and medical usage. This frequency range gets used for cordless phones, Bluetooth receivers, baby monitors and garage door openers. The 2.4 GHz wheel antenna design is commonly used in wireless networks like satellite TV and closed circuit television systems. Some car alarms use this frequency for their internal sensors.
The Kent Electronics 2400 MHz wheel antenna shown here has a horizontal polarization with a typical gain of 2 dBi. Return loss is around -20 dB at 2,400 MHz. Putting the antenna in a radome reduces its frequency, so to put out 2.4 GHz when the wheel antenna is placed inside a plastic housing needs to be made to produce closer to 2,500 MHz. The coax connector has to go on the side without letter so that it doesn’t short the tuning stub.