SubscribeThere are two common types of Omni-directional antennas - Whip Antennas and Solid Radome Antennas, how do they compare?
Whip antennas are made from a flexible wire to form a small diameter, flexible dipole. The second type of Omni antenna is a larger rigid dipole. The TACO Muldipol is made from a rigid tube of larger diameter to form a dipole with better gain and performance. The whip antenna, while inconspicuous and flexible in nature, results in lower cost, lower gain and therefore reduced range for the RF signal. It has higher VSWR due to the thinness of the dipole and a common approach to reduce VSWR is to employ a tuning circuit at the base of the whip antenna. This reduces output power of the antenna and the level of the received signal by introducing additional attenuation in both receive and transmit directions. Gain of a VHF Muldipol element is approximately 1.5 dBi while a whip antenna tends to be 0 dBi.
An even bigger problem with the whip antenna is variation of the vertical pattern of the antenna as the flexible dipole bends under the load of the wind. As the dipole is bent by the wind, it causes the vertical beam width of the antenna to be reduced in the direction of the landing aircraft, which is normally flying into the wind. Large intermittent drops in gain are possible and more likely to occur as wind speed increases. High wind suggests inclement weather with an additional loss of signal from any antenna due to rain attenuation. The performance of a whip antenna is not as good as that of a rigid antenna under normal weather conditions and the performance is further reduced during inclement weather with high winds, when antenna performance is most critical.
The TACO D5000 Muldipol Antenna Series are rigid antennas, designed for ground-to-air civil
aviation applications to eliminate the adverse affects of the reduced performance of a flexible
whip antenna during inclement weather conditions. Refer to Figure 1 for our typical single
element Omni-directional Muldipol antenna. During fair weather conditions, our single element
VHF TACO Muldipol antenna, model D5076, will have as much as 1.5 dB more gain than an
equivalent VHF whip antenna. In severe weather conditions, the received signal level at the
aircraft antenna will remain relatively constant with a TACO Muldipol antenna. This is not the
case for a flexible whip antenna as it is bent back and forth by the wind.
