The U-47 was the first condenser microphone that could switch between omnidirectional and cardioid patterns. Collinear arrays are high gain omnidirectional antennas. Many CubeSats use an omnidirectional monopole or dipole antenna built with commercial measuring tape. Each antenna in a DVOR uses an omnidirectional antenna. Many hearing aids now have both an omnidirectional and a directional microphone mode. The transmit antenna also issues an omnidirectional sample. An omnidirectional microphone amplifies sounds equally from all directions. All LORAN-C antennas are designed to radiate an omnidirectional pattern. A completely uniform omnidirectional antenna is not physically possible. Most external microphone designs are of either omnidirectional or noise-canceling type. The improvement compared with omnidirectional reception/transmission is known as the directivity of the array. A small single cylindrical ceramic transducer can achieve near perfect omnidirectional reception. Higher-gain omnidirectional antennas can also be built. Most older hearing aids have only an omnidirectional microphone. The result is an antenna pattern that is no longer omnidirectional.