In these dual loop couplers, performance is optimized over customer specified frequency range, providing very precise coupling values and excellent unit-to-unit tracking. Air dielectric main lines provide the extremely low insertion loss required to handle high power levels. They are available for use over modest bandwidths anywhere in the 100 to 3000 MHz frequency range. Single units, which monitor only a single direction, are also available as the CE series. Microlab/FXR loop couplers are generally much smaller than quarter-wave couplers and have a shorter insertion length. They are constructed from standardized designs and employ stocked components. Uncompensated loop couplers exhibit a 6 dB per octave coupling variation, which is generally acceptable for most system applications.