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The Agilent 778D coaxial dual directional coupler has a frequency range extending over four octaves from 100 MHz to 2 GHz. Although the coupling factor increases 6 dB/octave below 100 MHz, directivity remains above 36 dB. Thus, the coupler can be used below 100 MHz as well as above. The usefulness below 100 MHz is restricted only by the amount of signal source power and/or the sensitivity of the RF detector connected to the coupler. The unidirectional characteristic of the Agilent 778D dual directional coupler makes it an important tool in microwave measurement systems. The 778D has the property of inducing, in an auxiliary line, a contra-directional flow of power which is proportional to the power flowing in the main guide. This coupler may be used in the measurement of reflection coefficients or SWR over a very wide frequency range. The relatively constant coupling across several frequency bands and the stability of coupling with time make the 778D useful, also, as a wideband attenuator or for power monitoring applications. Specifications. Frequency range: 100 to 2000 MHz (usable below 100 MHz). Coupling Attenuation: nominal coupling above 450 MHz is 20 dB, nominal coupling above 450 MHz is 20 dB increasing with a slope of 0.006 dB/MHz for decreasing frequency. Coupling variation: ±1.5 dB from nominal. SWR: Primary Line <=1.1, Auxiliary Arms <=1.1. Maximum main line power: 50 W average, 500 W peak. Options available: 778D (Type N female output, Type N male input connectors). Option 011 (APC-7 output, Type N female input connectors). Option 012 (Type N male output, Type N female input connectors)
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