We have demonstrated a high power intermodulation measurement set-up capable of delivering 30 W in each of two fundamental tones. For closely spaced frequencies (< 35 MHz), the dynamic range of the measurement is limited by the nonlinear performance of the mixer in the front end of the HP71210C spectrum analyzer. A tunable TE011mode copper cavity was fabricated in which one of the endwalls could be adjusted shifting its resonant frequency between 5.7 and 6.6 GHz. Since the Q-value of this

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... is high, > 104, and its bandwidth is small, < 1 MHz, it can be used to attenuate the two fundamental tones relative to one of the harmonic tones, which greatly enhances the dynamic range of the measurement. This set-up can be used to measure the two-tone intermodulation distortion of any passive microwave device, e.g. a HTS filter, a connector, a cable, etc., over a frequency range of 5.9 to 6.4 GHz and a power range of 0.1 to 30 W. The third order intercept (TOI) of a prototype HTS filter measured at powers up to 30 W was +81.3 dBm. Both fundamental tones were then presented to the DUT and the output power levels were measured for the fundamental and harmonic frequencies by the spectrum Submitted for publication in the 53 ra ARFTG Conference Digest, March, Superconductivity Group for their support.