We have investigated a Josephson effect heterodyne mixer for the millimeter wave band employing highhyphen;TcGdBaCuO point contacts. Mixer performance was in qualitative agreement with theory. A mixing response was observed up to 55 K, the highest operating temperature achieved for such a device to date. The voltage separation of rfhyphen;induced steps gave a value ofh/2e=2.08times;10minus;15Vthinsp;s which is in excellent agreement with the value expected for Cooper pairs. In addition, the temperature dependence of theI0Rproduct was found to agree with Bardeenndash;Cooperndash;Schrieffer theory in the weak coupling limit.
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