Specific details are given for double-tuning the Varian V-4333 probe for use in the following heteronuclear magnetic double resonance experiments: observe1H at 100 MHz; irradiate2H,19F, or31P; observe19F at 94 MHz; irradiate1H,2H, or31P. An inexpensive source of audiofrequency-noise is described which, in conjunction with the double-tuned probe and several commercially available components, constitutes the basis of a versatile heteronuclear-decoupler. Examples are given which illustrate the effectiveness of this decoupler. Double-tuning of the Varian V-4333 probe by introducing a second transmitter coil is also described.