W9SCH '$Buzz Box" for relative receiver sensitivity testing. Coil form can be any convenient nonconducting material, but using a toroitbwhich is self+hielding-might significantly reduce the amount of signal that the device would radiate. Wire size not given and not critical; try #22 to #28. No spacing between turns or between the two coils was specified; try winding hoth coils close spaced. Experiment a hit with spacing between the two coils if necessary,
for best results. Do not shield the coils. a reduction drive on the variable capacitor will make tuning less critical, or place asmaller variable capacitor across it to act as a fine tuning control. Different coil and capacitor combinations will allow operation on other hands.