Portable door knob alarm
FIG. 1 is a perspective view of a portable door knob alarm showing my new design, with the broken lines showing for illustrative purposes only and forming no part of the claimed design; 
     FIG. 2 is a front view thereof; 
     FIG. 3 is a right side view thereof; 
     FIG. 4 is a back view thereof; 
     FIG. 5 is a bottom plan view thereof; 
     FIG. 6 is a top plan view thereof.