The Effect of High-Altitude Nuclear Explosions on Radio Communication

It is known that considerable interference with long distance radio communication resulted from the explosion of the two 4-MT bombs at high altitude over Johnston Island in August, 1958. A study was made of the effects reported in unclassified literature with the object of finding which type of transmissions, if any, could still be relied upon under such conditions. The conclusion reached is that VHF links using meteorscatter or ionoscatter propagation would have escaped the severe blackouts experienced with LF, MF and HF transmissions. The positive disruption of such VHF links requires some 100 times more ionization than was produced by these bombs. To a lesser extent VLF transmissions would also have escaped a blackout-in this case it is estimated that some 10 times the ionization is required for a blackout. These conclusions refer to transmissions in which the midpoint of the path is less than, say, 1000 km from the explosion.