Preferably, {TAIL ~ the microwave radiation} is at {HEAD ~ a frequency} of from twenty to 3000 MHz 
Preferably , { TAIL ~ the microwave radiation } is at { HEAD ~ a frequency } of from twenty to 3000 MHz
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH