Polycrystalline samples of YBa2Cu3O7 were studied by the microwave abs
orption technique at the low magnetic fields in the temperature range
from 5 to 80 K. The direct microwave absorption and the field modulate
d microwave absorption were measured at 77 K. Analysis of the microwav
e absorption curves indicates that the field penetration into the samp
le starts from the lowest values of applied magnetic field within the
whole temperature range.