  Radio emission of the quiet Sun is considered to be due to thermal
bremsstrahlung emission of the hot solar atmosphere. The properties of the
quiet Sun in the microwave band have been well studied, and they can be well
described by the spectrum of bremsstrahlung emission. In the meter-wave and
decameter-wave bands, properties of the quiet Sun have rarely been studied due
to the instrumental limitations. In this work, we use the LOw Frequency ARray
(LOFAR) telescope to perform high quality interferometric imaging spectroscopy
observations of quiet Sun coronal emission at frequencies below 90~MHz. We
present the brightness temperature spectrum, and size of the Sun in the
frequency range of 20-80~MHz. We report on dark coronal regions with low
brightness temperature that persist with frequency. The brightness temperature
spectrum of the quiet Sun is discussed and compared with the bremsstrahlung
emission of a coronal model and previous quiet Sun observations.
