  In order to allow for a comparison with the measurements from other antenna
systems, the voltage power spectral density measured by the Radio and Plasma
waves receiver (RPW) on board Solar Orbiter needs to be converted into physical
quantities that depend on the intrinsic properties of the radiation itself.The
main goal of this study is to perform a calibration of the RPW dipole antenna
system that allows for the conversion of the voltage power spectral density
measured at the receiver's input into the incoming flux density. We used space
observations from the Thermal Noise Receiver (TNR) and the High Frequency
Receiver (HFR) to perform the calibration of the RPW dipole antenna system.
Observations of type III bursts by the Wind spacecraft are used to obtain a
reference radio flux density for cross-calibrating the RPW dipole antennas. The
analysis of a large sample of HFR observations (over about ten months), carried
out jointly with an analysis of TNR-HFR data and prior to the antennas'
deployment, allowed us to estimate the reference system noise of the TNR-HFR
receivers. We obtained the effective length of the RPW dipoles and the
reference system noise of TNR-HFR in space, where the antennas and
pre-amplifiers are embedded in the solar wind plasma. The obtained $l_{eff}$
values are in agreement with the simulation and measurements performed on the
ground. By investigating the radio flux intensities of 35 type III bursts
simultaneously observed by Solar Orbiter and Wind, we found that while the
scaling of the decay time as a function of the frequency is the same for the
Waves and RPW instruments, their median values are higher for the former. This
provides the first observational evidence that Type III radio waves still
undergo density scattering, even when they propagate from the source, in a
medium with a plasma frequency that is well below their own emission frequency.
