  $\textit{AIMS.}$ (1) To use Parker Solar Probe (PSP) data to test the
accepted theory that type-III radiation is produced by counter-streaming
Langmuir waves that coalesce to produce the electromagnetic wave at twice the
Langmuir frequency. (2) To use the new data obtained from the PSP to improve or
modify the model of type-III wave generation.
  $\textit{METHODS.}$ To obtain new properties of the Langmuir wave and its
harmonics, their phase velocities and density fluctuations were measured. If
the harmonic wave was electromagnetic, as in the accepted theory, these
quantities would not be measurable. However, in an electrostatic wave, they
would be measurable by the PSP instruments.
  $\textit{RESULTS.}$ The Langmuir wave and its harmonics at frequencies of
$n\omega_p$, where $\omega_p = 2\pi\times125$ kHz is the Langmuir frequency and
$n \in \{ 2, 3, 4, 5, 6, 7\}$, were measured in an active type-III event. The
lowest harmonics contained density fluctuations, so they were electrostatic
waves and not type-III emissions. This result was bolstered by measuring their
very slow phase velocities ($< 20,000$ km/sec) which are not those of a
type-III wave. Thus, the harmonic waves were not a result of the three-wave
interaction (as required by the accepted theory) but they were electrostatic
antenna waves produced by radiation of the Langmuir wave. As at least the first
harmonic wave evolved through density irregularities, its wave number decreased
and it became the electromagnetic wave that was the type-III radiation. It is
also found that there is no evidence for or against the conventional model for
generation of the type-III emissions.
