  Radio observations from decimetric to submillimetric wavelengths are now a
basic tool for the investigation of comets. Spectroscopic observations allow us
i) to monitor the gas production rate of the comets, by directly observing the
water molecule, or by observing secondary products (e.g., the OH radical) or
minor species (e.g., HCN); ii) to investigate the chemical composition of
comets; iii) to probe the physical conditions of cometary atmospheres: kinetic
temperature and expansion velocity. Continuum observations probe large-size
dust particles and (for the largest objects) cometary nuclei. Comets are
classified from their orbital characteristics into two separate classes: i)
nearly-isotropic, mainly long-period comets and ii) ecliptic, short-period
comets, the so-called Jupiter-family comets. These two classes apparently come
from two different reservoirs, respectively the Oort cloud and the
trans-Neptunian scattered disc. Due to their different history and - possibly -
their different origin, they may have different chemical and physical
properties that are worth being investigated. The present article reviews the
contribution of radio observations to our knowledge of the Jupiter-family
comets (JFCs). The difficulty of such a study is the commonly low gas and dust
productions of these comets. Long-period, nearly-isotropic comets from the Oort
cloud are better known from Earth-based observations. On the other hand,
Jupiter-family comets are more easily accessed by space missions. However,
unique opportunities to observe Jupiter-family comets are offered when these
objects come by chance close to the Earth. About a dozen JFCs were successfully
observed by radio techniques up to now. No obvious evidence for different
properties between JFCs and other families of comets is found.
