In 1995, E.R.A.C. introduced the UEK21 converter design which allowed anyone to have an inexpensive unit able to detect the
hydrogen line. Together with a
shortwave receiver to get the needed IF gain and frequency selection and a homemade
parabolic antenna, it is possible for, say, a Young Scientist of the Year Project to build a radio telescope. Very soon, this unit was used in Europe also for SETI research as well for
Project Argus from the SETI League. Listening to
Jupiter with the shortwave receiver needed for 21 cm, it is also possible to remove the UEK21 converter and use only the shortwave receiver connected to a simple
dipole. If the frequency selected is above 18 MHz, it is possible when conditions are right to listen through the
ionosphere. At lower frequencies, the ionosphere is opaque. Here, two targets are possible: the Sun with its
solar flares or Jupiter, which is also a very strong radio source, together with the moon
Io, which is a very powerful natural radio wave transmitter. When Jupiter, Io and the
Earth are aligned, it is possible to hear this radio source very clearly. ==References==