| Abstract :
||Most attention these days of digital communication encompasses wideband
techniques. However new small band techniques are generating new and unique
applications. Only a few watts of RF energy are needed to accomplish worldwide
communications. Many of the small band modes allow to use signals buried in noise.
Using these techniques, for example EME (Earth-Moon-Earth) communications can be
performed much easier. Hardware and RF power are minimised. Digital modem
techniques using DSP are maximally used.
PSK31 allows real time chat modes but even pictures can be sent. Long distance
communication and controlled systems with mobile equipment are now much easier and
opens new possibilities for example in long distance, network independent and security
The aim of this work is to study these small band modes and look into the
boundaries of feasible applications. A controlled digital link has been set up using
mainly PSK31. Under these controlled conditions, phenomena such as noise,
interference, Doppler effects, SNR, IMD and BER are studied and measured. The
transceivers also can be used on antenna and work on 14MHz, a frequency where many
users can be found. This facilitates real life experiments.
One of the big problems when faced with slow modes is the lack of dedicated
instrumentation. Much practical information on small band modes is available from
radio amateurs, but there is little technical documentation. PSK31 is quickly becoming
one of the favourite communication modes.