<Li> Very little infrastructure is required for long - distance two - way communications using shortwave radio . All one needs is a pair of transceivers , each with an antenna , and a source of energy ( such as a battery , a portable generator , or the electrical grid ) . This makes shortwave radio one of the most robust means of communications , which can be disrupted only by interference or bad ionospheric conditions . Modern digital transmission modes such as MFSK and Olivia are even more robust , allowing successful reception of signals well below the noise floor of a conventional receiver . </Li>
which mode is used for short wave broadcast service
MFSK Olivia