'HF DDS as an UHF weak signal source (alias calculator) CLS PRINT : PRINT : PRINT PRINT " DDS alias calculator by S57UUU" PRINT : PRINT INPUT "enter clock frequency ", fc INPUT "enter desired output frequency ", fd n = INT(fd / fc) fs = fd - n * fc PRINT PRINT "We will use alias "; IF fs < fc / 2 THEN PRINT n; "+" fp = fs ELSE PRINT n + 1; "-" fp = fc - fs END IF PRINT : PRINT "Frequency that has to be programmed into DDS is "; fp IF fp < fc / 20 THEN PRINT : PRINT "WARNING! Frequency close to a dip - consider using a different clock frequency!" IF fp > fc / 2 - fc / 20 THEN PRINT : PRINT "WARNING Frequency close to a peak - consider using a different clock frequency!" IF fs < fc / 2 THEN fsp = fd - 2 * fp fzg = fd + fc - 2 * fp ELSE fsp = fd - fc + 2 * fp fzg = fd + 2 * fp END IF PRINT PRINT "Closest undesired aliases:" PRINT fsp; ", "; fd - fsp; "below desired frequency" PRINT fzg; ", "; fzg - fd; "above desired frequency"