|Waterfall without water.|
In CW and SSB a good operator can distinguish calls from the beep zoo. In digimodes the interpretation of the sounds is done by the computer, which makes the situation extra difficult: the QRM tolerance is very limited. In CW operation there is a common practice, when the frequency is getting warm: the pileup master starts telling "UP"...all CW operators don't understand this English word (sigh), but anyway, it's quite a good practice: people are calling the target station above the stations frequency, and the pileup operator picks the signals from the spectrum...this is a fair deal also for QRP operators: they get a real chance.
What to do on the PSK bands? When I want to work an interesting station, which are in a QSO (or trying to find one, in the hopeless zoo) I often try to call him a little bit besides his frecuency. Only very seldom the operator at the other end gets my idea! Why? Isn't this a good practice: find the nearest free frequency for putting a call? The QSO then could continue on that new frequency...why not? Isn't it quite convenient to pick traces in the waterfall display, especially with a comfortable mouse?
Another thing: PSK stations who know they are pileup targets, could select the calling frequency at the higher end of the band and say "UP1" to others...this is a common practice with RTTY.