Tuning a diplexer can be difficult, but having all the right tools can make it easier. Now we show how using three R60 1-Port VNAs can measure all three ports of the diplexer at the same time. Doing this simplifies the tuning procedure which tends to be highly involved. Also, use of an affordable TR1300/1 2-port VNA or a 4-port Cobalt C1409 VNA would be useful for this application.