Just to say, the comment on the graphs that the VNA covers 50 MHz to 20 MHz, is obviously wrong. My 8720D covers 50 MHz to 20 GHz. I do have another couple of VNAs here that cover 10 MHz. I will do some more measurements, with a more suitable VNA when I have both splitters here and some time for something that's not a high priority. I am not yet writing off the possibility of using the power amp and one of these 16-way splitters, as I probably have enough bits in my junk box to do it; and my initial observations are that the isolation doesn't depend too much on the terminations on unused ports. Bob questioned the need for 16 ports. I counted up and I have 9 bits of test kit which take an external reference. So having 16 ports, while nearly double I need now, is not so grossly over the top. Dave