Lessons learnt regarding interferometer yesterday!
Interferometers need hardware bias tees for SAWBird H+ 1420MHz filters with cascaded amplifiers, (which they also need as AD8302 chip requires certain level power input on SMA connectors to work) as no direct connection to power from USB.
The SAWBirds do not work if I forget to add bias tees into circuit- what an idiot I am!
Andy