With the non-calibrated Spectrum Y scales of ezRA / GNU radio,, how can hardware performance be compared and changes evaluated ?

That is the plus for the SDR Sharp > IF Average Plug-in for SDR Sharp > H-Line 3D software sequence, because even if you don’t have an absolute power scale, everything in the processing is linear, which means that relative changes are easy to see. There’s nothing in the typical processing chain for radio astronomy that would suggest that it has hidden non-linearities that would make measurement suspect.  Many “real” observatories use GNU Radio-based toolchains, as does the SETI Institute for some of their experiments, because the DSP chains in GNU Radio are all well-tested, and they’re used by dozens of different domains of application, quite separate from science instrumentation. The very basic and fundamental DSP blocks that are used in a typical radio instrumentation application are very very thoroughly tested–because they’re used by SO many different types of applications.

Absolute power scales need to be routinely re-calibrated in real life anyway, even if your back-end application pretends that it can show you absolute power as delivered to the antenna input, because system behaviours change at fine scales over time and temperature.

Above is an edited version of post on SARA Mailing List by Marcus D. Leech 13/9/2025.