What is the rationale for the 0 dBm voltage value in power source?

[ra3xdh]

Discussed in #778

^{Originally posted by csrabak June 22, 2024}
The magnitude of the voltage source for the Qucs-s power source, available in the components->sources pane puts 0.316228 V as magnitude for a 0 dBm power, 50 Ω (default impedance).

The line of the exported netlist is:

VP1 out 0 dc 0 ac 0.316228 SIN(0 0.316228 1MEG) portnum 1 z0 50

Since simulators use magnitude for this parameter, which is the peak voltage of the source, this value would be OK for an open circuit, but due the internal impedance only one fourth of a milliwatt is available to the matched load.

Shouldn't the voltage be such that when a matched (i.e. 50 Ω) load is fed the power delivered to the load be 0 dBm (1 mW)?

[tomhajjar]

I forgot to show the data from ngspice was different than Qucsator...

dBm_Voltage.zip

[tomhajjar]

Seems to be fixed in update I just got

[ra3xdh]

Yes, the Ngspice/Qucsator data mismatch was fixed by #780. The latest continuous build has this fix.