A 3dB attenuator for a 50-ohm system might be constructed in the "T" format:

^{simulate this circuit – Schematic created using CircuitLab}

If you measure either input port or output port, should be 150.48 ohms

A 3dB attenuator for a 50-ohm system might be constructed in the "T" format:

^{simulate this circuit – Schematic created using CircuitLab}

If you measure either input port or output port, should be 150.48 ohms. Try measuring resistance from input port's "hot" pin to output port's "hot" pin...should be near 17 ohms.