Why is the signal amplitude low on the oscilloscope even though the impedance is matched?
Do not confuse power transfer with voltage transfer.

If the source is indeed 50 ohms, and your scope is set to 50 ohms, it becomes a voltage divider and what you see is half the voltage that you will see when the scope is set to high impedance.







simulate this circuit &ndash; Schematic created using CircuitLab

Power transfer has to do with the relationship between the currents and the voltage. If the load resistor is zero, the current is max but the voltage across the load is zero so no power is transferred. If the load resistor is infinite, the voltage is max but the current is zero, so again no power is transferred. When Load resistance = Source Resistance V*I is at it's maximum.



But scopes do not work on power, they work purely on voltage. (or arguably current)