Hello Dan,

Can it be that Bob's situation is better with respect to losses?

75 Ohms load in a 50 Ohms system gives reflection coefficient of
(75-50)/(75+50) = 0.2 (voltage or current reflection).

So the power loss in this transition = 0.2^2 = 0.04 (4%, 0.18 dB).

The absolute worst-case situation would be when you have a quarter
wave line between a 50 Ohms source and a 50 Ohms load. The 75 Ohms
quarter wave line with 50 Ohms load will show a real impedance of
75^2/50 = 112.5 Ohm. This results in a reflection coefficient of
0.38, hence a power loss of 0.15 (0.7 dB). Of course when the line is
0.5 lambda long, there will be no additional loss.

Best regards,

Wim