How to calculate signal loss when using a combiner?

[Mark22]

1-Please need help to figure out how to calculate the loss when using a 2-way combiner (diplexer). Assuming that I have two leads that I want to combine; OTA signal 14 dB and satellite signal 24 dB; the loss would be -4 dB. From which number I subtract 4, from 14 or from 24?
2-Also, it is absolutely necessary to have the signals to be combined of the same level (or very close; how close?) or they can be like in my example (14, 24)?
3-If they have to have the same level, how I do that?

Thank you

Mark

 

[gpenzenik]

If the insertion loss is -4dB then each signal is attenuated by the same amount.
14 - 4 = 10
24 - 4 =20
Signal matching depends on the application.
If you do need to attenuate the signal you use an inline attenuator.