Question about BNC to RCA adapters?

If you plug in a "female BNC to male RCA" adapter into a piece of equipment with an RCA connector, do you have a 75 ohm connection ? Or, do you just make your BNC cable "mechanically compatible" with the RCA jack on your equipment ?
It just makes it mechanically compatible. It won't help whatever degree of impedance discontinuity (mismatch) is presented by the RCA jack on the component, and it will most likely add an additional discontinuity of its own.

-- Al
That's what I suspected. Thanks for your answer. Matt
What about the other way around? An RCA cable > BNC adapter > BNC input on the unit?
I am thinking of just getting one side of this digital cable terminated with BNC...
Hi Jason,

I would reterminate that end to BNC. If you were to use an RCA-to-BNC adapter, the adapter itself would undoubtedly introduce a significant impedance discontinuity. And the RCA plug would also, unless it is one of those that is specifically designed to have a 75 ohm characteristic impedance, such as some of the Canare's.

BNC's are specifically designed to have accurate characteristic impedance, and will have good performance at the high frequencies that are present in digital signals.

Also, the fact that the other end is RCA will not nullify a lot of the benefit of having a good impedance match at the BNC end. Having a good impedance match at one end will minimize the number of times that waveform reflections resulting from impedance discontinuities re-reflect back and forth from one end of the cable to the other, before decaying to insignificance.

Best regards,
-- Al