Be careful when using a T BNC connector. Some are just T connectors, others actually provide 50 Ohm termination.
In the first photo are a proper 50 Ohm T terminator, a regular T connector, and an end cap.
In the second you can see the proper 50 Ohm T terminator is producing a 4 Volt peak to peak signal (which is what was output at 50 Ohms from a signal generator) even though one end of the T is left open.
What happens if you terminate (read: connect anything with a proper 50 ohm impedance) to the other end of the T? If the answer is "it magically converters into a normal T", what is this sorcery? If the answer is "you shouldn't do that, it's already terminated just right", what is the point of it being in a T shape with a plug you can't do anything with?
RS, not sure if I understand your question.
The point I was trying to make in my post is that there are different types of T connectors/terminators. This was in response to recommendations in this thread for the OP to consider using a T as a 50 Ohm terminator.
The T in the second photo will provide a 50 Ohm termination using just one side of the T (with no need for a cap or a second channel or a second piece of equipment to be terminated); it will also provide a 50 Ohm termination if a second channel or a second piece of equipment is terminated on the second side of the T. This type of terminator offers flexibility for someone who needs a 50 Ohm terminator as it will work with 1 or 2 channels or pieces of equipment - and with no need for a cap if just one piece of equipment needs to be terminated at 50 Ohms. It is a convenient alternative to a straight/feed through terminator that also offers the utility of a T connector.
The T in the third (and fourth) photo will provide a 50 ohm termination if a cap is used or if the second side of the T is connected to another piece of test equipment (or to a second channel such as a 2nd scope channel with a 50 Ohm input). As long as a user has a cap or a second channel or a second piece of equipment to terminate then this type of T connector can be a good alternative to a straight/feed through terminator.
Net, net: I just was trying to help the OP understand the differences between the T connector and the T terminator and reminding the OP that if he gets a T connector that the T connector by itself won't provide a 50 Ohm termination (it needs a cap or something connected to the second side). In other words, it might make sense for the OP to consider a straight/feed through terminator rather than a T connector.
Having said all that, it might be good to have both a straight/feed through terminator plus a T connector with a cap (and/or a T terminator) to address various requirements.
Hope that helps clarify things. EF
- To further clarify, what I have referred to as a "proper 50 Ohm terminator" (or a "T terminator" as opposed to a "T connector") is labeled as a "Auto Term 50 [Omega symbol]" on the T terminator.