BNC is a UHF constant impedence connector. They work
very well at
several GHz! They just don't like high RF power (voltage).
They are not that great, compared to later connectors. The F (a quality
one) will do a better job in the UHF region.
When BNC started to be used for Eithernet, Ts were
expensive and got cheap
due to volume. F connectors are common to cable industry and if they
needed Ts they would be cheap too.
Actually, BNC Ts were quite common back then. They were used in radar test
sets quite a bit. OK, being military, they were still expensive...
William Donzelli
william(a)ans.net