Klaus is absolutely right. Nobody told you to make an antenna out of co-axial cable.
That kind of cable is used as a conduit - a way of carrying a signal some distance away while retaining its integrity and shielding against signal leakage or ingress. Its the pipe that carries the signal, not the antenna.
There is nothing stopping you adding an antenna at the end of the co-axial cable, that is what most of us do.
What we have stated is that if you do not use co-axial cable correctly you will leak signal from it and in doing so it will behave like a leaky pipe, its contents will escape. That is why you could see some of that escaped signal on your analyzer.
If you do not connect the co-axial shield (the braid around the center wire), or you connect the shield to the output of your signal source, it behaves exactly like an ordinary length of wire so there is no advantage over not using a plain wire instead.
Brian.