Measuring 60 Hz AC from a piece of wire
I'm not sure if I understand your question right, but I interpret it as this:

"If I measure a 60Hz signal with a wire end or open probe connected to my Oscilloscope, does that mean anything in a noise sense?"

The short answer, not really.

The long answer includes "it might".

You can measure the presence of the 60Hz and use that to know... that the building you're in has a 60Hz outlet somewhere. It's probably powering at least your oscilloscope.

The amplitude on your scope does have a significance to the strength of the electro-magnetic field in which your wire or probe lies, but orientation, unshielded length (including the effective length any tuning components inside your probe might add) will have a large influence in how much it picks up.

As does the design of whatever you are measuring the noise for. In your case the antennas, the length and orientation, as well as any tuning components such as inductances and capacitances to make them resonate - or get them to (partial) wavelength -, will have a great effect on the voltage at the amplifier. An antenna can go through some simple steps to swoop up to 10's of volts, or can drive only microvolts, depending on the level of tuning to the intended signal.

((60Hz is a very long wave though, so tuning will take "large" components))

So, in a shorter form: If you know the exact specifics of the thing you are measuring as compared to the eventual system, yes you could potentially get an impression, but just hooking up a scope to a wire and saying "Oh, look, an antenna like this will give a 20mV signal on my eventual set-up" is (almost) never going to work that easily. Things like grounded bulk alone might make differences (your scope has a big metal case connected to power ground and this might have an effect).