Radio - input signal strength and Cu Cpi values ?

[MathWizard]

When modeling a radio in LTspice, what is a reasonable signal voltage and source impedance for a little ferrite coil antenna like in a little AM receiver ?

Also what are some typical values of Cu and Cpi for a 2n3904 or similar , I read both may be a few pF? I see at AM freq. they have huge Xc tho. I was trying to calculate them last week from the spice param's but ran into trouble, I'll try another time.