Answer of sorts (or, not an answer at all) to questions about rubber ducky antenna. This follows the comments dialog above as this post is too large for a mere comment.
I volunteered to run the NEC2 calculation for this antenna and after the OP provided more details I started doing back of the envelop computations since I am away from my main computer for a few days (where I have NEC2/NEC4 and my Mathematica solution modules). I did a simple reactance calculation of the coil itself at the designated frequency of 462 MHz which is open for FRS/GMRS operations that I think is associated with the rubber ducky antenna of the HT.
The inductance is approximately $0.43\,\mu H$ and the resulting inductive reactance $X_L$ is:
$$
X_L = 2\,\pi \, f\, L = 2\times 3.14\times 462\times0.43 = 1248\, ohms\qquad \text{(rounded)}
$$
This rather large impedance means that this rubber-ducky (for it to work at all) has high capacitive coupling to the HT and even probably to the person holding it which naturally form part of the antenna system.
Therefore, I posted some questions on NEC2 distribution list and one answer (from the creator of EZNEC, who is a Guru/Wizard with NEC2 and NEC4) provided these comments (quoted directly from his e-mail):
It's not practical to model with NEC-2 for several reasons:
The "ducky" is only a part of the antenna system. At least as important, and likely more important, is the person holding the radio which can have a major impact on the pattern. Whatever the current flowing into the base of the "ducky", an equal amount of current flows along the outside of the radio and the person holding it. This current causes radiation just as the current on the "ducky" does, but from a much larger "antenna".
My experience is that modeling an inductively loaded antenna as a wire with one or more ideal inductive loads doesn't provide accurate results. I believe this is because the current changes significantly from one end of the actual loading inductor to the other, while currents are the same at the ends of idealized loads. Even using multiple loads doesn't do as well as modeling the actual inductor as a helix.
NEC-2 requires that wires be spaced at least several diameters apart. A typical "ducky" helix has turns spacing closer than this, making modeling the inductor portion of the antenna as a helix questionable.
NEC-2 doesn't take into account proximity effect, which might be significant with closely spaced helix turns. Presuming you're trying to evaluate the efficiency of the "ducky", this means that the efficiency shown by the model will be overly optimistic even if you use realistic values for wire resistivity.
NEC-2 has no way to account for the dielectric surrounding a "ducky". This will alter the resonance of the antenna in a way not predicted by the program.
Sorry, there are just some things that can't be practically modeled with NEC-2. This is one of them.
End of Quote.
So, sorry to say that when I get back home I will probably not try to model this antenna as I volunteered to do. Hopefully though, there is sufficient content in this answer to give the OP more information to make judgements or decisions regarding the rubber-ducky antenna.
