How does the near field off end of rubber duck decline?

[deh6]

Most radio controlled model airplane folk "believe" that a rubber duck antenna on their transmitter radiates best off the end, so a common saying is passed around: "pointing a whip at the model is bad; pointing a rubber duck is good." Clearly, the far field off the end of rubber duck antenna is a null. The literature is quite clear. For the far field it behaves as a short monopole. However, the people become "believers" because they test out their trasmitter (72 Mhz) at relatively short distance, e.g. 50 feet (roughly 4 lambda) and find that the rubber duck works best pointed at the plane/field-strength meter, etc. and the whip does not. For example--

http://www.bergent.net/antenna_field_test.html

How do the near field effects drop off with the small helix, compared to the whip? (Or, what would be a simple demonstration that pointing a rubber duck at the model produces the weakest signal.)

 

[Higgler]

For small antennas, the material around them shapes the antenna pattern. For larger antennas, it's the antenna itself that shapes the pattern.

I'd expect that reflections off the ground or human reradiates more from the duck and fills in the null off its' end.

You won't see near field effect more than a wavelength or two away. I've seen monopoles and dipoles used for heating human tissue and the tips of these do an equivalent amount of heating as the high current points.

kch