Question about cellular antenna

Hi,

I'm sure most of you saw cell phones with a dipole antenna like those:

../imgqa/eboard/Antenna/rf-020cark0qf4.jpg
../imgqa/eboard/Antenna/rf-f3lxowbw2cf.jpg

These antenna work best when fully opened up to full length. However, they work well even when closed down ( though having much shorter length ). How is it?

Is it a dipole antenna? what's its properties when closed or opened?



10x for every comment

If you still didn't understand my question than this is what I call an antenna opened up :../imgqa/eboard/Antenna/rf-hu5tyih5u2o.jpg

:D

I think its a helical Antenna

Yes it is a helical with dual windings to cover two bands (at least).
Sometimes this type of antenna also have a retractable part such as:
http://www.imobile.com.au/images/pho...a212i_a400.jpg
When it is extended does it make contact with the helical coil and do then work as a coil loaded monopole and retracted is the monpole isolated from the helical.

For Dual Band Helical Antenna for Mobile Appications refer to the picture attached