I have previously presented my thoughts about the
similarity between dual-Z0 stubs and base-loaded
mobile antennas. Here is an article on the subject
of "Dual-Z0 Stubs" that is directly applicable
to base-loaded mobile antennas.

If we can shorten a stub by using two Z0s, why
can't we shorten an antenna by using two Z0s?

http://www.w5dxp.com/shrtstub.htm
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com