Mobile antennas in general do not make good portable antennas. There are a bunch of reasons why, and this isn't the forum for that.
Some of the things to keep in mind are these: length matters. A 12 foot antenna will be at least twice as efficient as an 8 foot one.
Poor mounting (read that as an inadequate ground plane) equates to poor performance. Just a ground rod or a couple of radials might garner you a few contacts, but not nearly what a good radial field will.
Proper matching is important too, as are about 50 other factors.
If you're really planning on using a mobile antenna, visit my web site.