Hi Matthew
Dave has has got it spot on with regards horizontal mounted antenna. These are really only ok for skip and not so good for local chatter. After a quick Google search I'd be inclined to try the double bazooka as this is basically a wire dipole. It will be directional (signal is radiated 90 degrees to the antenna).
Personally I'd be trying possible to get a vertical up. Even if its a t2lt on a fibreglass pole that can be put up and down as required

Hope this helps
James. 26JS07 (26AM07)