For those not familiar with this product, here's the marketing gibberish...The MFJ Ground-Coupled Portable Antenna Base gives you a stable way to mount your vertical antenna and provides an effective ground by just plopping down the base and standing on it to push the legs firmly into the ground. It'll support many multi-band verticals. You can operate 160 Meters thru 6 Meters and above almost anywhere with an effective signal. It's perfect for traveling or for semi-permanent summer/winter homes. You can easily set it up and take it down your vertical antenna for stealth operation if you live in an antenna-restricted area.
All the current that flows on your driven element must also flow on the return element or it becomes common mode current (RF in the shack). In this case, the return current flows in dirt. Dirt is a terrible conductor. It will
attenuate the return current.
A radial system provides a path for return currents that are not high in resistance. This provides a lower resistance path for return currents and you get less return current attenuation. This translates directly to more current flowing on the driven element.
There is no substitute for a conductive radial system on a vertical antenna regardless of fancy marketingspeak.
In other words... http://en.wikipedia.org/wiki/There_ain't_no_such_thing_as_a_free_lunch