A couple of videos from Waters and Stanton looking at the Diamond BB7V Vertical Antenna for 2-30Mhz. Ideal for those of us with smaller gardens or for use when out away from home.
HF Vertical Antenna Type: Broadband - low SWR
Power Rating: 250 Watts.
Mount Type: Non-tilt bracket
Connection Type: UHF female - SO-239
Price is £289.95
Link: CLICK HERE
You could of course get similar results with a fishing pole, balun, and a length of wire so I guess you are paying for the convenience and ease of use that this antenna provides and although the specs say you don't need any radials I would suggest using some if possible to get the best out of the antenna.