This September marks 41 years of amateur radio for me. As far back as I can remember radio operators have been telling other operators that the more radials you have the better off you are. The only time this is a accurate statement is when they are either buried in the ground or laying on the ground. The minute you elevate the feed point of the vertical antenna to a height above ground of at least 0.08 wavelengths and the radials to a minimum sloping height of 2ft. this statement no longer applies. As a demonstration of what I am talking about I have modeled the now classic Buddipole as a vertical on 20m. The first model has four elevated radials each one is 1/4 wavelength long. The VersaTee/ Antenna feed point is located 10 feet above ground. Each radial slopes back down to a point 2 feet above ground. All of the models have the same set up except for the amount of radials.
Note that this is a positive gain figure, compared to a classic ground mounted vertical with buried radials that typically has a negative gain figure.
As you can see compared to the four radial model above the gain is about double.
As you can see compared to the two radial model above, this model using a single elevated radial has the highest gain. About 1/2db higher than the two radial model above. The reason why this happens is when you have two or more radials, the radiation coming off of each one cancels the radiation coming off the other ones. This leaves only the vertical element to produce radiation. So the next time someone ask you how many radials do I need you should say it all depends.