Here's a simple formula to save you money since I've heard that same
roll of wire is now around $45! No matter how long your radials are,
put the ends down such that they are ~0.025 wavelengths apart on the
highest frequency band you plan to use. On 160 this is ~13', on 80
6.5' and on 40 3.25'. This works out to about 63 radials total if they
are all 1/4 wavelengths long in a circular configuration, but the
formula also works for random lengths in non-circular configurations.
The idea is to have the end points no more than ~0.025 wavelengths
apart. While ON4UN's book suggests 0.015 wavelengths apart, some
recent measurements by N6LF seem to indicate that may be overkill (i.e.
60 radials are within a few tenths of a dB of 120 radials).

http://www.antennasbyn6lf.com/files/...asurements.pdf

73, Bill W4ZV
At $45/500 feet it is still a long way from Cost prohibitive.

Do I misunderstand? My intuition is to place the radials I use over as
much area as I can. The way I read your note is that they should be
installed in a small sector... I think I am misunderstanding that
point.

Also, on the distant planning horizon I will likely use the Radial
field for a permanent Multi band Vertical. The current 28 foot
radiator is simply a convenient place to gain experience.

I am inclined to pursue the advice presented in the article
http://www.ncjweb.com/k3lcmaxgainradials.pdf
John Ferrell W8CCW