Budd - W3FF, published a build document for making a homebrew version of the commercial BuddiStick antenna, which is a coil-loaded vertical. As originally documented, this design is for 40M and up, and at 10M tuning is accomplished by shortening the whip. For 40M and 20M, tuning is by changing the length of the counterpoise. I'm not sure about counterpoise length for 17, 15, and 10 - see the docs. I made coils for 40 and 20, and marked the counterpoise wire for length on those bands. Budd's Google sites pages are now apparently inaccessible without logging in to Google, so I'm uploaded the build instructions here - note that I did a little rewrite for clarity and legibility. Other hams have posted design notes, including coils for 80M and 60M.
In that picture, the PVC with the "poker" on the end at the right plugs into the counterpoise winder (yellow) to elevate it. It's important to elevate the counterpoise. The green thing slips onto the top of a steel mast section, and the rest of the antenna attaches to that.
