The W3EDP end fed wire antenna lends itself readily to QRP and portable operation.
A simple matching unit is needed to couple the wire to the rig and a counterpoise is required for some bands, however there is room for experimentation here.
It has been shown that different lengths or removal of the counterpoise altogether, can improve performance, as described in RadCom, August 1996 by G3LCK.
The Tuning capacitor in the AMU can be a 365 - 500pF broadcast type or a miniature version is OK for QRP use.
Counterpoise lengths
Tuning Unit
Values for coils in the unit, based on a 2 inch former and 16 swg wire:
Frank G3YCC
K3HRN Notes:
Some folks have told me the modifications below make the antenna something other than a W3EDP. I can tell you that it works very well with 5 watts.
Create a "bundle" of counterpoise wires, 1/4 wave length for each band you will use. Attach the bundle to the tuner in place of the counterpoise pictured above.
Be cautious, 1/4 wave length elements can have high RF voltages present, even at QRP power levels.
I've been able to work 160-10, including WARC bands with this type of antenna.