Here's some more information on screwdriver HF antennas:

http://www.qsl.net/k4kwh/
http://www.hsantennas.com/
http://www.kj7u.com/
http://www.ko6yd.com/sam/index.htm
(screwdriver antenna memory tuner)
http://www.mfjenterprises.com/produc...rodid=MFJ-1662
http://texasbugcatcher.com/
(my antenna uses Henry's coils but is not a screwdriver.)
http://www.mindspring.com/~k4poz/

As you can see, these antennas are very respected by the finicky ham radio
mobile operators. They'll ALL tune ALL the marine bands.

Larry W4CSC