Using one antenna for all frequencies will cause you trouble no matter what the ad's in the ham magazines say. Make your own cut to frequency and you won't have to deal with this stuff.
Have you tried a low horizontal sky loop? Those are normally good for 80 through 40. Make it as long as you was but don't hang them more than 20 ft. off the ground. Wayne Green said to feed them with 50 ohm coax, but he also claimed to have worked dx on a 120 watt lightbulb mounted 8 foot tall 4"x4" wooden fence post.