A log periodic is similar to a discone in that the shining attribute is
wideband coverage, not gain. If you look at the gain curves, and F/B, you will
see why the manufacturers often quote maximum gain, not average gain, and I've
never seen a gain or F/B ratio plot as a function of frequency in their ads.
As long as you know what you're getting, you won't be disappointed.

73s,

Evan