I would also like to mention that you can make an inexpensive, yet very effective sharpening "system" from a couple of sheets of , progressively finer, wet-r-dry sand paper, the type used for body/metal work.

Find a couple of nice boards, glue the paper onto the boards, wet down the working area of the paper and have at it.

For years, when I was on the "trade show" circuit, I would just pack a "multi-pack" of this stuff in with my knives and luggage to keen up the edges of my knives.
I started with 440 and worked up to 660 or 880. Just a few strokes on each side does the job. When I traveled I would just put the paper on a really flat table and go from there.
It is economical and really does a great job.