One way to approch the problem.

The bevel could be sharpend with Hand Stones or Diamond Files (the hand ones not powered ones).
Remove the Blade and savely mount it with the cutting edge facing up. Lay the Stone or Diamond File (They also have Diamond Stones) on the bevel of the Blade and draw the stone the length of the Blade keeping the same angle that the bevel is at.
The still here is to keep the Stone exactly at the bevel Angle and if it is extremly dull to be willing to send an hour or more shapening a 17 inch blade.

You also need to wear Gloves and work slowly because you can easily cut yourself.

Do an ebay search for Diamond Sharpening Stone and/or Diamond Files.

The bulk of the Diamond Files on eBay are small ones about the size of Jewlers Files. However, I have 2 that are the size of normal Files. I got them at Harbor Freight but I don't think they sell them any more.

Well I have been looking on eBay and I have not seen any large Diamond Files. However, there is a Honkong Company selling a single 2 sided Diamond Sharpeing Stones for about $10.

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