Not all ham broth is created with equal strength, so you'll need to adjust the amounts according to what you're working with. I used about 2 cups of ham "juice" (the very strong, salty liquid left after baking a whole ham) and 4 cups of ham broth that I made by cooking a ham bone and trimmings with water in a crockpot overnight. The ham broth is not quite as strong as the ham juice. Vary the amount of ham broth called for in the recipe according to the strength of what you have. If yours is pretty strong, use water for part of the broth called for to dilute it. My suggestion: start with 3-4 cups of broth and make the soup. Then taste and add either more broth or water (depending on if the ham flavor needs to be stronger or weaker) to complete your six cups of broth.
To avoid a lot of unnecessary fat, I refrigerated my ham juice/broth overnight and skimmed the fat off before making this soup.