This is a half-recipe handed down to me by a dear friend. The jam is not too sweet, with enough ginger to be noticeable, but not too heavy.
Put all of the ingredients into the large pot. Either layer them or mix. Let the mixture stand at room temperature for at least 1 hour, until all the sugar dissolves.
On low heat, bring the mixture to a simmer. Continue cooking until the jam is thick but not sticky, stirring frequently. Cooking time varies considerably. The range Deborah provided for a double recipe (using 4 pounds of pears) was 90 minutes to almost 2 hours. I found that my 2 pound batches took about 1 & 1/2 to 1 & 3/4 hours, i.e. 90 - 105 minutes. To test for doneness, either use a thermometer (done at 220 degrees F/105 C or use frozen plates. The plate test requires freezing the plates until quite cold (I put them in the freezer when I start the jam cooking.) Remove a plate from the freezer. Spoon a small amount of jam onto the plate. After a minute or so, when it is cool enough to touch, run your finger through the jam. If it has a skin and does not run, it's set. If it is still runny, let it continue to simmer for another few minutes and test again.
Once the jam is ready, remove the pot from the heat. Let it sit for about 5 minutes, then ladle it into the jars, clean off any drips with a moistened cloth and close the jars. Refrigerate
For a good description of the plate test and another way to check for doneness using the spoon (the "sheet test"), see Food in Jars, a wonderful resource on canning.