Pick over raspberries and discard any soft ones. Place berries in a clean 4-quart glass jar. Add the vodka, cover with a lid, and let steep for about 2 months in a cool, dark place. Stir every few weeks.
Line a large strainer with a triple layer of dampened cheesecloth and set it over a bowl. Strain the mixture through it. Bring the corners of the cheesecloth together to make a bag. Twist the ends and squeeze to extract as much liquid as possible. Discard the pulp.
Wash the jar and return the liquid to it. Let stand for about 2 hours. If there is sediment at the bottom of the jar, pour off all the clear liquid into a clean container and filter the remaining cloudy liquid through a coffee filter, changing the filter occasionally to speed up the filtering process.
Combine the sugar and the water in a saucepan and bring to a boil over medium heat. Boil, stirring, for 2 minutes, until the sugar is dissolved. Allow to cool to room temperature.
Add about 1 3/4 cups of the sugar syrup to the liqueur and taste. If necessary, add more, about a 1/4 cup at a time, until you arrive at a satisfactory sweetness. The amount of sugar syrup will depend on your taste buds and the sweetness of the raspberries. I like it less sweet, so this step is important to me.
Pour the liqueur into clean, dry bottles, and cork them.
Drink within a year before the color and flavor fade. Best stored in a cool, dark place.
(I like to wax my bottles. Get a clean tin can and put in a small pan of boiling water, then add about 1/4 block of household paraffin wax. Turn off the heat. Add a colored crayon or two, broken into pieces, and stir with a plastic spoon or a popsicle stick, until everything is melted. Place everything on several thicknesses of newspaper. Check the color of your wax on the newspaper, add more crayons if needed to get the color you want.
Immerse the top of the firmly corked bottle so that the wax covers the first 2 inches, remove it and allow to cool for a few seconds, then dip it several more times, always allowing it to cool between coatings, until you can no longer see the cork through the wax. Let wax set until firm. (Sometimes I sprinkle glitter into the outside layers of the wax, it adds an even more festive touch!). Then add a homemade label, ribbons, rafia, whatever!