We are using a internet provider modem ( Sagemcom F@ST 1704) that is located on the ground floor of a old farm house. The signal strength can range for good to poor downstairs when using a laptop. Upstairs my son's PC signal the signal is usually poor or goes out all together. W have looked at home plugs, extenders and such but are confused as to what might work in our situation. Another way to go would to buy a different modem, but we would rather not spend a lot of money. Any suggestions would be appreciated.
You have a few different options. Really comes down to what is more convenient and cost effective for you.
1. Move and re-position the modem/router if able. Most wireless access points use omnidirectional antennas. So the signal gets pushed out in all directions. A more center point in your home would be ideal. Even re-positioning the access point may yield favorable results if its being blocked by large objects.
2. Keep the modem, but purchase a router with a wireless N rating. This would benefit you if the wireless devices up stairs use wireless N adapters. You would basically hook the modem into the router's WAN port and then all devices would first connect to the router to gain internet access from the modem.
Just one. Ethernet from the modem to the wireless router. Now before diving into that option make sure its something that's beneficial. See what the current modem/router your isp gave you is rated at. Either G or N most likely. Then check to see what your sons laptop is rated at. Again its probably going to be either G or N. These ratings are wireless ratings. N being the faster/newer rating.