Ethernet over RG59 cable

Hi,

I need to connect my first and second floor. Recabling would really be a pain. Wifi doesn't work properly. Ethernet over power lines doesn't work either (too old electrical system) but ... I have a cable TV RG59 coax cable (75 ohm - length about 50 feet) which goes from near my router (2nd floor) to a place where I could set up a WIFI access point (first floor).

I thought that I could use a 93 ohm to 150 ohm balun to link my router to and hope for the best using the following scheme.

Router <-> RJ45 cable <-> Balun <-> BNC ended RG59 75 ohm cable <->Balun <-> RJ45 cable <-> Wifi Access point

Is it worth trying? Any chance it could work, even if it doesn't give me the full speed of 100 mbps ethernet? Has anyone tried that type of setup?
Any other idea?

Thanks in advance

Pierre