The answer depends on the signal strength and if two sets will receive enough signal strength, probably best to use a "Y" connector first and if there is not enough signal strength the best way is a 2 way distribution amplifier as near to the arial as possible (easy if it is a loft arial) and use like a "Y" connector.
How to connect a coax plug.
Unscrew it and it should be in 4 bits, Cap (metal or plastic) a crimp bit (various designs) and the bit that plugs into the arial socket.
Strip back the outer plastic of the coax cable, slide the cap of the plug up the coax, pull the braided insulation up so it bunches up, slide the crimp bit over the bunched up braiding, you should now have a white insulation sticking out of the end, strip this back so that the copper bit goes through the bit of the plug that goes into the socket. Screw it all together. It does not need soldering. The important thing is not to let the braiding touch the inner core of the coax.
As a side line my girlfriend bought a new build house with TV sockets in every room. They were all wired but only into the loft, the only one connected to the TV ariel was the living room. Why would they do this?
PS. the device pictured contains resistors to produce a voltage divider. This tends to attenuate the signal somewhat. Suck it and see I guess.
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