We bought new house and I need to test network (RJ45) and coax jacks to see which ones are working. How can I do that without actually connecting computers/cable boxes?
Very good question but you need to find out more information.
The very first question on my mind is.. Where do they connect to ? if they are connected to anything else at all?
Find the starting point(A) and the end point(B) of either cable.
Using a multimeter and a return cable you test continuity of the cable. Either using Ohms = 0 which means short circuit(in this case good because the cable is good) or some meters have buzzer if there is continuity.
RJ45 Netw4rok cable used for 10/100Base Networks.
This is very time consuming because RJ45 have several strands of cable so testing one after the other can be beach. But one clever solution is to make a loopback on point B and test the correspoding points on PointA. If any one does not loop back then the cable is most likely broken.
There are also network testing equipment that do the same as mentioned above.. but you have nice flashy lights and a nice loopback box supplied.Ebay a few bucks each for el cheapo ones.
Coax is a funny one and depending on what you need it for. Coax for TV, satellite or CCTV again. just test using a multi meter test the two end points. Center to Center and Shield to Shield. An extra step here is to test for short circuit between singal(centre) and shield) so just on one end using ohm, test center and shield and you should have NO reading(not 0ohm0just nothing) If you get a reading at all you will get interference and the cable is likely to be damaged or unusable.
The other part if its used for a network then it all has to be connected and terminated to test it(but its unlikely its used for network because these types or network have been eradicated because of unreliability)
This will only test if the cables are in an operable state. So you connect it and it will work. The bandwidth, noise-to-signal and interference will greatly depend on the quality of the cable, workmanship during installations, etc.
EG The RJ45 could be rated for Gigabit but your bandwidth could a mere 250mbs(1/4 bandwidth) because the shielding has not been done properly, or the ends have been poorly installed, the cable is near high voltage lines, the cable is severely bent ins several places along the way.
COAX in general either works or not.But for Analog Video; again many factors come into play. For digital(eg satellites) it should be ok