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 Tools required: Side cutters, needle nose pliers, X-acto knife, a cable stripper and a BNC crimper. The stripper is required because the different bands in the coax cable have to be cut precisely to different lengths and depths, and this is difficult to do without the proper tool. The BNC Crimper is used twice in the process - first to crimp the BNC pin to the main conductor, and then to crimp the collar over the outer insulation at the end of the operation. A quality crimper can make the difference between a connection that works and one that has to be discarded. It is also a good idea to make a length of test cable and try it out between a couple of computers on the system before actually going through the trouble of pulling cable through wall and ceiling spaces. You don't want to do all that hard work only to find you've got the wrong cabling! The connector itself consists of three parts: the connector itself, the center pin, and the crimp barrel. Prepare the end of the cable with the cable stripper tool. Leave yourself a few extra feet of cable length for mistakes. If you get a bad connector, you'll be able to cut it off and try again. Setting up the cable stripper may require some trial and error adjustment. Leave about 1/4 inch of cable sticking out the front of the stripper. You then rotate the stripper about the cable until the two layers of insulation and the shielding are cut through to their proper depths. The center conductor is about 1/2 inch long (it will be cut to fit). The exposed portion of the inner insulation band is about 1/8 inch and the braided shielding between the two insulation bands has been cut back cleanly to the same length as the outer insulation band. If the cable stripper does not completely do its job, you may have to clean up the cable end with an X-acto knife or needle file. Care counts here. The center conductor should not be nicked, nor should any of the braided shielding be exposed - the most difficult part of this operation is to strip the shielding without damaging the inner insulation band. Fit the center pin from the connector package over the center conductor as far as it will go. The resulting length of exposed center conductor is the amount of conductor that will have to be cut off for a proper fit. Take the pin back off and cut the center conductor to the correct length with side cutter pliers. It should be 3/16 inch plus or minus. Now when the pin is placed back on the conductor, its base should just reach the inner insulation band (the center conductor should no longer be exposed.) Place the pin on the center conductor, snug up the crimping tool over the pin (in the special die portion of the crimper provided for the pin) . . . and when you're absolutely sure everything is properly aligned, crimp the pin to the center conductor. Be careful. If this is messed up, you have to start over prepping the cable again with a new connector. Have a few more connectors on hand, even though you'll get good at this, mistakes are made, and if you don't have enough you'll put a real time strain on your project. You will use them! The base of the pin is seated on the top of the inner insulation band. The crimping process flattens out the pin a bit where the crimping tool applies pressure to it. Clean up any sharp edges left by the crimper with a jeweler's file, if necessary. Slide the Crimp Barrel (or collar) over the cable before installing the connector itself - we will come back to the crimp barrel in the next step, but you have to slide it onto the cable now (you can't force it over the much larger connector later). You must insert the connector unto the cable. The knurled cylinder portion fits over the pin and inner insulation band and is press-fitted-twisted into place. It has to fit snuggly between the outer and inner insulation bands, and during the process, it fights with the braided shielding for this tight space. When you think you've got the connector inserted under the insulation as far as it will go, push it a little farther. You'll know you're finished when most of the knurled surface has disappeared under the insulation and the center pin is rigid in its seated location inside the connector. If the pin is loose and the connector is on as far as it will go, the length of exposed inner insulation band when the cable was stripped is too short. If the pin is tight but a lot of the knurled portion of the connector is still showing, the length of exposed inner insulation band and/or center conductor when the cable was prepared is too long. You're almost done. Now slide the crimp barrel (placed on the cable at the beginning of the last step) up as close to the connector as you can get it. It will take some effort to get as much of it as possible over the bulge in the cable caused by the last step. If you have a general-purpose wire stripper/crimper, it has an "ignition terminals" opening that is a little bigger than the cable and a little smaller than the crimp barrel. This is a great tool for putting some leverage behind the crimp barrel when easing it over the bulge in the cable. Now you can crimp the barrel using the other, larger opening in the BNC crimp tool die. This will tighten and deform the crimp barrel down over the connector and cable for a secure connection. Crimping the barrel should force the bulge in the cable up over what remains of the exposed knurled portion of the connector to the connector's base. Now you can install another connector on the other end, and then test the completed length of cable. It is good practice to test each length of cable as you go rather than install all the connectors and cabling, and then try to track down a bad connection. With a little practice you will be installing the BNC connectors like a pro. Step 1  Use a stripping tool to strip the shielding from the coax part of the cable. You can order a good quality stripping tool by clicking here. In order for the connector to go on smoothly you will want about 3/4" of the center conductor showing and about the same amount of the copper wire braid showing (see figure 2 below). Step 2  Make sure that none of the strands of copper wire braid touches the middle conductor wire when you twist on the BNC connector. If they accidentally touch, this will not damage the camera but can result in a black (shorted out) image from the camera. Step 3  A crimp type connection allows for quick and simple installation while still maintaining a mechanical and electrical connection fairly close to a solder type termination. Some of the key points to remember are as follows: Make sure to use the proper size connector for the type of cable you are using. Make sure all cuts and stripping is clean. Avoid nicks as much as possible. Use the proper crimp tool, don't try to improvise with pliers, etc.    BNC connectors are not hard to install, but they must be installed correctly or they can cause problems down the road. Reproduced below are the instructions from Amphenol (the biggest connector maker). Here is a technique which requires no special tools other than a cable stripper and a crimping tool and which you may find easier than trying to measure the dimensions given in the Amphenol instructions below. You should have a look at the instructions from Amphenol, since some important warnings are contained in them, you may find an easier technique than what is described here.
Distinguishing between 50 and 75 Ohm BNC connectors BNC connectors are one of the few coaxial connectors that are available in two impedance values of 50 and 75 Ohms. You can distinguish the two types by the absence of dieletric material at the interface of the 75 Ohm version as shown below.  |
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