This install guide depicts a RP-SMA male connector onto LMR-400 coaxial cable. The techniques used in this installation guide can be used for almost any crimp on type connector.
We will start with the “FAQ” in order to save you some time at the beginning.
Connector Install FAQ
1.) The center pin is not going onto the center conductor of my coax.
It could be one of two things. If you have a solid center conductor on your coax, be sure that the center conductor is round. When you cut the coax to length, a diagonal cutter cuts by applying tremendous force to a small surface area which can “flatten” the center conductor. Use your pliers to squish the center conductor back into a round shape and it should work. If you are using a coax with a stranded center conductor, when cutting the coax, this may have “squished” the strands of the center conductor which may have loosened the wrap of the center strands. You may need to squeeze the strands back together, with your pliers, while twisting the strands back to as tight of a wrap as possible to make the center conductor smaller in diameter. If this does not work, you can use your small diagonal cutters to cut off 3-4 strands of the exposed center conductor which immediately decrease the diameter of the wrap. Some people will cry foul of doing this, but once you solder it, who cares… Its all in one bundle, so… meh =) Ill be making helium and they wont.
2.) I melted the dielectric of my coax.
You definitely want to avoid this where possible. By applying the soldering iron under the point to be soldered, the heat will rise quickly heating the work area. You will want to have the solder on the work at the point at which to be soldered. Once the solder starts flowing, let just enough in to give a coating onto the center conductor and so that the solder pools and fulls the “hole” in the side of the center conductor. This will provide the best connection, stop the center pin from coming off, and making the center conductor only needing direct heat for a very short duration.
Installing the RP-SMA Male Crimp-On Connector
We will begin by installing the RP-SMA male crimp-on connector on a piece of coax. This process is the same for all the types of coaxial cable that fit this RP-SMA male crimp-on connector. These connectors fit on a wide range of coax types, including: RG-11, RG-213, RG-213/U, RG-393, RG-393/U, RG-8, RG-8/U, RG-8A, RG-83, LMR-400, LMR-400 Ultraflex, Belden 7810A, Belden 8216, Belden 83269, Belden 83284, Belden 84316, and other 0.39 and 0.405 Inch OD Coax.
Identify all connector parts (3 Parts):
Each connector consists of one body assembly (plug), one rear ferrule (crimp sleeve), and one center pin (plug contact).
First cut your cable to the desired length and then strip the black jacket back approximately 0.54 inches. When the jacket is stripped cut the braid/foil back 0.23 inches from the fresh cut end. Finally, cut back the dielectric 0.12 inches from the fresh end down to the center conductor. The braid needs to be cut back further than the dielectric to insure that none of the braid or foil is touching the center conductor which could cause a short.
Note: Do not nick the braid, dielectric, and center conductor if at all possible. Tinning of the center conductor is not necessary if contact is to be crimped. For solder method, tin the center conductor if the center is stranded. twist the center conductor very tightly prior to tinning.
Install Method Selection:
Slide the outer ferrule onto the coax as shown below. Flare the braid slightly to allow insertion of the connector main body. Important: Do not comb out braid.
Place the center contact on the center conductor of the coax so that it butts against the cable dielectric. The center conductor should be visible through the solder / inspection hole of the contact. Crimp or solder contact in place as follows:
Use the 7505-DIE-400 with a hex of 0.128 and 0.10 installed into a 7505-HANDLE Ratcheting crimp handle for the center pin. Start by using the large hex of 0.128 on the pin crimp location. depending on the coax being used, you may need to use the 0.10 hex in order make a secure connection. (DO NOT OVER CRIMP / CRUSH THE CENTER CONDUCTOR)
Make sure the solder hole is facing up. Touch the soldering iron to the underside of the center pin directly under the solder hole. Touch the solder to the center conductor through the solder hole on the center pin. Allow the heat from the metal to melt the solder so that it wicks into the center pin. Once the solder melts it only takes a tiny amount of solder to make the connection. Do not allow the solder to pool over the solder hole. The outside of the center pin should be free of obstructions for insertion. Do not over heat the center pin which could cause swelling of the dielectric of the coax.
Main Body Install:
Install the cable assembly with the center pin already affixed, into the main body of the connector. The Install the cable assembly with the center pin already affixed, into the main body of the connector. The knurled portion of the main body slides under the braid of the coax. Push the cable assembly into the main body until the center pin snaps into place in the dielectric of the connector.
Slide the ferrule (placed on the coax at the beginning of Step 2) over the braid and completely up against the connector body. Using the 0.429 hex of the 7505-DIE-400 installed into the 7505-HANDLE ratcheting crimp handle, crimp the ferrule at the location shown in the picture below (on the ferrule, but right up against the main body of the connector).
When this is completed, as a final test, you should always check resistance from the center pin to the body with an ohmmeter in a low resistance scale. After verifying that there are no braid – to – center pin shorts on the other end of the coaxial cable, you should see infinite resistance (open). This completes your RP-SMA male crimp-on connector installation, and the connector is ready for use!
Weather seal your connections
A good additional step is to use your coax seal to seal up the connection points where you only used crimping. See picture below:
Download a PDF copy for your use
You can download a PDF copy for your later use here: