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20180616 - Terminating a BNC connector

posted Jun 15, 2018, 6:55 PM by Onno Benschop   [ updated Jun 15, 2018, 7:01 PM ]
Charles NK8O has written this description on how to terminate a BNC connector.

First, I use 90 degree angled BNC connectors because there is no center pin with which to deal. It removes a level of complexity from the process.

Since I am making mostly jumpers for the shack, I use RG8X cable. It is flexible enough to be manageable and small enough not to be cumbersome.

BNC 90 degree crimp connector for RG8X/LMR 240. Don’t skimp. Use good quality connectors like Amphenol. That’s what I use.
Inside the connector is a notch for the center conductor.
ALWAYS remember to put your heatshrink (if desired) and the ferrule on the cable FIRST. (Don’t ask how I know this!)
Measure out the length so you have an idea where to strip. You can mark this or eyeball it, if you clever.
Use decent quality tools to do your stripping and crimping. Those crimpers are available at hamfests or rallies, and also from Amazon or your local Amateur Radio candy store.
Do the “deep” cut from the tip first. Note there is an indication on the tool to show the direction to turn. Do NOT make an excessive number of turns or you will damage the center conductor. This tool was purchased with a cable TV crimping set for RG6 - same size as RG8X.
This length is good. If you are very fussy, you can allow the white inner insulation to go all the way to the solder point, but it’s not necessary.
Then strip the outer sheath. A good tool requires ONE turn. Otherwise you cut and fragment the shield weave.
Flare the braid and insert the wire in the connector. The inner conductor should just rest in the channel.
Bring the ferule up into place. It should fit semi-snugly on the braid. Push everything up into the connector until there is no inward play, and make sure the ferrule is snug against the body of the connector.
Engage the crimping tool with everything in place, and crimp. The top of the tool (with lettering, etc., goes toward the body of the connector.
A good crimp will have a uniform hexagonal shape. The bottom flares, uncrimped. Some folks like to try to crimp all the way down with a second pass. I think it usually makes them look sloppy.
Use a HOT soldering iron or it will take you all day to heat the wire and the channel brass. Tinning is not necessary if you heat everything properly, except to tin tip of the iron to facilitate heat transfer. Temp shown is Farenheit, which about 480C. The hot iron allows you to work quickly.
Hold the work in place with a “helping hands” to avoid burning yourself. I like to wrap something around the ferrule to prevent scratches, even though it will be covered with heatshrink.
Solder should show a good “flow". The trick is not to allow any to go down the outside of the channel support or drip inside the connector. This is a good time to check for shorts with a multimeter.
This is Harbor Freight heat gun. Harbor Freight is a tool and utility chain in the US. A heavy duty hair dryer *might* do the job, but many do not get hot enough. Excuse my green scrubs - it’s my work uniform!
Heatshrink is cured in place with the heatgun, and the cap is installed over the connection. Tighten the cap gently and the process is complete.
The final product with a PL-259 at the other end. The method of crimping is identical, although the measurements are a bit different. With the PL-259, be careful to keep solder off the outside of the center pin. This is a 1 metre long cable.

#tutorial #nk8o #soldering #crimping #bnc