Retired Techie

Getting older, not necessarily wiser!

Compression Fittings on Coax Cable

Published on May 19, 2022 at 7:13 pm by LEW

Introduction

Have you ever had problems properly securing compression fittings on coax cable? Apparently lots of people do.

On a recent side job, I was helping one of our neighbors install a CCTV system, and were using siamese cable. They were also using BNC compression fittings. Both were materials I have not worked with much in the past. Back in the day, when I used to do a lot of work with coax and connectors, it was always solder on connectors. I used to have a small butane powered soldering iron to use when installing connectors on ships yard arm, or halfway up a tower.

One thing I noticed, some of the people working on the project where having a difficult time getting the BNC compression connector to properly secure to the end of the RG-6 coax cable.

Since then I have watched a lot of videos, and read several tutorials on this process, and done a bit of testing on my own. While generally decent, my short experience (with limited cable and connector types) tells me that in many cases there are a few specifics that need to be focused on a little more in order to do a working compression fitting on coax.

The Equipment I worked With

As mentioned above, the coax part of the siamese cable was RG-6. I am not sure of the brand of the compression BNC connector, though I don’t think it was overly expensive.

 

The compression tool had a name and model number. I looked it up, made in China and ₱ 650 in the Philippines (about $12 US). While this worked, if you are going to be doing a lot of compression fittings, I would suggest investing in a higher quality tool.

With the tool I was using, I found technique seemed to be more important than the quality of the tool. After a few test compression’s, I was able to achieve 100% functional connectors. We will see how they hold up over time.

The Technique

1. Ensure you have the right size compression fitting for the coax cabled. Generally not a good idea to try and put a RG-59 connector on a RG-6 cable, or vice versa.
2. Examine the end of the coax cable, it should be a round clean cut. Not squished, which can be severe sometimes when using inferior or dull diagonal cutters. You can sometimes use needle nose pliers to round it out again.
3. Remove the insulation, I recommend using a good quality coax cable stripper. Otherwise I would suggest using a box cutter, rather than a cheap one. I get better results that way. You will want to strip back the outer insulation about ½”. If using a box cutter or cheap tool, be careful not to cut the metal braid just under the outer installation.
4. Cutback metal braid and remove a ¼” of the inside installation. The advantage of using a good quality tool is that steps 2 and 3 can be done at the same time. Note there should be a metal foil shield around the inside insulator, but that may vary depending on the quality of your coax.
5. Fold back the metal braid. You should fold back the metal braid over the outer insulation.
6. Double check your measurements. You should have a ¼” inner conductor exposed, ¼” metal foil and inner insulator, and a ¼” of braid bent back over outer insulator. Make sure the inner conductor is straight.
7. Push the prepared end of the coax into the BNC compression fitting. Make sure the center conductor is centered as you insert the cable into the connector. A short way in you will encounter some resistance. This is where most of the issues I saw occurred. The installer assumed that at first resistance the cable was all the way in. It is not! You need to keep pushing and possibly do a small +/- 5 degree twist. The connector should slide on further. The metal braid should not be visible once the cable is all the way in.
8. Once the connector is fully seated on the end of the cable you can use the compression tool. Make sure the correct adapter is installed for BNC type connectors, and follow the instructions that came with the tool.
9. Once the connector is fully compressed, do a strength and a short test. During the strength test remember this is a compression fitting. I have seen installer break solder on connectors by over doing a strength test.

Conclusion

There yo have it. Using the above procedure I was able to successfully install inexpensive connectors, using an inexpensive tool with 100% success rate.

If I end up doing this on a regular basis (another neighbor is already asking for help with their CCTV and cable TV), I am going to have to get my own set of quality tools.

Copyright © 2021-2024 Retired Techie All rights reserved.