Coax number flaw


Compliments of Firestik® Antenna Company Technical Support Team

Copyright © 1996 Firestik® Antenna Company

If you have ever installed an antenna and needed coaxial cable, there is a good chance that you paid a premium price for less than standard grade cable. Unless you have knowledge regarding issues related to coaxial cables or have a very trusting relationship with the organization where you are planning to purchase the cable, it is wise to proceed with extreme caution. Over the last 20 years vicious competition in the coaxial cable industry, especially in the pre-made assembly sector, has allowed the market place to be flooded with low-grade coax and you may never know it.

The current cable designation numbers are at best severely flawed. How are coaxial cables identified? Well technically, only cables that are made to U.S. Government specifications can be marked with the "RG" designation. But in reality, many manufacturers/importers pay little or no attention to the requirements. In those situations, it is up to the purchaser to demand that specific standards be fulfilled. However, as sadly as it is, most of the energy goes into bickering over the cost instead of the quality. And even if the cable carries the designated number, there are often cost cutting activities going on right under your nose. Following find the designated characters legend for cables.

R - Means: Radio Frequency

G - Means: Government

8 - The number in a government assigned approval number

/U - Means it is a universal application.

Letters that appear before the /U characters (i.e. A, B or C) means a specification modification or revision. For instance, it is common in the CB industry to see the designation RG-58A/U. The original RG-58/U coaxial cable had a solid enter conduct. The "A" modification replaced the solid center conductor with a more flexible stranded center conductor (that is highly recommended for use in mobile installations).

So, where is the flaw in the numbering system? The numbering system flaw is that there are no hard character designators that indicate the type or quality of the extremely important shield. Typically, the minimum shielding coverage on "RG" cables used for CB and amateur radio is 78%. That is, 78% of the insulator that encapsulates the center conductor is covered (or shielded) with the over-laid copper braid. Firestik, by choice sets the shielding specification on all their cables to 95%. In contrast, we have inspected cables that end users were using on troubled set-ups that had coverage as low as 52% and their problems were solved by simply upgrading the quality of the coaxial cable.

Shielding is very important when it comes to keeping unwanted RF interference from entering the cable. Furthermore, when it comes to delivering energy to the antenna, even under standard 4 watt CB outputs, holes in the shielding creates openings for energy losses. There is barely a day that goes by that our technical staff doesn't fix a user radio performance problem by doing nothing more than having them upgrade their coax. In our business, whenever someone is experiencing poor performance they go right to the antenna. Little or no attention is given to the coaxial cable or the antenna stud mount whose responsibility is to deliver energy to or from the antenna. Our standard story is, "If you bought a twenty-five dollar nozzle and connected it to a garden hose that was full of pin holes, would you blame the nozzle or the hose?" Unfortunately, you can't see RF leaking out of the coaxial cable … but it certainly does from low shielded cables.

Pay attention to your coaxial cable! If you want your antenna to perform to its potential, make sure that your feedline and antenna stud is capable of delivering the goods. And once installed, avoid sharp bends, pinching conditions, exposure to extreme heat (which could melt the outer covering) as well as situations where rubbing against a sharp surface could wear a hole in the covering. And under no circumstances should you ever splice the coaxial cable together as you might a common wire. Do not settle for anything other than the best.

Firestik Antenna Company -(Tel) 602-273-7151 -

Updated: 2023.12.05

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