Articles for Amateur Radio Newsletters aimed at new hams
 written by Gerry Crenshaw, WD4BIS, Rowlett, Texas

 

 

NHP #5: What kind of Coax Connectors do YOU use?

All of the Amateur radio equipment we use will have some kind of coaxial connector associated with it. What kind of connector to use will depend on a lot of things. Generally you are better off to stay with the connector that came with the antenna and buy a connector adapter to get to the connector on your radio.

Common Coaxial Connector Types

Coax connectors come in a wide variety of sizes and styles. There are several common types familiar to most of us. They include the PL-259, BNC, TNC, N, RCA, and F connectors. Manufactures do not really have a standard when it comes to picking a connector. They tend to use connector that space on the radio permits. For this reason you will find the smaller connectors such as the BNC, threaded RCA or F connector used on handi-talkies, and the larger connectors such as the PL-259 or N connector used on mobile or base equipment.

Typical Antenna Connectors Today

Most 2 meter antennas come with a PL-259 coax connector, most of the 440 Mhz (70 Cm) antennas come with an "N" connector. Partly this is done because of the abundance of dual band equipment found today. This was an easy way to keep the two radio/antenna systems from being mis-connected. Again this is a typical however it changes radio type to radio type and even from year model to year model.

Making Coaxial Cables for the shack

Coaxial connectors usually have very specific dimensions for cutting the shield, dielectric, and center conductor. This is so that inside-the-connector items such as the shield will snug up. These dimensions need to be followed and not "eyeballed" to make a reliable connection time after time. Practice making jumpers with a connector you have not used prior to cutting off the connector that came with your antenna. Coaxial connectors are easy to make mistakes on. Melting the inside dielectric and shorting the center conductor to the shield is a very common problem. Practice is your best defense against this.

N Type connectors have lots of small parts and there are several different sizes of N connectors to mate with the different coax types. There are Specific N connectors for RG-8, RG-213, RG-214, and 9913 type coax. When buying N connectors be sure to know what type of coax you are terminating.

Connectors such as the PL-259 have one base size for the RG-8 coax and then an adapter is needed for the smaller coax such as the RG-58. Again, know the type of coax you are terminating prior to purchasing the connector.

The standard R.A.C.E.S. antenna connector for the Dallas area is a PL-259. Have an extra adapter to convert your connector to this connector if you plan to join an emergency service group.

Surplus Connectors

BNC connectors are made to terminate just about every type of coax made. This includes 50, 75 and 93 ohm coax types. They are readily found on the surplus market and it’s easy to pick up the wrong connector, thinking it’s for your coax. Because of this it's easy to make a cable for the shack that works for a short time and then degrades in performance very quickly. I have found that BNC connectors from the same manufacturer won't mate correctly with connectors from the same family. Amp Inc. and Amphenol both admit to this problem and state that due to center conductor size differences, and dielectric size differences between different impedance coax, the connectors are made to accommodate this. When purchasing these connectors surplus, caution should be the watch word.

Following the manufactures guidelines on connectors will make for good signal report and maximum transmitted power. Make your cables with care and check them prior to use. All of these things will keep your signal strong and clear

73’s and GL

Gerry WD4BIS

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Copyright 2005 Gerald Crenshaw WD4BIS. All rights are reserved.

Permission in advance is granted to those who use this for non-profit Amateur Radio club newsletters as long as it is used unmodified including this copyright notice and that notice is given to the author via email (wd4bis@arrl.net). In addition, please forward a copy of any newsletter this appears in to: Gerry Crenshaw WD4BIS, c/o GARC, 1027B W. Austin St, Garland, TX, 75040

Web site maintained by Janet Gobeille Crenshaw (WB9ZPH)