Radio World: Home-made adapter can get you out of trouble

Radio World: Home-made adapter can get you out of trouble

Radio World: Home-made adapter can get you out of trouble

The medium wave transmitter feeders are very forgiving. If you do not have the correct coaxial connector, it will usually suffice to have tape or copper tubes, especially in case of emergency and lower power. When it comes to VHF / FM it is not so simple, and if you must run a transmitter for a lapse with a dummy load and the 1 kW transmitter has a female N-type connector and the dummy charge ends on a 339 IEC 50-80 bullet (3-1 / 8 inch EIA), what can you do?

Figure 1: Adapter for a homemade connector that attaches to a 3-1 / 8-inch EIA connector. Figure 2: For low power tests, this adapter is coupled to a dummy load. Figure 2: For low power tests, this adapter is coupled to a dummy load.

You can buy the appropriate adapter, but the price is high. Another solution is to do something less expensive that works equally well.

The first step is to cut a piece of RG214 coaxial about one and a half meters in length with a male N-type connector at one end. The length is not crucial but gives you enough cable to route from the transmitter to the dummy load.

The other end is prepared by peeling about 6.5 centimeters from the outer insulation. Then the braid must be cut so that about 5 centimeters of the central conductor and the insulation are exposed. Save the braid, bend it and flatten it, mark it and wrap it around the existing braid. Wear it to make a conductor to earth. Fold and weld a tab with hole in the braid, then cut it open so that it fits over the stud at the IEC / EIA connector.

Radio World: Home-made adapter can get you out of trouble

The braid connection should be covered with several layers of insulation tape. Remove 2 cm of insulation from the center conductor and flatten the conductors.

Heating the end of the tube piece is very simple using a 325 W welding gun. Place large weld in an area of ​​about 1.3 cm on the outer surface at one end, then place the end of the coaxial RG214 on the welding mound, add more and let cool. Excessive flux is eliminated by scraping effortlessly.

It is necessary to place a 2.5 cm PVC smooth tube top that fits snugly against the copper tube. Cut a notch on one side of approximately 1.3 centimeters wide so that it can be placed around the insulation of the center of the coax.

Some type of transparent RTV sealer can be applied around the tube cap and over the connection to provide a safety margin.

See the close-up of the cable end in Figure 1.

To secure the coaxial to the copper tube, a cable tie was used. Figure 2 shows the adapter mounted to the EIA connector. Since the six stud studs protruding from the EIA connector are not threaded all the way to the flange, several flat washers are used to create the necessary thickness so that the nut fits tightly onto the weld flange.

- John Bisset

Oltra Mirada
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