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PROJETO DE ANTENA J DE VHF 144-148 MHZ

THE J POLE ANTENNA

THE J-POLE ANTENNA IS A VERY USEFUL ANTENNA IN SITUATIONS WHERE A DC GROUND AND VERY LITTLE GAIN IS REQUIRED. THE REASON THAT I LIKE THE ANTENNA IS THAT IT IS SIMPLE TO BUILD, STURDY, AND VERY EASY TO TUNE. A FEW THINGS SHOULD BE DONE THOUGH IN ORDER TO PROLONG THE LIFE OF THE ANTENNA.

1. CLEAN ALL COPPER FITTINGS WELL IN ORDER TO INSURE A SOLID MECHANICAL AND ELECTRICAL CONNECTION. A POOR CONNECTION CAN MEAN THAT THE ANTENNA WILL "SELF-DESTRUCT" IF IT IS PUT OUT IN THE WEATHER AND WIND.

2. USE A STRANDED WIRE TO CONNECT THE CENTER PIN TO THE SHORTER LEG ON ANTENNA. I HAVE USED SOLID WIRE IN THIS AREA AND AFTER A SHORT AMOUNT OF TIME THE SOLDERED JOINT WILL CAUSE THE THE WIRE TO BREAK FROM THE CONSTANT FLEXING OF THE PIPE IN THE WIND. THE STRANDED WIRE WILL FLEX A SLIGHT BIT SO THAT IT WILL NOT JUST BREAK.

3. SOLDER AND BOLT THE COAX CONNECTOR TO THE ANTENNA. BOTH OF THESE JOINTS WILL WORK TOGETHER TO HELD INSURE A STRONG MECHANICAL AND ELECTRICAL CONNECTION. DO NOT USE A RADIO SHACK BRAND SO-239 CONNECT AS THEY ARE BASICALLY JUNK. THE CENTER INSULATIVE MATERIAL WILL NOT WITHSTAND THE TEMPERATURE IN THE OUTSIDE AND WILL DEGRADE RAPIDLY. TIN AN AMPENOL BRAND CONNECT WITH SOLDER AND THEN TIN THE PIPE. AFTER THIS HAS BEEN DONE, BOLT THE CONNECTOR WITH THE TINNED PIECES FACING EACH OTHER AND THEN WARM THE CONNECTOR WITH A SMALL TORCH. AFTER THE SOLDER HAS SET, IT WILL BE ROCK SOLID.

4. DON'T SKIMP ON COST AS I HAVE ON SOME ANTENNAS, BUY STAINLESS STEEL HARDWARE TO BOLT THE ANTENNA DOWN. IF YOU EVER HAVE TO MOVE THE ANTENNA OR RETUNE THE ANTENNA YOU WILL THANK ME FOR THIS HINT.

5. CAP THE PIPES AND PAINT THE ENTIRE ANTENNA. PAINTING THE ANTENNA WITH A NONMETALLIC PAINT WILL ENSURE THAT THE ANTENNA WILL LAST FOR YEARS TO COME. MAKE SURE TO DRILL A SMALL DRAIN HOLE IN THE BOTTOM LEG OF THE ANTENNA SO THAT ANY CONDENSATION CAN DRAIN OUT.

 


VEJA AQUI UMA FORMA FÁCIL DE VOCÊ CALCULAR A SUA ANTENA JOTA, EM VÁRIAS FREQUÊNCIAS, ONDE BASTA VOCÊ DIGITAR A FREQUÊNCIA A QUE VAI QUERER OPERAR, E CLICAR NO BOTÃO DE CALCULAR. TAIS ANTENAS ESTÃO PRÉ CALCULADAS PARA USO DE TUBO DE 1/2" DE DIÂMETRO.

FREQUÊNCIA

SEÇÃO INFERIOR

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SEÇÃO SUPERIOR

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SEÇÃO MATCHING

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