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Author Topic: connector's and coax question  (Read 3155 times)
KD2BDG
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Posts: 16




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« on: January 10, 2012, 06:11:14 PM »

So I'm in the process of putting together a base station. 2m. I bought a fairly older model radio a radio shack HTX 242. I think it will be okay for a first radio. I have a slim jim j-pole made of 450 ohm and i need to connect it to 50 ohm coax. Can i just connect it or should I use a balun. Also the coax going into my radio needs a PL 239 connector. I have searched and I can only find PL 259 and SO 259. No PL 239's.  Any ideas?
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KC1MK
Member

Posts: 24




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« Reply #1 on: January 10, 2012, 09:42:44 PM »

If the J-pole is cut to the proper length, you can connect 52-ohm coax directly to the J-pole.

Your radio has an SO-239 connector for the RF output/input. The proper mating connector for the coax is a PL-259.

Good luck and enjoy the HTX242!

73,
Jeff, KC1MK
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K1CJS
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Posts: 6034




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« Reply #2 on: January 11, 2012, 06:35:54 AM »

A j-pole has a 50 ohm impedance because it uses a matching stub.  A balun is not needed.  Neither are the connectors at the antenna end--unless you plan to put another antenna up in the future.  If you do, it may be wise to use a standard connector at the antenna, and a PL259 connector at the end of the coax.  PL259 connectors will mate with SO239 sockets.

The most popular RF cable plug and chassis-mount socket in use by the ham radio industry are the PL-259 (plug) and SO-239 (socket). The PL-259 can be used with large diameter coaxial cable, such as RG-8/U and RG-9/U, and the smaller diameter RG-58/U and RG-59/U with the UG-175/U and UG-176/U adapter sleeves.
« Last Edit: January 11, 2012, 06:42:52 AM by K1CJS » Logged
N4KD
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Posts: 134




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« Reply #3 on: January 11, 2012, 08:30:09 AM »

Even though a j-pole is an antenna with a 50 ohm impedance, it is not a balanced antenna. If you find that RF currents flow back into the shack along the braid. If you do, a 1:1 choke balun is what you need. Put it right at the antenna. At 144+ MHz, it doesn't take too much RF to be over the FCC limits for exposure. With a HT and low power, you shouldn't need the choke balun, though.

Dave, N4KD
« Last Edit: January 11, 2012, 08:44:09 AM by N4KD » Logged
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