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Author Topic: RG6U 75 ohm 18AWG Coax question  (Read 1300 times)
W1JKA
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Posts: 1821




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« on: April 26, 2013, 04:12:04 AM »

 I was recently given about 200 ft. of this coax.Is there any major problems using this for low power HF feedline use with Dipole or or ground mounted 1/4 wave vertical antenna experiments and any effect if you do or do not use a tuner with it?
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W5CPT
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Posts: 561




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« Reply #1 on: April 26, 2013, 04:39:15 AM »

Definitely use it. There is a slight impedance mismatch but it will not make much of a difference.

Clint - W5CPT -
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KF7CG
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Posts: 875




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« Reply #2 on: April 26, 2013, 10:35:28 AM »

You will find that its loss characteristics are very good at HF. The mismatch between 75 ohms and 50 ohms is only 1.5 which is often ignored by the autotuners in many of the rigs. Also, the nominal impedance of a half wave dipole is 72 ohms, that sounds like a good match to me.

You may have some trouble connecting it with the UHF style connectors and need an adapter for the Type F connectors that are normally used with this type of coax. A female Type F barrel connector a piece of stiff 18awg wire and a PL259 can be used to build an adapter.

Solder one end of the wire to the center pin of the PL259. Insert the other end (trimmed to where it doesn't go too deeply) into one end of the barrel connector and then thread (cross threading expected) the barrel connector into the adapter threads of the PL259 shell. Presto, you now have an F to 259 adapter.

KF7CG
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W1JKA
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« Reply #3 on: April 26, 2013, 01:30:57 PM »

Thank you both for the info,it's a go.
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