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Author Topic: Adding 15' of LMR-400 antenna lead  (Read 486 times)
K1KIK
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Posts: 12




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« on: August 22, 2009, 06:45:33 AM »

I have a 75 foot roll of LMR-400 and need to go about 90 feet with it.  Will it cause any problems if I screw in a 15-20' length of coax.  The total length is going from a multi-band dipole to a FT-950 (100 watts max)and I have both an internal and external antenna tuner. Thanks.
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K8MLM
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« Reply #1 on: August 22, 2009, 07:15:02 AM »

Shouldn't hurt any thing at lower frequencies, but more feed line than you need and barrel connectors are asking for loss at higher frequencied; e.g. 10 meters.  Make sure you have the connection water proofed and add some strain relief.

73

Bob
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K5LXP
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« Reply #2 on: August 22, 2009, 07:21:24 AM »

Extending the length of coax with more of the same kind isn't a problem.

Feeding a multiband dipole with coax is the problem.


Mark K5LXP
Albuquerque, NM
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W4VR
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« Reply #3 on: August 22, 2009, 07:23:02 AM »

Should not cause any problems...I've done exactly this in a couple of antenna installations.  Spray the barrel connector and PL-259's with an anti-oxident and wrap the entire assembly with Coax Seal or Silicone Tape.
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KK7KZ
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« Reply #4 on: August 22, 2009, 08:05:57 AM »

As Mark said, if it's a fan dipole, no problem. If it's a single wire multiband dipole, the power lost to the barrel connector is peanuts compared to the power lost feeding a multiband dipole with coax.
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K1KIK
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« Reply #5 on: August 22, 2009, 11:10:12 AM »

OK. Thanks for the info.  I will add a second string and seal it with coax sealer.
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KB1LKR
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« Reply #6 on: August 22, 2009, 11:23:30 AM »

You could also use a male and a female cable end N connector vs. two UHF males and a barrel connector, though at HF the difference, other than better weather seal w/ the N, is probably moot.
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W5RB
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« Reply #7 on: August 22, 2009, 11:27:01 AM »

To state the obvious, which nobody has yet , the splice , all things being equal , should go at the end near the ground .It may give years of trouble free service , but when you need to get to it, it's better if it's NOT up the tower.
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