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Author Topic: long wire RF  (Read 1010 times)
W4CLQ
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Posts: 18




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« on: July 22, 2004, 07:36:00 AM »

I plan on using a random wire due to my housing situations an antenna and everything I read says not to bring the RF from the wire into the shack.  How much wire is too much?  I plan on running it for a tree outside into the window and on to the tuner.  Is there another way to connect this to my tuner?  I will have about 5’ or so inside the shack.  Thanks

SS
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W7DJM
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Posts: 1




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« Reply #1 on: July 22, 2004, 11:01:14 AM »

First, you are not talking about a "long wire" you are talking about a "random wire."

You might want to look for a different solution, not knowing your layout, I know not what.

A random wire is, generally speaking, a pretty poor performer, and is subject to the worst of RFI situations, because the antenna radiates the first inch that it leaves the tuner.

Back in the days when some of us were in the old "shack" in the back yard, didn't have TOO many TV's (or could just shut them off) and no computers or touch lamps, etc, this was not such a problem.


Last, because it radiates the entire length of the antenna, that means that your RECEIVER will also pick up noise from the very same TV's lamp dimmers, cell phone chargers, computers. etc, etc,


One solution might be coax on the ground, out to a remote mounted auto tuner?

ANY chance to get ladder line in? (or tv twinlead)
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N4VNV
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« Reply #2 on: July 22, 2004, 12:02:19 PM »

It's a shame people don't pay attention. You stated "Random Wire" in your explanation. Now, that said, I have been running random wire antennas off and on for 50 years. I've had really good luck with them in some locations and poor in others.(I mean different houses, I'm retired military and moved a lot) If there is a cast iron fix for grounding one of these systems, I don't know what it is. In other words, this is not the easiest antenna in the world to live with. BUT I love them because they are low maintenance and inexpensive. In each location it took a different grounding setup to get the desired results. Use your imagination, you will probably get an answer quicker than asking. Again, because there is NO ONE SOLUTION.
Currently, my ground is the ductwork of my air/heating system in my home. It is a #12 gage stranded & coated wire, 180' long and up 50' laying on three tree tops. It has been working "GREAT" on all HF bands for me these last three years. Be advised, when you get one of these working well, it makes the guys that spent big money mad. Notice how many ragchews are cut short when they find out what your antenna is.
73's and good luck.
Larry
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N4VNV
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« Reply #3 on: July 22, 2004, 12:05:26 PM »

In paragraph two, the 12 gage wire is the antenna itself. Not the ground wire. I use a 4' Lg, 2" wide braided ground strap to the ductwork. And I have about 5' of the antenna wire in the house.
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W7DJM
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« Reply #4 on: July 22, 2004, 01:23:47 PM »

"It's a shame people don't pay attention"

Yes, it certainly is.  The title he used for this post is "long wire RF."   I was merely pointing this out.

"Notice how many ragchews are cut short when they find out what your antenna is"

Funny, I never noticed this, myself.  When I was recovering from a bad auto accident, in temporary quarters, the only thing I had up was an 80 dipole, with crude switches to shorten it to 40 meters.

IT WAS FED with an electrical extension cord about 40 years old, and I managed to work Italy on the thing on day on 15 meters.


""Currently, my ground is the ductwork of my air/heating system in my home.""


I certainly would discourgage this.  There is no reason to believe that the ductwork is electrically sound, and may cause "external mixing" problems at loose joints.
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W4CLQ
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Posts: 18




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« Reply #5 on: July 23, 2004, 10:01:11 PM »

Can't we all just get along?

Thanks everybody,
SS
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N4ZOU
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Posts: 340




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« Reply #6 on: August 04, 2004, 10:14:28 AM »

I have run random and long wire antennas for portable operation for years. One solution for shack RF is to simply connect a length of RG-8 coax to the wire antenna element. This gets the shack end of the wire element out of the shack. Length is determined by the requirements of your shack layout and by how well your antenna tuner can handle the high or low impedance produced on different bands and frequency. Cut the RG-8 coax to the length required getting it out of the shack and having it supported properly. The coax can't have any strain on it from the wire element. Next simply check the bands you plan to operate on. If you have a problem with your antenna tuner simply add or cut a foot or two and try again. You will find a length that will work. Also do not use a smaller size coax like RG-8X or RG-58. There will be high current or voltages in the coax on different bands, which the smaller coax will not be able to handle. A good random or long wire antenna will be longer than a 1/2 wavelength on the lowest band you plan to operate on. This will lesson the ground requirements. With the wire element longer than a 1/2 wavelength the ground is there just for safety and no longer is it required as a part of the antenna system making the antenna very efficient.
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K8AG
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Posts: 352




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« Reply #7 on: August 11, 2004, 12:20:52 PM »

Hi Steve,

Everybody has opinions and you could spend the next 5 years designing the optimum wire for your situation.  My advice is to get a wire up.  Put as much wire as high as you can and use a good tuner to make it work.  Yes a better antenna will make a big difference.  But wire is fairly inexpensive and with an antenna up, you can spend time designing the next edition, while still being on the air.

See you on the air.

73,

JP, K8AG
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