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Author Topic: Coax Cable  (Read 2798 times)
W3EK
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Posts: 10




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« on: September 02, 2011, 07:22:46 AM »

       I need help with the following. Thanks for reading this and any help.
I am putting up a Comet CH-250B vertical. I will be running from 5-150 watts. I need to run/ fish the coax from a garage to house through an existing power line piping that houses both 110v and 220v service. What is the best type of shielded coax to use. The run will be less than 100 feet. I want to stay away from the large RG-8 style coax. Thanks & 73's  Rich W3ECU
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N3WAK
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Posts: 273




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« Reply #1 on: September 02, 2011, 09:28:08 AM »

Rich: 

If you're going to use your vertical only on HF, RG-8X is just fine if your SWR is reasonable--e.g., 3:1 or better.  For 6 meters, I'd use RG-213 or Davis RF Buryflex, since RG-8X has too much loss at VHF. 

Also, I'm very leery of running coax near "power line piping."  I don't know exactly what you mean by that, but being fatally electrocuted will ruin one's day.  Be careful.  Don't take any chances.  I myself would choose a different route for my coax.   

Here's a coax loss calculator that's very useful:  http://www.arrg.us/pages/Loss-Calc.htm  In addition, there are charts you can find on-line showing the power handling capacity of various types of coax.  This information is also in the ARRL Antenna Book. 

73, Tony N3WAK
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AA4PB
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« Reply #2 on: September 02, 2011, 10:07:07 AM »

In most places it is against code to place coax or other "low voltage" wiring inside a conduit that contains electrical (120/240V) power. The concern is that if somehow the cables get shorted together then your "low voltage" circuit could have 120VAC applied to it.

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K7KBN
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Posts: 2754




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« Reply #3 on: September 02, 2011, 10:13:08 AM »

Rich:  

If you're going to use your vertical only on HF, RG-8X is just fine if your SWR is reasonable--e.g., 3:1 or better.  For 6 meters, I'd use RG-213 or Davis RF Buryflex, since RG-8X has too much loss at VHF.  

Also, I'm very leery of running coax near "power line piping."  I don't know exactly what you mean by that, but being fatally electrocuted will ruin one's day.  Be careful.  Don't take any chances.  I myself would choose a different route for my coax.  

Here's a coax loss calculator that's very useful:  http://www.arrg.us/pages/Loss-Calc.htm  In addition, there are charts you can find on-line showing the power handling capacity of various types of coax.  This information is also in the ARRL Antenna Book.  

73, Tony N3WAK

"Fatally electrocuted"?  As opposed to "shocked"?  "Electrocuted" = "dead".
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73
Pat K7KBN
CWO4 USNR Ret.
KI4SDY
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Posts: 1452




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« Reply #4 on: September 03, 2011, 06:21:09 AM »

If you didn't suspect that this was a bad idea, you wouldn't be asking us. I will confirm it for you. This is a bad idea for three reasons. First, as the others have said, there is the danger of electrocution from the existing electrical power. Second, lightning may come in on the power line and jump off on to your coax or vice versa. Lastly, there is a possibility your coax will pick up power line noise. Then you will be posting about how to get rid of the "mysterious" RFI.  Shocked

I have another question. Why are you running the coax from one building to another, rather than just straight up, from the building that has the radio equipment in it to the antenna? You want to go up, not sideways. A waste of coax and loss of signal.  Wink
 
Don't do it! Find another path to run the coax to the antenna!  Grin
« Last Edit: September 03, 2011, 07:05:56 AM by KI4SDY » Logged
W8JX
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Posts: 5358




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« Reply #5 on: September 03, 2011, 06:29:10 AM »


I have another question. Why are you running the coax from one building to another, rather than just straight, up from the building that has the radio equipment in it to the antenna? You want to go up, not sideways. A waste of coax and loss of signal.  Wink
 
Don't do it! Find another path to run the coax to the antenna!  Grin

I agree. I would not run it with power lines. I suggest directly burying 213 or better coax in ground. 
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K7KBN
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Posts: 2754




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« Reply #6 on: September 03, 2011, 11:05:47 PM »

Reply #3

What you said is not without fault according to the definition of electrocution by Collins English Cobuild Dictionery.

1    verb  If someone is electrocuted, they are accidentally killed or badly injured when they touch something connected to a source of electricity

http://dictionary.reverso.net/english-cobuild/electrocution

Hang loose there Pat.

I went through six different printed dictionaries, all published in the past five years, and twenty online dictionaries.  Of the 26, only that "reverso.net" (which doesn't inspire confidence) agrees with you.  Follow the etymology: the -cute ending is the same with "execute", as in "putting to death".

It's 25 to 1: If you're electrocuted, you're dead.

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73
Pat K7KBN
CWO4 USNR Ret.
W8JI
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Posts: 9304


WWW

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« Reply #7 on: September 04, 2011, 05:55:40 AM »

This just shows how sloppy we are getting, and how anything can be justified on Internet.

I suggest everyone rent  Idiocracy. It explains this.

As for the coax, I would not put the cable from a Comet CH-250B with any wires, low voltage or high voltage. If installed as suggested, it has pretty high common mode RF on the coax.

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K7KBN
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Posts: 2754




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« Reply #8 on: September 04, 2011, 08:30:23 AM »

Hang loose there, Frank.  Roll Eyes
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73
Pat K7KBN
CWO4 USNR Ret.
WB2WIK
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Posts: 20540




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« Reply #9 on: September 05, 2011, 03:31:53 PM »

I see the OP never came back to respond or comment.

However the CHA-250B relies heavily on its performance from having a long vertical conductive mast under it, or a long vertical coaxial transmission line attached to it, since either or both are part of the antenna system.

I've worked with this antenna and found if installed at ground level with coax buried underground it's pretty bad.  On a 30' long conductive mast, it's much better.  On a 30' long non-conductive mast but having 30' of coax attached to it that runs vertically from the feedpoint down to the ground, about the same.

Obviously, either the mast or the feedline or both contributes to performance.
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K2WLO
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Posts: 30




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« Reply #10 on: September 09, 2011, 01:06:57 PM »

"fatally electrocuted" = terminally killed...  Grin
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W3LK
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Posts: 5644




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« Reply #11 on: September 09, 2011, 01:54:53 PM »

I see the OP never came back to respond or comment.

However the CHA-250B relies heavily on its performance from having a long vertical conductive mast under it, or a long vertical coaxial transmission line attached to it, since either or both are part of the antenna system.

I've worked with this antenna and found if installed at ground level with coax buried underground it's pretty bad.  On a 30' long conductive mast, it's much better.  On a 30' long non-conductive mast but having 30' of coax attached to it that runs vertically from the feedpoint down to the ground, about the same.

Obviously, either the mast or the feedline or both contributes to performance.

IOW, a tall, skinny Isotron. Smiley
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