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Discussion Starter #1
Hi;
I am installing a VHF Amateur radio antenna on the side of my house.
I was shocked to find that #6AWG THHN would cost me 0.80/ft, and HD didn't have any bare copper conductor.

What would you think of using NM Romex cable with all three conductors tied together as the ground for the antenna.
Considering I paid only about $25 for 250ft 14/2 Romex, that would be a whole lot cheaper.

I realize that running NM (not UF) on the outside of the house is not code, but considering that this would be a ground conductor only, I don't think it really matters.

I'm going to keep looking for less expensive ground conductor, but in the mean time, what do you guys think of my idea?

Thanks

FW
 

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How many feet do you need?

If money is that tight you can find someone to sell you some scrap.

Hell I'd GIVE you some scrap just for the satisfaction of knowing that a job was done with some degree of professionalism.
 

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Discussion Starter #3
I need about 50 ft to get from the antenna mast to the SE ground at the electrode.
I'm going to check my local electric supply, as someone said HD often has great prices on Romex, etc only to make it up by fleecing you for THHN and similar.

I'll also check Ebay.

FW
 

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I might have over reacted. :laughing:

Seriously, use the romex. It's copper wire, What's the worst that can happen? Maybe someone will take a pic and post it here :laughing:

Just strip the conductors insulation a few inches and twist em together.
 

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Seriously, use the romex. It's copper wire, What's the worst that can happen? Maybe someone will take a pic and post it here :laughing:

Just strip the conductors insulation a few inches and twist em together.
This is for grounding a fault (lightning, specifically). If three separate conductors were a good idea it would be done all the time. I'd think that the fault current will not necessarily distribute itself evenly over the three grounding conductors on its way to ground, and the individual conductors aren't going to be able to handle it.

I say why risk it. :no:
 

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Discussion Starter #6 (Edited)
This is for grounding a fault (lightning, specifically). If three separate conductors were a good idea it would be done all the time. I'd think that the fault current will not necessarily distribute itself evenly over the three grounding conductors on its way to ground, and the individual conductors aren't going to be able to handle it.

I say why risk it. :no:
I think you have a point. Under static conditions, where the current does not exceed the ampacity of the combined conductors, there should not be a problem combining separate conductors. But, with lightning, the actual current may well exceed the ampacity of the combined conductors, and heating plus resistance of the twist could, at least in theory cause an imbalance of current between conductors.

In reality, I am allowed to use up to #10 copper for the ground conductor of the antenna. I have set my mind on #6, because I think it is what is recommended, and most often used by Amateur radio stations.
If I can find a reasonable price on #6, I will certainly use it.

I am currently strapped for cash, having already spent enough on the project, but I won't complain about the difference in cost of #10 or #6, as long as I can get a decent price on it.
I think HD's price of 0.80/ft is robbery.

FW
 

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Here's a thought. And I'll probably get reamed for this but, if you are so strapped for cash, maybe you could buy five sticks of 1/2" EMT and use them for the ground? Put a ground clamp at each end and use a short piece of #6 to make the connections.

OK, I'm ducking...
 

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What about soldering the ends of the conductors together at each end of the romex to add an electrical as well as mechanical bond to the 3 conductors?

"I think HD's price of 0.80/ft is robbery" Supply and demand- Economics 101 LOL!!
 

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IF such a scenario was acceptable, it would be so stated in the Code.

You only have to use a #10 copper wire for that mast ground, if you think that using a #6 costs too much. :whistling2:
 

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Discussion Starter #15
1/2" EMT is around 1/4 the price of #6 copper at $0.80/ft. Why not practical, obstructions?
My first thought is that EMT running down the side of the house would be un-aesthetic, but on second thought, maybe no worse than #6 THHN. If I painted it to match the house, it would mostly go unnoticed.

1/2" EMT is only $1.65 for 10ft at HD, but what about the fittings?
I would need one 90 elbow. I suppose a standard elbow is cheap, but what if I ever wanted to really use this conduit for power?
Would code allow me to run say 3 #12 THHN (hot, neutral, ground) through the conduit and still use it as the antenna ground?
And then if I were to use it for power, I would need to weatherproof it. Those fittings are more expensive.

Then, maybe I'm going a lot further than I need to go. I already have a wall inside the house where I have pulled several new branches over the past couple of years, so I shouldn't need any more.

Thanks for all your help on this. It should be worth all the trouble once it's up.

FW
 

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At risk of hijacking this post, why is lightning rod cable braided?

I think that KC may be on to something! Its been found that electrons in a conductor travel in the 'skin' rather than in the core.
In this case, is it possible that a back EMF could be generated in adjacent conductors, resulting in resistance to current flow?
 

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This is an interesting question. My concern would be that the ground would fail at the point where the three wires branched to their individual conductors. I would be concerned that the current would burn through the individual wires when they were subjected to the full current of the lighting strike. I am not an electrical engineer, but this seems a valid concern.
 

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At risk of hijacking this post, why is lightning rod cable braided?

I think that KC may be on to something! Its been found that electrons in a conductor travel in the 'skin' rather than in the core.
In this case, is it possible that a back EMF could be generated in adjacent conductors, resulting in resistance to current flow?

It is a fat braid because of skin effect like you said. At DC, there is effectively no skin effect. At 60hz skin effect is only an issue with very large conductors (significantly larger than 4/0)... at say 10khz, skin effect dominates and current is only carried in the very outer part of a conductor.

The rapid rise in current is effectively a "high frequency"... And skin effect happens primarily at higher frequencies.

So even though it's technically a DC flow, you don't want to present an instantaneous impedance to the rapid rise in current, so you need a lot of surface area to carry the current on the skin.
 
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