OT- Coax for ground wire?
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I have learned quite a bit about grounding from K9YC and others on the list over the years and thank you all for making my shack a better place.
I have been tying together outside grounds where antennas enter the house back to the service ground as part of my improvements and have run out of heavy wire to do so. I do have some old RG 8X or 213 around and have been thinking about using that for grounding. My questions are: 1. Good idea/bad idea? 2. Should I use just the shield or is there any downside to bonding the shield and center conductor at each end? Thanks in advance for any advice offered. 73, Joe, W8JH K3 1713, KPA 132
73,
Joe, W8JH K3s, KPA 500, KAT 500 and KX3 happy user. |
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On 10/21/2011 12:25 PM, Ron D'Eau Claire wrote:
> For RF, you want the lowest possible inductance in the ground lead since > inductance has reactance and reactance is what you do*not* want. Yes, BUT -- the principal function of the EARTH connection is lightning safety. With any antenna that loads like a long wire and ends in the shack, the "ground" wire is part of the antenna unless it has been decoupled from the "ground" wire by a lot of radials that end in the shack. Further, the other end of that wire goes to lossy earth, and the equivalent resistance of the earth connection reduces the power that gets radiated -- UNLESS there are radials. Bottom line -- low inductance is important for lightning safety, but it's primary effect on behavior of a long wire antenna (including inverted L, Tee vertical) is to lengthen the antenna a bit and add loss. And yes, the braid of coax makes a nice ground conductor. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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And that my friends is why the broadcast stations have extended amounts of "sheet" copper tying everything to ground that should be. IMHO.
Mel, K6KBE ________________________________ From: Ron D'Eau Claire <[hidden email]> To: [hidden email] Sent: Friday, October 21, 2011 4:07 PM Subject: Re: [Elecraft] OT- Coax for ground wire? I think Jim accidentally reversed his meaning about ground lead inductance. Lowering the inductance of the ground connection does *not* lengthen the effective radiator or "add loss". Allowing the ground system to be part of the radiator by letting the ground lead have significant inductance and so add to the overall length of the antenna system may well increase losses and promote coupling to house wiring, etc. That's good reason to use a low-inductance ground connection. When running an end-fed wire as I do, it's useful to keep the rig chassis at a low RF potential. If the rig is allowed to have significant RF voltage on it (as when the feed point of the wire is near a voltage loop), the rig adds my body to the active antenna, changing the tuning. Also, significant RF voltage floating around the DC supply chassis (because it's connected to the rig) can do weird things to the voltage regulation if a junction in the regulator starts rectifying the RF. In my case the copper sheet terminates in an RF ground system that enters through the wall a few feet from the operating position, so extending the sheet to where it enters ensures that the entire copper sheet stays at a very low RF potential at all times, and having the sheet extend behind the equipment allows very short ground connections to each chassis, keeping everything at the same low RF potential. 73, Ron AC7AC -----Original Message----- On 10/21/2011 12:25 PM, Ron D'Eau Claire wrote: > For RF, you want the lowest possible inductance in the ground lead since > inductance has reactance and reactance is what you do*not* want. Yes, BUT -- the principal function of the EARTH connection is lightning safety. With any antenna that loads like a long wire and ends in the shack, the "ground" wire is part of the antenna unless it has been decoupled from the "ground" wire by a lot of radials that end in the shack. Further, the other end of that wire goes to lossy earth, and the equivalent resistance of the earth connection reduces the power that gets radiated -- UNLESS there are radials. Bottom line -- low inductance is important for lightning safety, but it's primary effect on behavior of a long wire antenna (including inverted L, Tee vertical) is to lengthen the antenna a bit and add loss. And yes, the braid of coax makes a nice ground conductor. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by W8JH
Most sheet metal shops can sheer copper sheets into almost any width one
would want, and the cost is reasonable. I had about half of a 4 x 8 sheet sut into 1 and 2 inch x 4 foot strips several years ago and that's used throughout my station's grounding system. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Copper strap is better for lightning protection grounding than braid
(more surface area). DX Engineering and GeorgiaCopper are two sources that I know about, there are certainly others (use Google). 73, Don W3FPR On 10/21/2011 8:25 PM, Rose wrote: > Most sheet metal shops can sheer copper sheets into almost any width one > would want, and the cost is reasonable. I had about half of a 4 x 8 sheet > sut into 1 and 2 inch x 4 foot strips several years ago and that's used > throughout my station's grounding system. > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Rose
Most sheet metal shops can sheer copper sheets into almost any width one
would want, and the cost is reasonable. I had about half of a 4 x 8 sheet sut into 1 and 2 inch x 4 foot strips several years ago and that's used throughout my station's grounding system. 73! Ken - K0PP [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jim Brown-10
On 10/21/2011 4:07 PM, Ron D'Eau Claire wrote:
> I think Jim accidentally reversed his meaning about ground lead inductance. > Lowering the inductance of the ground connection does*not* lengthen the > effective radiator or "add loss". No, I didn't accidently reverse my meaning. You missed my point. ANY length of lead in the "ground" wire adds inductance. The difference in inductance between a #22 wire and RG8 isn't enough to matter. Repeat after me (or write it 100 times on the blackboard). "A connection to earth has NOTHING to do with RF ground, nor does it cure RFI issues, nor does it make an antenna work better. What DOES matter (a lot) is the connection of a cable shield to the shielding enclosure of equipment." 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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