single ground point questions
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| Nov 5th 2016, 00:47 | |
K7WXWTotal Topics: 0 Total Posts: 0 |
I am a relatively new ham even if I am a fairly old electrical engineer. I hold a General ticket (on Sunday I will take, and hopefully pass, the Extra quiz). I've been working the 2M and 70cm bands with portable equipment while I figure out a base station design I can use to work HF/VHF/UHF. My base station will be in the basement, on the side of the house opposite the electrical service panel. I've been reading through the various QST and other resources on lightning protection, which are quite helpful. That said, here are my three current questions: Is it safe to assume that it is better to locate the entrance for feed lines, etc near the service panel so I can build a good single point ground even though it means longer feed lines (inside and outside the house)? The current electrical panel appears to use a cold water pipe for grounding. I don't imagine I can build decent lightning protection system using that as the single point ground so I am planning on sinking grounding rods. Is that true? If so, does it make sense to re-do the electrical service panel ground to attach to this new ground? 73, bill K7WXW |
| Nov 5th 2016, 02:12 | |
W1VTSuper Moderator Total Topics: 0 Total Posts: 0 |
Yes, from a safety standpoint locating the single point entrance for the feedlines and rotator cables close to the electrical service panel is a good idea. It is generally a poor idea to use the current electrical ground as a single point ground when you consider conducted noise from electrical devices propagating to the ham station. Noise from electrical and electronic devices inside a home generally fall off quickly with distance--it can be worthwhile to locate antennas away from the houses. In most places you will need a permit and inspection if you redo the electrical service panel. Most hams build a high quality single point ground for the station and bond that to the service entrance panel. Ground rods between the two grounds typically reduce conducted noise. Zack Lau W1VT ARRL Senior Lab Engineer |
| Nov 5th 2016, 03:26 | |
aa6eTotal Topics: 0 Total Posts: 0 |
Grounding is a big subject. Too big to do justice here. Keep in mind there are at least 3 separate reasons you want a good ground. Any system is likely to be a compromise between: 1. AC Safety ground. This protects you and your equipment from an AC fault like a short circuit from hot to chassis. The saftey ground will ensure that your AC breaker blows before your house burns down. 2. RF Ground. This ensures against "RF in the shack" when transmitting and excess noise in your receiver. A good RF ground needs to be less than about 1/10 wavelength in length. That can be hard to achieve. 3. Lightning ground. This is the most difficult to deal with. It's hard to convince yourself that you've got a good system until you survive some actual lightning strikes! Provide a very low impedance (low resistance, low inductance) path for lightning currents to follow. Bond all your equipment grounds to a single point ground so they all move together in voltage when there is a big surge current. (Best if you can tie the operator and the entire radio room to that ground. (Build a Faraday cage.) Consult the ARRL Handbook and http://www.arrl.org/grounding for more details. 73 Martin AA6E |
| Nov 6th 2016, 19:42 | |
K7WXWTotal Topics: 0 Total Posts: 0 |
Zack and Martin - thanks for the replies. Given the physical constraints, I probably need to build the single point ground in the front of the house (where the radio room will be) and run a copper line around to the back of the house, where the service panel is located. So... I have more research to do. One more question along those lines: does it make sense to bond that copper line to grounding rods along the run? The total distance will be about 80'. Thanks for your help! 73 Bill K7WXW |
| Nov 6th 2016, 22:08 | |
W1VTSuper Moderator Total Topics: 0 Total Posts: 0 |
W8JI has a grounding page giving his opinions of house different grounding layouts. When I had a station in front the house, and the single point ground in the back of the house, I did not have a ground near the station. I did need about 100 feet of additional coax, compared to just running the coax from the rig to the antenna, but mounting a remote antenna tuner resulted in acceptable feedline losses from 40 through 10 meters. Zack W1VT ARRL Senior Lab Engineer |
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