Glenn, Bob and all, What constitutes a good utility ground or a protective lightning ground will not always (you can substitute usually) provide an effective RF ground. See Vic Rosenthal's posting today on this same subject.
For example: Consider that a good RF ground can be provided by a properly tuned counterpoise wire - an electrical 1/4 wavelength long and open at the free end (just like half of a balanced dipole) and separated from earth along its entire length. The near end will present a low impedance at the frequency the wire is tuned to and thus presents a good RF Ground. This near end can be (should be) attached to the tuner (or transceiver) grounding point to provide the RF ground - THE CHASSIS SHOULD ALSO BE CONNECTED TO THE AC MAINS AND LIGHTNING PROTECTIVE GROUND at the same point. The point here is twofold: 1) Each type of ground will have different characteristics, and 2) An RF ground need not have any relationship with what we normally conceive as 'ground' - the British commonly use a separate word - 'earthing' which I believe helps keep the distinctions separate and a bit closer to correctness - earthing is good for AC, DC and lightning grounds, but may or may not have any relationship to an RF ground. I doubt that a Ufer ground would serve as a good RF ground, although it may do so at some particular frequencies - I would want to test it before depending on it. 73, Don W3FPR > -----Original Message----- > > Hi Glenn > Seems a lot of work for a relatively simple rf ground. > Why not just take a piece of copper tubing and lay it in a shallow trench > and bond your ground wire to it? > RF doesn't penetrate the ground very far, so a deep trench wouldn't be > needed. > > Glad to see you're still around. Haven't heard you on in a while. > 73, Bob N6WG > > -----Original Message----- > > I recently up graded my house electrical panel from 100 to 200 amp > service. In order to do the up grade I had to install a Ufer ground > which was 20 feet of bare #4 copper wire in cement. Our local code > allowed a 10 foot run of wire in a U shape in a 9 inch wide trench. The > wire had to be 3 inches above the dirt 3 inches from the side of the > dirt 3 inches between the wires and three inches away from the dirt on > the other side of the trench. That allows for 3 inches of cement all > around the bare copper wire. The more I found out about Ufer grounds the > better they seem to be to me. The PH factor in the cement and the fact > that the cement never completely dries out and retains moisture make it > an excellent ground. > > This leads me to my question. Is anyone out there using a Ufer ground as > a counterpoise or to ground their tower and station? This seems way > better than the old ground rod pounded in the dirt. Any comments would > be appreciated. > > -- No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.323 / Virus Database: 267.8.15/49 - Release Date: 7/14/2005 _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
