In a message dated 11/23/2007 12:13:55 P.M. Pacific Standard Time, [EMAIL PROTECTED] writes: No problem Gary and I'm glad we agree on that :-)
Sorry if I didn't make that clear. To try to clarify this.. the basic premise is that anything you attach to you or your kit, while you are building, is bonded to the same point (that's important) and via a 1M ohm resistor lead. I also use dissipative tools, like screwdrivers, cutters etc etc, but that is not really necessary, as long as your body is grounded via a strap. I repeat, this ground MUST be via a 1M ohm resistor (or higher, but better to keep all resistances the same). +++++++++++++++++++++++++++++++ Sorry if I missed something here, and I'm not trying to confuse issues. But, after 40 years in the industry working with the most sensitive of semiconductor devices, the only requirement for a series resistance that I've seen used is in the devices like a wrist strap that were attached to the operators body. The purpose being to protect them from possible contact with power systems that could place the operator in the HV ground path. The 500K or larger resistor was usually adequate to provide a non-lethal warning of somethin amiss. I don't disagree that a big resistor to ground will dissipate a static charge, but most of us would prefer a total ground on the chassis. Otherwise, as I understand it, you still run the risk of setting up a voltage differential that could damage parts. The reasoning is that a static charge will dissipate, being of limited source. But an AC voltage delta between the tip of an Iron and an earth ground could be several volts, depending on the ground point and power system setup. I've seen as much as 40 volts in normal household wiring. The addition of a high value resistance in that circuit could raise the voltage substatially, AND it is a non dissipative source that could fry more than a small semi. The rule I have always applied at home and industrially is: 1) use isolation transformer where possible, 2) use a GFCI protected circuit, 3) establish a common ground point that has the best possible path back to the house ground.( That is usually at the service entrance and should be tested to make sure it works ) 4) use a ground tester to make sure the ground is not open at the outlet. (Testers are cheap and available in most hardware stores) . 5) Make sure the grounds from common point to work surface and chassis are firmly connected - alligator clips always pop off. 6) Wear your wrist strap and avoid synthetic or wool clothing. 7) last and very important - always use an ohmmeter to test the wrist strap and other ground jumpers to make sure they are working. A lot of good hardware can be damaged by an open ground wire. A good OP can be hurt by a bad wrist strap. With the constant flexing of the wrist cables,etc, the wires will break internally and not be noticed, there's no antenna or speaker attached to it to tell you something's wrong. I've done a lot of residential testing in the course of helping run an RFI committee for the local club. We have found many RFI cases caused by bad grounds In home's I've visited over 30 years, I've found about 1 in 10 homes is poorly grounded at the service entrance, and about 1 in 10 has open grounds on outlets. Many result from electrical wiring done by the homeowner without the help of a licensed electrician or city inspector. Judging from the Hams I have met over the years, the SKs I have known, and a lot of the traffic I see on these lists, I have come to the opinion we have many in our midst to with disputable sense of values is some areas. If you can't afford a little coin on Ohmmeters, new wrist straps, GFCIs and a visit from the power company (usually free), you probably don't have adequate insurance to be messing with this stuff. n This isn't where you want to play on the cheap. nuff said' Al WA6VNN **************************************Check out AOL's list of 2007's hottest products. (http://money.aol.com/special/hot-products-2007?NCID=aoltop00030000000001) _______________________________________________ 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
