[Elecraft] I didn't realize what you meant (was RE: WARNING! WARNING! WAR...

[AJSOENKE at aol.com]

In a message dated 11/23/2007 12:13:55 P.M.  Pacific Standard Time, 
M0XDF at Alphadene.co.uk 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
 



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