[Elecraft] bonding of grounding systems

[Jim Brown]

This discussion is outside the scope of this Email list.  I'm Vice Chair of 
the Standards Committee of the AES (Audio Engineering Society) on EMC. We run
into these issues all the time,  and I have been doing some extensive
research on these issues. I've published four papers in the last year on this
topic. The short answers are that: 

1) it should not be necessary to do unsafe things to prevent RF interference
in equipment. 

2) There are defects in the way some commonly used cables are manufactured
that significantly increase the coupling of MF a nd HF RF into equipment

3) There are common design errors in equipment that make them susceptible to
equipment

4) #2 and #3 are excited by current flowing on the shields of system wiring
(the cable is acting as a receiving antenna)

5) Stopping the shield current will usually eliminate the RF problems

There are good ways and bad ways to stop the shield current. Unsafe grounding
practices (like you were probably talking about in your meeting)  are a bad
way.  IMO, there is nothing wrong with NEC as written with respect to
grounding, and certainly not with the requirement that all grounds be bonded.


You can download my AES papers at www.aes.org. They cost $10 each if you're a
member of AES, $5 each if you are not. I don't get any of that money. The
papers describe nearly a year of research, there is lots of good data, and
the writing is quite accessible (no math). Some of that research is changing
the way that cables are made, and the way audio gear is designed and built. 
There are direct applications to ham radio -- in fact, I am seeing some of
the same design problems in ham gear.  

Jim Brown  K9YC


On Sun, 23 May 2004 15:54:08 -0400, kce wrote:

>For safety sake especially concerning circuit faults and lightning,
>systems should be bonded, but 7 years ago during a meeting we had a big
>discussion about isolating grounding systems pertaining to RFI problems.
>One of the local A.M. stations had increased transmitter power with the
>result of wild RF running all over the place.