[Elecraft] Bonding

Don Wilhelm w3fpr at embarqmail.com
Tue Jan 19 22:07:46 EST 2010


Jim (and all),

I believe we are both correct - and "it all depends...".
The variety of "sneak" ground paths  from one piece of equipment to 
another are numerous indeed (pin 1 problems are another source of 
trouble, and may confuse the real source as well).  A star grounding 
system is the first place to start (IMHO), but additional bonding may be 
helpful in some situations.  There is no one right answer - it all 
depends on your particular installation and your antenna installation.  
Is the problem RF or is it from ground current coupling from one piece 
of equipment to another?  How to treat a particular problem will depend 
on the answer to that question.  And, if it is caused by ground 
currents,  the method to properly reduce them will vary from one 
installation to another (bonding the offending two pieces of equipment 
by a low impedance path may be required).  A good starting point is in 
Jim Brown's website information, but the total answer is station to 
station dependent - this is not a case where "one size fits all". Some 
investigation along with a bit of trial and error may be required.  
Consider that "sneak" grounding paths are just what that indicates - 
they are unwanted and unlikely to be obvious to casual observations.

73,
Don W3FPR

Jim Brown wrote:
> On Tue, 19 Jan 2010 17:55:04 -0500, Don Wilhelm wrote:
>
>   
>> I agree too, but would like to clarify that the "bonding" should not be 
>> a "helter-skelter" connection of one piece of equipment to another.
>> The most effective way of accomplishing that is to connect each piece of 
>> equipment in the shack to a common point (which may be optionally 
>> grounded or connected to a low impedance for RF (mother earth ground is 
>> only for lightning protection and personal safety, not RF grounding).
>> That type of bonding connection is often referred to as a "star" 
>> configuration - as opposed to a 'daisy-chain' where the connection is 
>>     
> >from one piece of equipment to another.
>
> There are really at least three different issues being addressed here. 
> One of them is bonding for lightning protection and power system safety. 
> The bonding that I was talking about to solve this issue is specifically 
> aimed at solving what I suspect are pin 1 problems in the interconnected 
> equipment. So the function of the bonding I recommended is to provide a 
> low impedance path from chassis to chassis, so that RF is more likely to 
> flow on the bonding conductors, chassis to chassis, than on interconnect 
> cables (audio and control) into the circuit board and into the circuitry 
> (by the pin 1 problem). That's also the reason for ferrite chokes on the 
> interconnect cables. 
>
> I certainly agree that a very low impedance bond of all equipment to a 
> single point is a good idea. BUT -- I don't want the path from computer 
> chassis to rig chassis to be any longer than necessary -- I don't want it 
> to go to the center of the star and back, for example. I've seen this 
> "star" approach implemented with a piece of copper pipe that runs along 
> the back of a radio bench, with a dozen or so wires connected at points 
> that are 6-10 ft apart. By contrast, my laptop sits on my operating bench 
> between two K3s, and there's a short piece of #10 braid going to both 
> rigs. The third reason for bonding is to minimize the audio voltage from 
> chassis to chassis that is caused by leakage current in the power system, 
> and that gets added to signal for any unbalanced connection between 
> equipment. By bonding that equipment with big copper, we minimize that 
> voltage (and divert the current away from pin 1 problems as well). 
>
> As for my lightning protection bonding -- THAT'S where I implement the 
> star. The rigs are bonded to the power outlet green wires with a short 
> piece of braid (outlets are just below the bench). The power outlets are 
> bonded to the coax entry panel, also just below the bench, which in turn 
> goes to a half dozen ground rods. There's also a lot of coax routed 
> through various switches to the coax entry panel (with feedthrough 
> arrestors). That provides a DC bond, but those coaxes have a lot more 
> inductance compared to the short braids. The power outlets run in EMT 
> (thinwall steel conduit) back to the power panel, which has three ground 
> rods of its own, on the other side of the small building that houses my 
> shack, and some #4 copper runs around the perimeter of the shack to tie 
> the ground rods together that way. 
>
> Does this clarification allay your concerns?
>
> 73,
>
> Jim K9YC
>
>
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