Topband: Chassis Bonding

[Tom W8JI]

Jim,

Asking customers to modify equipment, which might also include adding ground 
studs to computers, is just silly when the entire issue is solved with audio 
line isolation in the interface line.



> There is no problem with V- bonded at load equipment (the rig). The 
> problem is bonding at the power supply, and that is EASY to fix -- 
> indeed, many (most?) power supplies are built  either with V- NOT bonded, 
> or with nothing chassis-referenced and a removable jumper at the output. 
> All Astron supplied I've looked at are built this way -- indeed, all I've 
> looked at had the bond to the mounting stud of terminal strip that was 
> insulated from the chassis by paint. So they were NOT bonded, and neither 
> was the green wire, which went to the same lug.
>>

>> We cannot force the world to do things that are difficult, expensive, 
>> and/or inconvenient.
>
> Huh? Ground bonding is required by LAW in most of the civilized world, and 
> part of the National Electric Code that has been adopted as an electrical 
> Building Code almost everywhere in the US. And in those places where NEC 
> has not been adopted directly it is the model for local codes (LA, 
> Chicago, for example).  Beyond that, it is good engineering practice.

At risk of being repetitious, neither a manufacturer nor an author can force 
customers to do things that are inconvenient, expensive, time consuming, not 
commonly done, or difficult, just to save a $2 transformer.

The manufacturer, or the person giving advice, would have to be willing to 
take the heat for saving the $2 when the savings makes the entire system 
more critical, difficult, complicated to implement, and/or risky to 
equipment or performance.

There is no advantage to eliminating the transformer, other than cost (and 
some people in the audio-fi world don't like transformers).
There is considerable worry and risk. It is actually pretty silly to not 
isolate the line, unless it is all mounted in one metal cabinet rack!

I can 100% assure everyone that no manufacturer in their right mind would 
put an interface product out with common-connected unbalanced lines. If we 
think about it, we even isolate unbalanced Beverage antennas from unbalanced 
coaxial lines! This is how good system planning works in the real, 
imperfect, world we live in. We might want, dream of, or demand, a perfect 
world with everyone and everything all lined up the way we want, but it 
virtually never happens.

Good engineering plans around the imperfections.

73 Tom