[Elecraft] [OT] K9YC's Serial Cable question

[Don Wilhelm]

  I do not doubt about Jim's advice, but I sense that only a few are 
willing to replace those computers or USB to serial adapters that are 
classified by Jim's definition of "bad equipment" with good alternatives 
(BTW, I agree with Jim on the "bad equipment".  Many DO need a signal 
return connection to pin 5 or they will not work.

Jim has given you the trouble signs, so if your equipment needs the 
return path to be pin 5 rather than the shell, by all means connect it 
there - but do heed Jim's cautions about common mode noise.

If you want to build a cable that meets both requirements, use shielded 
CAT 5/6 cable and wire it as Jim suggests - that will work in all cases.

73,
Don W3FPR

On 6/7/2011 4:57 PM, Jim Brown wrote:
> It may work without RF present, but it won't "work" if it couples hum,
> buzz, or RFI. I've seen RFI so bad that it shuts the computer down --
> that's how this cable came to be developed!   I'm sticking with my
> original advice. Common mode current on signal cables is one of the most
> common causes of hum, buzz, and RFI.  We don't want that current to go
> to the common bus on the PC board, we want it to go to a ground plane,
> grounding star point, or a shielding enclosure. That's why I'm so
> insistent about this.  Equipment that does not allow proper wiring
> techniques is BAD equipment, and should be avoided.
>
> 73, Jim K9YC
>