[CQ-Contest] Optical and galvanic isolation

[Bill Turner]

ORIGINAL MESSAGE:

On Tue, 19 Dec 2006 18:14:03 -0500, "VA3NR" <va3nr at arrl.net> wrote:


>- Regarding audio transformers: I built my original so2r headphone switch without one and had constant buzz in audio from one of the rigs.  I added one transformer (on the audio from the left rig) to allow isolating the grounds between rigs and it silenced the buzz.  I used a 1:1 audio transfromer from local electronics store with no mfr. or part number markings.

------------ REPLY FOLLOWS ------------

This problem is invariably caused by a different ground potential
between the two units. An opto or isolation transformer will "fix" the
problem, but there is a better way: Eliminate the ground potential
difference in the first place. 

You need to do two things:

1. Use a heave ground wire to bond the two (or more) chassis together.
Keep the units close together so the ground wire is as short as
possible, ideally less than a foot or so.

2. Plug the AC cords of all power supplies, including the computer,
into one wall outlet, using a multiple jack extension as needed. Using
one outlet on one wall and another outlet on another wall is asking
for ground loop trouble if the outlets are on different circuits
within the house. You need a single point ground.

I've been doing it this way for years without an opto or isolation
transformer in the place. Works fine.

Bill, W6WRT