[Boatanchors] Speech Amp Again

[Mike Andrews W5EGO]

On Wed, Nov 19, 2008 at 02:53:04PM -0500, Carl wrote:
> Shielding may create a ground loop problem between units. If hum is a 
> problem try the shielding with grounding at one end at a time and then 
> both. As John said twisting is the most important step, as it cancels 
> common mode problems.
> 
> Im using twisted # 16 cloth covered wire (just like in the old days) to 
> both of my modulator decks with no hum pickup.

Another dodge I've seen used in cases where fields were strong enough 
to cause RF pickup problems, but where connecting the shield at both 
ends caused ground loop problems, was to use double-shielded cable, 
with the inner shield connected at one end and the outer shield at 
the other. 

This probably is overkill for your situation, but has worked as a last-
ditch remedy in a few places. I expect that twisted pair wiring will 
suffice in 90% or more of the cases. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin