[sdiy] EM radiation -- current or power ?

[Andre Majorel]

On 2010-12-18 17:47 +0100, Magnus Danielson wrote:

> So, from an EMC perspective, reduce the loop area of those cables to
> reduce the H-field emission and shield it to reduce the E-field
> emission... and likewise for the receiving end. Lowering or Raisign
> the receving impedance can help in separation of mainly E-field or
> H-field sensitivity of the receiver. Lower impedance reduces E-field
> sensitivity, higher impedance reduces the H-field sensitivity. Since
> this is a reciprocal aspect, the same will be true for the
> transmission side. Matching the impedance to that of air helps to
> improve transmission.

Thanks for the replies everyone, that was instructive. It seems
that the answer is that it'll induce less hum into guitar
pickups but more into line level cables. And using twisted pair
shielded cable for power would help (twisted for line, shielded
for guitar pickups).

The same cable will carry two 18 V secondaries but they'll
obviously be in phase and I don't know how much cancellation
will occur. A new application for star quad ?

Leaving the rectifier bridge and smoothing caps close to the
voltage regulator is attractive because AC is easier on the
switches. I also have a vague notion that AC is more flexible
than DC but I'm not sure exactly how.

-- 
André Majorel http://www.teaser.fr/~amajorel/