[RFI] Magnetic Field Interference

[Brendan Minish]

Jim Brown wrote:
> On Sun, 14 Mar 2010 12:44:57 +0000, Brendan Minish wrote:
> 
>> The magnetic field has quite a high harmonic content
> 
> The magnetic field from a transformer is usually pure mains frequency.


I was looking directly at the magnetic field with a solenoid coil and a 
scope.

  If
> you're hearing harmonics especially odd order harmonics, it's likely that 
> you've somehow got some earth leakage currents in the mix. It's easy for that 
> to happen if there are unbalanced audio connections. 

there are no leakage currents at play here and relocating the amp has 
reduced the issue to an insignificant level but thanks for suggesting 
it, it is indeed a very common issue

73
Brendan EI6IZ