[Elecraft] Power Supply Ferrite Beads.

[G3VVT at aol.com]

In a message dated 16/05/05 23:08:10 GMT Daylight Time, n6wg at comcast.net  
writes:

First,  for the ac cord, use a large enough toroid so that you can get  a
number
of turns through it.  Try to get them to lay smoothly next  to each other,
rather than bunching and crossing over each other.  You  can remove the ac
plug for the winding, then install a new one when the  windings are done.



Reply: -------------------------------------------------------
 
Like Bob, N6WG I used a large ferrite ring that was sold at a hamfest for  
use to construct a filter for hi-fi interference and TVI  suppression at HF at 
about US$1.00 each. Through this wound as many turns of 3  conductor AC power 
cord that would fit laid flat with it's outer sheath removed.  Ended up with 
about 12 turns secured with plastic cable ties. In my case was  using this to 
suppress a noisy PC switched mode supply at HF so added an  IEC free socket on 
the end of the short cable tail. The  incoming power was taken through one of 
the shielded IEC chassis  mounting filter with male connector that are 
available in the market.  Mounted the whole lot in a plastic box with an added MOV 
suppresser to remove  spikes mounted at the terminals of the IEC filter. This is 
only added for the  benefit of the PC to prevent spikes causing system 
crashes. Mounted the box  next to the power socket on the PC switch mode PSU to keep 
any leads  short.
 
Works well allowing me to have the PC running at the same time as working  HF 
which was just about impossible before. Purposely suppressed all three  
conductors including ground which decoupled the PSU case and by default the PC  to 
contain the interference sources. Noted that a commercial power  filter for 
telephone switch use was found to be similar, with all three  conductors 
including the ground lead decoupled with an inductors.
 
Bob, G3VVT