[Elecraft] Switching Power Supplies-RF Filtering

[n4so@juno.com]

Ideas for RFI filtering are from a QST article on building a Switching
Power Supply.  The basic principles of RF filtering would apply to any
switching power supply.

1.  Line voltage is EMI filtered and an additional noise filter for
common-mode currents is used, following the first EMI filter.
2.  The 13.8 V dc cables use  Amidon FB-73-2401 ferrite beads, 
with six on each cable for a total of twelve beads.  The output power
cable filtering is completed by six bypass capacitors on the output
leads.  The ground is floating to reduce stray HF currents.
3.  L3 is a noise absorber using a ferrite solenoid.
4.  Between C3 and the power oscillator, Type-73 beads are used to
absorb noise.   L2 is a toroid choke, and absorbs most of the noise on
the
output side.

Manfred Mornhinweg, XQ2FOD, A 13.8-V, 40-A Switching Power
Supply,  QST, December, 1998,  p. 37-41.


Ken Brown-N4SO
Mobile, AL  EM50tk
Elecraft K-1
4 ele. monoband yagi
N4SO@juno.com


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