[RFI] Ott filter

[Dale]

Ken,

Sadly, building EFFECTIVE filters is not an easy (nor inexpensive) task.  Commercially, there are high performance filters that start serious attenuation at either 10 kHz or 14 kHz, and then there are medium performance filters that start serious attenuation at either 100 kHz or 1 MHz.  NONE of these are in the price class of being under $100.  "Serious" attenuation means having at least 60 dB of insertion loss at the lowest specified frequency, and increasing in loss to a max of 80 to 120 dB, depending upon design and requirements.

Using your hefty hunk of iron and copper is not likely to work well.  For one thing, the inter-winding capacitance between primary and secondary provides a "sneak" path for RFI to couple around the device.  Another factor is that a successful power line filter employs both differential and common mode attenuation.  That means use of caps across the line hot and neutral, as well as caps between hot and ground and neutral and ground.  It is not uncommon for filters that provide significant attenuation at 10 kHz to have upwards of 3.5 AMPS of shunt current flowing in the caps that go from line to neutral and from line to ground.  It's all reactive current, but it is real current and runs up the power drain quickly.

73, Dale
WA9ENA          


-----Original Message-----
>From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
>Sent: Mar 21, 2014 1:46 PM
>To: RFI <rfi at contesting.com>
>Subject: [RFI] Ott filter
>
>OK. After some research, I find that the Ott filter was designed by one, Henry 
>Ott. It has some special characteristics which I, at least, would find extremely 
>valuable in the present situation.
>
>I own two very heavy 110 VAC to 110 VAC at 15 amps transformers here: I 
>wonder if I could use one of these in combination with some capacitors to 
>build a 60 Hz filter which would allow passage of 60 Hz while attenuating 
>everything else.
>
>Suggestions?
>
>Kenneth G. Gordon W7EKB
>
>"Courage is being scared to death but saddling up anyway."--- John   Wayne
>
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