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@frontier.com>
>Sent: Mar 21, 2014 1:46 PM
>To: RFI <rfi@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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