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Re: LF: Low pass filter 1 kW 136k 472 k what components to choose?

To: [email protected]
Subject: Re: LF: Low pass filter 1 kW 136k 472 k what components to choose?
From: John Andrews <[email protected]>
Date: Sun, 21 Dec 2014 11:01:00 -0500
In-reply-to: <[email protected]-webde-bs34>
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W1VD and I use the "half-wave" filters described at:

Jay's method of construction probably has a better HF/VHF stop-band, but I have gotten away with a single chassis for all components.
In terms of practical harmonic suppression, the 2nd and 3rd harmonics
offer no interference to weak AM broadcast signals on our street about
100 meters from the antenna while operating in the 472 kHz band. There
are definite AM interference problems at my house, however. I have done
no other measurements.
John, W1TAG

On 12/21/2014 10:38 AM, Hans-Albrecht Haffa wrote:
Dear OMs,
just a question strait forward: What componnets I should choose for a
low pass filter for 136 kHz and 472 kHz, two filters to be designed.
*136 kHz:  Pin abt 1,5 kW*
*472 kHz:  Pin abt 0,5 kW*
SWR: s = 1...2,5 when mated, in case of failure more
a five-pole low pass will probably be sufficient.
My Question:
What iron powder cores or air coiles will do it, known or proofed by
experiment? Diameter, marterial grade?
What capacitors? max. Voltage.  High voltage caps from Wima (Ucd=4kV or
8 kV) are not available at distributors, mica capacitors will hardly fit
in capacitiy value or in voltage, when in my collection.
The calculus of magnetic circuits is not a problem for me, but it is
easier to start with components that will fulfill the demands.
Waiting to Your kind anwer,
55, Hans-Albrecht

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