Re: LF: low pass filter for power use

[Rik Strobbe <rik.strobbe@fys.kuleuven.be>]

Hello Tom,

I believe the first one is the "G3YXM filter". 
The pitfalls when using a 147 kHz filter might be:
- higher attenuation at 137 kHz
- more sensitive to changes of the antenna impedance (if the antenna is
not 50 Ohm then it will affect the filter, largest changes are at
frequencies close to the "filter slope").

73, Rik  ON7YD

At 17:21 3/11/2005 +0100, you wrote:

> Hi
> Lf's
> in all circuit diagrams I find filters like
> 12nF---->54uH---->27nF----->54uH----->12nF
> here is the 3db point at 250khz.
> Has anyone test a filter in this configuration 47nF----->
> 54uH----->82nF------54uH----->47nF
> here is the 3db point at 147khz.
> The 2. filter gives a better suppress of the harmonics!
> Wat is the reason that all use the fist one?
>
> best 73' Tom DL4EAU


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