AW: LF: low pass filter for power use

["Thomas Eckart" <dl4eau@t-online.de>]

Hi Rik,

thanks for info!

Yes, I use the type 2. filter and there are some problems. I think to change to the "normal" one.

But my filter still works, but sometimes it is a little rough to tune the amplifier.

thanks,

Tom

 

-----Ursprüngliche Nachricht-----
Von: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org]Im Auftrag von Rik Strobbe
Gesendet: Donnerstag, 3. November 2005 17:37
An: rsgb_lf_group@blacksheep.org
Betreff: Re: LF: low pass filter for power use

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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