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Original Message -----
Sent:
Friday, June 29, 2012 9:26 PM
Subject:
LF: Fwd: Help needed, mechanical filters
4th try...
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MF,
I have bought a mechanical filter which has a center frequency of 473
kHz. It is available at
http://www.oppermann-electronic.de/html/body_hf-spezialbauteile.html
(scroll down to FZ 01 / FZ 02). I have both types and just measured the
frequency response. There is a data sheet as well which states the
impedances to be connected to the wires.
There is even a datasheet at
http://www.oppermann-electronic.de/assets/applets/FZ_01.pdf
All in all it looks very interesting and the slopes are really very
sharp. However there is a passband ripple of 10 dB which is very very
high. See the image:
https://dl.dropbox.com/u/19882028/MF/Mechanisches%20Filter%20473%20kHz.png
So what have i done wrong? Or is it that bad?
The input signal is connected on the left side between the red and green
wire. The output signal is taken from the right side on the red and
green wire too. It looks as if each side has a coil on the green and red
wire, with a tap at the yellow wire.
Helpful was this image from the web
http://www.amateurfunkmuseum.de/AFM_321b-Dateien/image006.jpg which
shows a similar filter. I have connected a resistor of 18 kOhm to the
output and a 500 Ohm resistor in series to the signal generator, as
stated in the datasheet. But the ripple does not change.
Any ideas or suggestions?
Guess for what i will need the filter! :-)
73, Stefan/DK7FC
