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Message-ID: <0F87F4C0AE524B1E9EA631C81D579573@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <4FEE0F7E.2090109@iup.uni-heidelberg.de>
Date: Fri, 29 Jun 2012 23:08:08 +0100
MIME-Version: 1.0
Subject: LF: Re: Fwd: Help needed, mechanical filters
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Stefan if they are really that old then they mar be deterioration of the =
elements. I remember the Kokusai fikters used in KW TX and RX designs =
(much bigger profile) degraded over the years. I have a few of those =
type of filters, my measurements suggest that ripple was not an =
important aspect (perticularly if they were for NBFM. However they look =
more like AM filters .....Mikes idea is good I found that the best shape =
is not always with the specified termination. PMR makers are more =
interested in adjacent channel suppression than in-band linearity. A =
lower termination impedance will flatten the response but also reduce =
the out-of-band attenuation, and probably the slope, and increase the =
insertion loss. They can be cascaded .....gain is cheap at those =
frequencies.

Alan G3NYK

  ----- Original Message -----=20
  From: Stefan Sch=E4fer=20
  To: rsgb_lf_group@blacksheep.org=20
  Sent: Friday, June 29, 2012 9:26 PM
  Subject: LF: Fwd: Help needed, mechanical filters


  4th try...=20

  -------- Original-Nachricht -------- Betreff:  Help needed, mechanical =
filters=20
        Datum:  Fri, 29 Jun 2012 20:58:41 +0200=20
        Von:  Stefan Sch=E4fer <schaefer@iup.uni-heidelberg.de>=20
        An:  rsgb_lf_group@blacksheep.org=20



MF,

I have bought a mechanical filter which has a center frequency of 473=20
kHz. It is available at=20
http://www.oppermann-electronic.de/html/body_hf-spezialbauteile.html=20
(scroll down to FZ 01 / FZ 02). I have both types and just measured the=20
frequency response. There is a data sheet as well which states the=20
impedances to be connected to the wires.
There is even a datasheet at=20
http://www.oppermann-electronic.de/assets/applets/FZ_01.pdf

All in all it looks very interesting and the slopes are really very=20
sharp. However there is a passband ripple of 10 dB which is very very=20
high. See the image:=20
https://dl.dropbox.com/u/19882028/MF/Mechanisches%20Filter%20473%20kHz.pn=
g

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=20
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=20
http://www.amateurfunkmuseum.de/AFM_321b-Dateien/image006.jpg which=20
shows a similar filter. I have connected a resistor of 18 kOhm to the=20
output and a 500 Ohm resistor in series to the signal generator, as=20
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

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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content=3D"text/html; charset=3DISO-8859-15" =
http-equiv=3Dcontent-type>
<META name=3DGENERATOR content=3D"MSHTML 8.00.6001.19258">
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff text=3D#000000>
<DIV><FONT size=3D2 face=3DArial>Stefan if they are really that old then =
they mar be=20
deterioration of the elements. I remember the Kokusai fikters used in KW =
TX and=20
RX designs (much bigger profile) degraded over the years. I have a few =
of those=20
type of filters, my measurements suggest that ripple was not an =
important aspect=20
(perticularly if they were for NBFM. However they look more like AM =
filters=20
.....Mikes idea is good I found that the best shape is not always with =
the=20
specified termination. PMR makers are more interested in adjacent =
channel=20
suppression than in-band linearity. A lower termination impedance will =
flatten=20
the response but also reduce the out-of-band attenuation, and probably =
the=20
slope, and increase the insertion loss. They can be cascaded .....gain =
is cheap=20
at those frequencies.</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>Alan G3NYK</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"=20
dir=3Dltr>
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: =
black"><B>From:</B>=20
  <A title=3DStefan.Schaefer@iup.uni-heidelberg.de=20
  href=3D"mailto:Stefan.Schaefer@iup.uni-heidelberg.de">Stefan =
Sch=E4fer</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Drsgb_lf_group@blacksheep.org=20
  =
href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org=
</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Friday, June 29, 2012 =
9:26 PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> LF: Fwd: Help needed, =
mechanical=20
  filters</DIV>
  <DIV><BR></DIV>4th try... <BR><BR>-------- Original-Nachricht -------- =

  <TABLE class=3Dmoz-email-headers-table border=3D0 cellSpacing=3D0 =
cellPadding=3D0>
    <TBODY>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>Betreff: </TH>
      <TD>Help needed, mechanical filters</TD></TR>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>Datum: </TH>
      <TD>Fri, 29 Jun 2012 20:58:41 +0200</TD></TR>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>Von: </TH>
      <TD>Stefan Sch=E4fer <A class=3Dmoz-txt-link-rfc2396E=20
        =
href=3D"mailto:schaefer@iup.uni-heidelberg.de>">&lt;schaefer@iup.uni-heid=
elberg.de&gt;</A></TD></TR>
    <TR>
      <TH vAlign=3Dbaseline noWrap align=3Dright>An: </TH>
      <TD><A class=3Dmoz-txt-link-abbreviated=20
        =
href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org=
</A></TD></TR></TBODY></TABLE><BR><BR><PRE>MF,

I have bought a mechanical filter which has a center frequency of 473=20
kHz. It is available at=20
<A class=3Dmoz-txt-link-freetext =
href=3D"http://www.oppermann-electronic.de/html/body_hf-spezialbauteile.h=
tml">http://www.oppermann-electronic.de/html/body_hf-spezialbauteile.html=
</A>=20
(scroll down to FZ 01 / FZ 02). I have both types and just measured the=20
frequency response. There is a data sheet as well which states the=20
impedances to be connected to the wires.
There is even a datasheet at=20
<A class=3Dmoz-txt-link-freetext =
href=3D"http://www.oppermann-electronic.de/assets/applets/FZ_01.pdf">http=
://www.oppermann-electronic.de/assets/applets/FZ_01.pdf</A>

All in all it looks very interesting and the slopes are really very=20
sharp. However there is a passband ripple of 10 dB which is very very=20
high. See the image:=20
<A class=3Dmoz-txt-link-freetext =
href=3D"https://dl.dropbox.com/u/19882028/MF/Mechanisches%20Filter%20473%=
20kHz.png">https://dl.dropbox.com/u/19882028/MF/Mechanisches%20Filter%204=
73%20kHz.png</A>

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=20
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=20
<A class=3Dmoz-txt-link-freetext =
href=3D"http://www.amateurfunkmuseum.de/AFM_321b-Dateien/image006.jpg">ht=
tp://www.amateurfunkmuseum.de/AFM_321b-Dateien/image006.jpg</A> which=20
shows a similar filter. I have connected a resistor of 18 kOhm to the=20
output and a 500 Ohm resistor in series to the signal generator, as=20
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
</PRE></BLOCKQUOTE></BODY></HTML>

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