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From: "Clemens Paul" <cpaul@gmx.net>
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Precedence: bulk
Date: Fri, 30 Aug 2013 19:52:56 +0200
Subject: [rsgb_lf_group] RE: LF: iron powder toroid cores
Reply-To: rsgb_lf_group@yahoogroups.co.uk
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Hi Rik,=20

>So on 475 kHz the flux will be double compared to 1850 kHz.

Agreed.

>Or otherwise said: on 475 kHz you can only use half the power=20
>you can use on 1850 kHz.

I would expect half the voltage for the same flux which is one fourth of th=
e power.

But,according to the mini ringcore calculator
*given the same flux* temperature rise is MUCH less on 475kHz
than on 1900kHz ( 32=B0C vs 165=B0C !) which seems reasonable=20
because losses increase with frequency while flux decreases with frequency.

>But as the cores have rounded egdes there wil be some air space
> between the wire an the core, what might increase loss.

I can't see any reason why losses should increase due to some air gap.
Only the overall effective =B5_rel would slightly decrease and hence
the inductance.

73
Clemens
DL4RAJ=20

>-----Original Message-----
>From: owner-rsgb_lf_group@blacksheep.org=20
>[mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Rik Strobbe
>Sent: Friday, August 30, 2013 12:44 PM
>To: rsgb_lf_group@blacksheep.org
>Subject: RE: LF: iron powder toroid cores
>
>Hi Christian,
>
>according to the "mini ringcore calculator" (by DL5SWB) it is=20
>just on the edge (a flux of 223 G while 221 G is the max.=20
>flux). But as I have sufficient T200-2 cores I prefer to be on=20
>the safe side, also taking in mind that modes as QRRS120 and=20
>WSPR will require a 2 minute carrier.
>
>For an indentical LPF filter (coil reactance remains the same)=20
>the flux will drop with the square root of the frequency=20
>increase. So on 475 kHz the flux will be double compared to 1850 kHz.
>Or otherwise said: on 475 kHz you can only use half the power=20
>you can use on 1850 kHz.
>
>73, Rik  ON7YD - OR7T
>
>________________________________________
>


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=20=20=20=20=20=20
=20=20=20=20=20=20
      <p>Hi Rik, <br>
<br>
&gt;So on 475 kHz the flux will be double compared to 1850 kHz.<br>
<br>
Agreed.<br>
<br>
&gt;Or otherwise said: on 475 kHz you can only use half the power <br>
&gt;you can use on 1850 kHz.<br>
<br>
I would expect half the voltage for the same flux which is one fourth of th=
e power.<br>
<br>
But,according to the mini ringcore calculator<br>
*given the same flux* temperature rise is MUCH less on 475kHz<br>
than on 1900kHz ( 32=B0C vs 165=B0C !) which seems reasonable <br>
because losses increase with frequency while flux decreases with frequency.=
<br>
<br>
&gt;But as the cores have rounded egdes there wil be some air space<br>
&gt; between the wire an the core, what might increase loss.<br>
<br>
I can&#39;t see any reason why losses should increase due to some air gap.<=
br>
Only the overall effective =B5_rel would slightly decrease and hence<br>
the inductance.<br>
<br>
73<br>
Clemens<br>
DL4RAJ <br>
<br>
&gt;-----Original Message-----<br>
&gt;From: <a href=3D"mailto:owner-rsgb_lf_group%40blacksheep.org">owner-rsg=
b_lf_group@blacksheep.org</a> <br>
&gt;[mailto:<a href=3D"mailto:owner-rsgb_lf_group%40blacksheep.org">owner-r=
sgb_lf_group@blacksheep.org</a>] On Behalf Of Rik Strobbe<br>
&gt;Sent: Friday, August 30, 2013 12:44 PM<br>
&gt;To: <a href=3D"mailto:rsgb_lf_group%40blacksheep.org">rsgb_lf_group@bla=
cksheep.org</a><br>
&gt;Subject: RE: LF: iron powder toroid cores<br>
&gt;<br>
&gt;Hi Christian,<br>
&gt;<br>
&gt;according to the &quot;mini ringcore calculator&quot; (by DL5SWB) it is=
 <br>
&gt;just on the edge (a flux of 223 G while 221 G is the max. <br>
&gt;flux). But as I have sufficient T200-2 cores I prefer to be on <br>
&gt;the safe side, also taking in mind that modes as QRRS120 and <br>
&gt;WSPR will require a 2 minute carrier.<br>
&gt;<br>
&gt;For an indentical LPF filter (coil reactance remains the same) <br>
&gt;the flux will drop with the square root of the frequency <br>
&gt;increase. So on 475 kHz the flux will be double compared to 1850 kHz.<b=
r>
&gt;Or otherwise said: on 475 kHz you can only use half the power <br>
&gt;you can use on 1850 kHz.<br>
&gt;<br>
&gt;73, Rik  ON7YD - OR7T<br>
&gt;<br>
&gt;________________________________________<br>
&gt;<br>
<br>
</p>

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