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From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Thread-Topic: LF: iron powder toroid cores
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Date: Fri, 30 Aug 2013 10:44:26 +0000
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Subject: RE: LF: iron powder toroid cores
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Hi Christian,

according to the "mini ringcore calculator" (by DL5SWB) it is just on the e=
dge (a flux of 223 G while 221 G is the max. flux). But as I have sufficien=
t T200-2 cores I prefer to be on the safe side, also taking in mind that mo=
des as QRRS120 and WSPR will require a 2 minute carrier.

For an indentical LPF filter (coil reactance remains the same) the flux wil=
l drop with the square root of the frequency increase. So on 475 kHz the fl=
ux will be double compared to 1850 kHz.
Or otherwise said: on 475 kHz you can only use half the power you can use o=
n 1850 kHz.

73, Rik  ON7YD - OR7T

________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org=
] namens C. Groeger [aot.aot@gmx.de]
Verzonden: vrijdag 30 augustus 2013 12:09
To: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: iron powder toroid cores

Hi Rik,
One T200_2 is enough for that power. I tried it on 160m at 1000w.
Temperature was abaout 40C.

Hpe cu on 630
Df5qg

Christian Groeger

Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> schrieb:

>Dear all,
>
>
>
>I intend to replace the air coils in the LPF on my 475 kHz transmitter by =
toroid core coils. I have a stock of T200-2 cores but for the power level w=
ant to get (500W would be required to get near the 5 W EIRP limit)  one T20=
0-2 is just on the edge in regard with the maximum flux (and thus temperatu=
re rise.
>
>To be on the save side I would use 2 T200-2 toroids for each coil, and the=
re are 2 options:
>
>
>
>1. Glue 2 cores together to make one core of the double height.
>
>This would reduce the flux to 70%, well under the limit. It would also red=
uce the number of windings to 70%, but due to the double coil height the wi=
re length will increase slightly (abt. 10%).
>
>But as the cores have rounded egdes there wil be some air space between th=
e wire an the core, what might increase loss.
>
>
>
>2. Put 2 toroid core coils, each of half the inductance, in series.
>
>This will also reduce the flux to 70%, but the total wire length needed wi=
ll increase by abt. 40%.
>
>
>
>In option 1 I will need lees wire (=3D less loss) compared to option 1, bu=
t the air space might undo this advantage.
>
>
>
>So my question is: what will be best?
>
>All advice is welcome.
>
>
>
>73, Rik  ON7YD - OR7T
>
>=