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From: =?iso-8859-1?Q?Petr_Mal=FD?= <p.maly@gmc.net>
To: <rsgb_lf_group@blacksheep.org>
Date: Thu, 2 Apr 2009 09:26:22 +0200
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Subject: LF: Tune and match the ant for 50kHz...550kHz
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Hi all,

I want to make a small transmatch (RX, TX up to 10 Watts, or so) to tune LW=20=
41 m (or smaller T-ant) in the range 50 ... 550 kHz.
I am not too good in theory... but I believe that the most efficient system=20=
is the popular loading coil (home made variometer, and taps to find 50 Ohms=20=
match).
The simple variometer (cylindrical coil in another cylindrical coil) is easy=
 to make and works fine on 136kHz. However, it is possible to change inducta=
nce in the range about 1:2 or 1:3 only, not much better. Therefore the redud=
ant inductance is too high to fetch the ant to resonance on 550 kHz.
Solution would be to make a more sophisticated variometer (best: sphere in s=
phere) to reach the ratio 1:10 or so.
Or, to use a different kind of network. Pi network, L network or T network.=20=
BTW I would also prefer to use a rotary switch and solder twenty condensers=20=
rather than to make twenty taps on a coil wound with litz wire...

How did you solve this yourself?

Thanks, 73, Petr, OK1FIG


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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; charset=3Diso-8859-1">
<META content=3D"MSHTML 6.00.6001.18203" name=3DGENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Hi all,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>I want to make a small transmatch (RX, TX u=
p to 10=20
Watts, or so) to tune LW 41 m (or smaller T-ant) in the range 50 ... 550=20
kHz.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>I am not too good in theory... but I believ=
e that=20
the most efficient system is the&nbsp;popular&nbsp;loading coil (home made=20
variometer, and taps to find 50 Ohms match).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>The simple variometer (cylindrical coil in=20=
another=20
cylindrical coil) is easy to make and works fine on 136kHz. However, it is=20
possible to change inductance in the range about 1:2 or 1:3 only, not much=20
better. Therefore the redudant inductance is too high to fetch the ant to=20
resonance on 550 kHz.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Solution would be to make a more sophistica=
ted=20
variometer (best: sphere in sphere) to reach the ratio 1:10 or so.</FONT></D=
IV>
<DIV><FONT face=3DArial size=3D2>Or, to use a different kind of network. Pi=20=
network,=20
L network or T network. BTW I would also prefer to use a rotary switch and=20
solder&nbsp;twenty condensers rather than to make twenty taps on a&nbsp;coil=
=20
wound with litz wire...</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>How did you solve this yourself?</FONT></DI=
V>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Thanks, 73, Petr, OK1FIG</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV></BODY></HTML>

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