Content-Transfer-Encoding: 8bit
Message-ID: <5.2.0.9.0.20030429145028.01d507b0@pop.1und1.com>
Date: Tue, 29 Apr 2003 14:51:20 +0100
To: rsgb_lf_group@blacksheep.org
From: "Fabian Kurz" <fk@diolog.de>
In-reply-to: <5.1.0.14.0.20030429145925.00ae4c60@gemini.herts.ac.uk>
MIME-Version: 1.0
Subject: Re: LF: LF Tuning meter
Content-Type: text/plain; charset=us-ascii; format=flowed
Sender: <owner-rsgb_lf_group@blacksheep.org>
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

At 15:36 29.04.2003 +0100, you wrote:
>Dear LF Group,
>
>For tuning LF antennas, I have for some time been using an oscilloscope to 
>monitor the current and voltage waveforms at the TX output. Resonance 
>occurs when V and I are in phase, and the load resistance is 50ohms when 
>V/I = 50. This is very easy to use provided a scope is to hand, but not 
>very useful if it isn't. An SWR bridge can be used, but it only indicates 
>the degree of mismatch, so tuning is still a matter of trial and error. So 
>with a mind towards future /P operations, I have built a self-contained 
>tuning meter.
>
>The prototype has 2 meters - one indicates phase, while the other can be 
>switched between voltage and current to determine the load resistance. The 
>circuit is slightly more complex than an SWR bridge, but not by very much 
>- it uses 12 diodes, 3 toroid cores and a few other passive components. It 
>does not require an external power supply, and is usable with TX power 
>between about 20W and 1.8kW. I have written a 3 page article about it - it 
>is a pdf file of about 190k, so too big for the reflector, but I can 
>e-mail it as an attachment to those who are interested. If someone would 
>like to put it on their web site, they would be more than welcome!


I'd appreciate a copy of the pdf-File!

73, Fabian DJ1YFK (currently upgrading the PA some 10dB, so a normal CW QSO 
is certainly possible soon ;)


>Cheers, Jim Moritz
>73 de M0BMU
>