Date: Tue, 29 Apr 2003 12:40:34 -0400
From: "Ralph Lane" <rlane7301@comcast.net>
To: rsgb_lf_group@blacksheep.org
Message-ID: <001901c30e6e$0e70a2c0$0000a398@yourw92p4bhlzg>
MIME-Version: 1.0
References: <5.1.0.14.0.20030429145925.00ae4c60@gemini.herts.ac.uk>
Subject: LF: Re: LF Tuning meter
Content-Type: text/plain; charset=iso-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Sender: <owner-rsgb_lf_group@blacksheep.org>
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org

I would like a copy of your low freq tuning meter.
Thanks,
Ralph
----- Original Message -----
From: "James Moritz" <j.r.moritz@herts.ac.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, April 29, 2003 10:36 AM
Subject: LF: LF Tuning meter


> 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!
>
> Cheers, Jim Moritz
> 73 de M0BMU
>
>
>