Message-ID: <4F298512.1010305@usa.net>
Date: Wed, 01 Feb 2012 19:31:46 +0100
From: Alberto di Bene <dibene@usa.net>
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To: rsgb_lf_group@blacksheep.org
References: <4F286089.000027.05504@BOB-PC> <EE4DAAED21874BA5957F1FCB7C61722D@JimPC>
In-Reply-To: <EE4DAAED21874BA5957F1FCB7C61722D@JimPC>
Z-USANET-MsgId: XID340qBasfx6368X38
Subject: Re: LF: Re: Converting antenna
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On 2/1/2012 12:35 AM, James Moritz wrote:
> I guess as far as LF frequencies are concerned, the Butternut antenna is 
> just a 10m vertical whip (provided you disconnect the coil across the feed 
> point - otherwise it will be nearly a short circuited whip...). This will 
> give you plenty of signal, provided the antenna is reasonably matched to the 
> RX input. Matching requires tuning it to resonance. The simplest form of 
> tuner is just an inductor connected between the feed point of the antenna 
> and the low impedance RX input
Jim and the group,

  I used with good results the following schematic to match a random piece of wire
to an LF Rx.  Below also the Spice simulation. Gain is high, and is given only by the
passive impedance step-up, so there are no risks of distortion, as long as the Rx
does not saturate...

C1 is absolutely not critical, can range from 1nF to 4.7nF with no practical changes
in the performance of the circuit.

73  Alberto  I2PHD

http://dl.dropbox.com/u/15089947/LFmatchSch.gif

http://dl.dropbox.com/u/15089947/LFmatchGain.gif



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    On 2/1/2012 12:35 AM, James Moritz wrote:
    <blockquote cite=3D"mid:EE4DAAED21874BA5957F1FCB7C61722D@JimPC"
      type=3D"cite">
      <pre wrap=3D"">I guess as far as LF frequencies are concerned, the =
Butternut antenna is=20
just a 10m vertical whip (provided you disconnect the coil across the fee=
d=20
point - otherwise it will be nearly a short circuited whip...). This will=
=20
give you plenty of signal, provided the antenna is reasonably matched to =
the=20
RX input. Matching requires tuning it to resonance. The simplest form of=20
tuner is just an inductor connected between the feed point of the antenna=
=20
and the low impedance RX input</pre>
    </blockquote>
    <font face=3D"Tahoma">Jim and the group,<br>
      <br>
      =A0 I used with good results the following schematic to match a
      random piece of wire<br>
      to an LF Rx.=A0 Below also the Spice simulation. Gain is high, and
      is given only by the<br>
      passive impedance step-up, so there are no risks of distortion, as
      long as the Rx<br>
      does not saturate...<br>
      <br>
      C1 is absolutely not critical, can range from 1nF to 4.7nF with no
      practical changes<br>
      in the performance of the circuit.<br>
      <br>
      73=A0 Alberto=A0 I2PHD<br>
      <br>
      <img alt=3D"http://dl.dropbox.com/u/15089947/LFmatchSch.gif"
        src=3D"http://dl.dropbox.com/u/15089947/LFmatchSch.gif"
        moz-do-not-send=3D"true" height=3D"400" width=3D"738"><br>
      <br>
      <img alt=3D"http://dl.dropbox.com/u/15089947/LFmatchGain.gif"
        src=3D"http://dl.dropbox.com/u/15089947/LFmatchGain.gif"
        moz-do-not-send=3D"true" height=3D"609" width=3D"821"><br>
      <br>
      <br>
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