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Date: Sat, 05 Mar 2011 16:48:30 +0000
From: "qrss@talktalk.net" <qrss@talktalk.net>
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References: <AANLkTimy87NkJ3VXf4qeQ3NMehA_6HzAe6mHBJ6M_Sts@mail.gmail.com>	<4D72471D.30904@talktalk.net> <AANLkTincU_L7bHAKNmqLWuOmmMv114MY0=FAjKCyP=0m@mail.gmail.com>
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Subject: Re: LF: Sub 9kHz antenna tests.
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Hi Gary

Thanks for the reply, first thing, for "10dB hump at 8.9kHz" read 20dB. 
Direct coupling of coax to the feed was killing the Q, I have added a 4 
turn coupling loop. The flatness was only really noted once it was outside.

I can see the need for an amplifier on a broad band loop as with the 
E-Probe which is non resonant and at a few inches long hasn't got a lot 
going for it but not for a resonant loop which untuned produces 10dB of 
noise and resonant 30dB I am dubious still.

Maybe M0BMU will have a comment :-) please.

73 Eddie G3ZJO


On 05/03/2011 15:21, Gary - G4WGT wrote:
> Hi Eddie,
>
> Yes, you will need a pre-amp, don' forget that the E-Probe has a 
> pre-amp. I advise you to build the M0BMU VLF pre-amp with 7 to 10 kHz 
> band-pass filter, circuit attached.
>
> 73, Gary - G4WGT.
>
>
> On 5 March 2011 14:22, qrss@talktalk.net <mailto:qrss@talktalk.net> 
> <qrss@talktalk.net <mailto:qrss@talktalk.net>> wrote:
>
>     Hi Gary
>
>     I am testing a very similar loop to your 1.1m square, mine is
>     800mm sq. and uses Litz wire. Results at the same hight as my
>     E-Probe are disappointing as yet.
>
>     I have no pre amp on it, and am wondering whether it would be
>     advantageous as when tuned to 8.9kHz the noise level rises by
>     10dB. I suppose I shall end up building an amp to try but I would
>     welcome any thoughts from the group.
>
>     73 Eddie G3ZJO
>
>
>     On 05/03/2011 12:35, Gary - G4WGT wrote:
>
>         Hi All,
>
>         Whilst monitoring 9090kHz & 8970kHz using SpecLab at 423uHz, I
>         am testing 3 different VLF Rx antenna types :-
>
>         1 - An 84mH shielded ferrite loopstick (10mm x 200mm), 1 metre
>         above ground
>         2 - A modified PA0RDT Mini-Whip, 8 metres above ground
>         3 - A 1.1 metre square loop with 46 turns of 1mm insulated
>         wire, 1 metre above ground
>
>         Both of the loops using M0BMU VLF pre-amp.
>
>         I have had No. 1 connected since 2000utc last night until
>         1030utc this morning, no signals detected on the SpecLab
>         display. I have connected No. 2 at 1030utc & notice a fall in
>         noise level of about 10dB & a greater visibility of the Alpha
>         signals. Later today I will connect the large loop & report my
>         findings.
>
>         73,
>
>         Gary - G4WGT - IO83qo.
>
>
>
>


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    Hi Gary<br>
    <br>
    Thanks for the reply, first thing, for "10dB hump at 8.9kHz" read
    20dB. Direct coupling of coax to the feed was killing the Q, I have
    added a 4 turn coupling loop. The flatness was only really noted
    once it was outside.<br>
    <br>
    I can see the need for an amplifier on a broad band loop as with the
    E-Probe which is non resonant and at a few inches long hasn't got a
    lot going for it but not for a resonant loop which untuned produces
    10dB of noise and resonant 30dB I am dubious still.<br>
    <br>
    Maybe M0BMU will have a comment :-) please.<br>
    <br>
    73 Eddie G3ZJO<br>
    <br>
    <br>
    On 05/03/2011 15:21, Gary - G4WGT wrote:
    <blockquote        cite="mid:AANLkTincU_L7bHAKNmqLWuOmmMv114MY0=FAjKCyP=0m@mail.gmail.com"        type="cite">Hi Eddie,
      <div><br>
      </div>
      <div>Yes, you will need a pre-amp, don' forget that the E-Probe
        has a pre-amp. I advise you to build the M0BMU VLF pre-amp with
        7 to 10 kHz band-pass filter, circuit attached.</div>
      <div><br>
      </div>
      <div>73, Gary - G4WGT.</div>
      <div><br>
        <br>
        <div class="gmail_quote">On 5 March 2011 14:22, <a              moz-do-not-send="true" href="mailto:qrss@talktalk.net">qrss@talktalk.net</a>
          <span dir="ltr">&lt;<a moz-do-not-send="true"                href="mailto:qrss@talktalk.net">qrss@talktalk.net</a>&gt;</span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt              0.8ex; border-left: 1px solid rgb(204, 204, 204);              padding-left: 1ex;">Hi Gary<br>
            <br>
            I am testing a very similar loop to your 1.1m square, mine
            is 800mm sq. and uses Litz wire. Results at the same hight
            as my E-Probe are disappointing as yet.<br>
            <br>
            I have no pre amp on it, and am wondering whether it would
            be advantageous as when tuned to 8.9kHz the noise level
            rises by 10dB. I suppose I shall end up building an amp to
            try but I would welcome any thoughts from the group.<br>
            <br>
            73 Eddie G3ZJO
            <div>
              <div class="h5"><br>
                <br>
                On 05/03/2011 12:35, Gary - G4WGT wrote:<br>
                <blockquote class="gmail_quote" style="margin: 0pt 0pt                    0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204);                    padding-left: 1ex;">
                  Hi All,<br>
                  <br>
                  Whilst monitoring 9090kHz &amp; 8970kHz using SpecLab
                  at 423uHz, I am testing 3 different VLF Rx antenna
                  types :-<br>
                  <br>
                  1 - An 84mH shielded ferrite loopstick (10mm x 200mm),
                  1 metre above ground<br>
                  2 - A modified PA0RDT Mini-Whip, 8 metres above ground<br>
                  3 - A 1.1 metre square loop with 46 turns of 1mm
                  insulated wire, 1 metre above ground<br>
                  <br>
                  Both of the loops using M0BMU VLF pre-amp.<br>
                  <br>
                  I have had No. 1 connected since 2000utc last night
                  until 1030utc this morning, no signals detected on the
                  SpecLab display. I have connected No. 2 at 1030utc
                  &amp; notice a fall in noise level of about 10dB &amp;
                  a greater visibility of the Alpha signals. Later today
                  I will connect the large loop &amp; report my
                  findings.<br>
                  <br>
                  73,<br>
                  <br>
                  Gary - G4WGT - IO83qo.<br>
                </blockquote>
                <br>
                <br>
              </div>
            </div>
          </blockquote>
        </div>
        <br>
      </div>
    </blockquote>
    <br>
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