From: DK1IS <DK1IS@kabelmail.de>
To: rsgb_lf_group@blacksheep.org, rsgb-lf-group@groups.io
References: <5CADE53C.30201@posteo.de>
 <e0ba3e0c-ea1e-4858-1291-c88dbd0d69f4@aeritel.com>
Message-ID: <b94b2f43-2d07-1128-3066-3be4c72cbf62@kabelmail.de>
Date: Thu, 18 Apr 2019 19:31:13 +0200
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Subject: Re: LF: NEW VLF antenna
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Am 18.04.2019 um 16:11 schrieb info@aeritel.com:
>
> Hallo,
>
> https://incompliancemag.com/creating-a-novel-compact-antenna-that-can-g=
o-where-radios-cant/
>
> Friends are there any news? Home made new antenna??
>
>
> '73 from Richard - IK7FMO
>
>
Hi group,

a little bit OT, but the public interest seems to rise ;-)! At April 15,=20
Roman, RW3ADB, pointed out here a similar article leading to a more=20
detailled link:

https://www.nature.com/articles/s41467-019-09680-2.

The paper describes a kind of matching a low source impedance to a very=20
high load impedance by using a piezoelectric resonator. Thus it is=20
possible to feed an extremely short antenna with a very high voltage in=20
resonance without using lossy L-C-circuits, resulting in a relatively=20
"high" antenna current. Of course such a system has a very small=20
bandwidth and is frequency-wise very sensitive to stray capacitances at=20
the high-impedance side. The authors turn this to an advantage with=20
regard to a fast capacitve re-tuning when using it in DAM systems=20
(Direct Antenna Modulation). A second problem is that the crystal has to=20
stand voltages in the 100 kV range which is impossible for commercially=20
available quartz resonators. Therefore the authors use a special lithium=20
niobat crystal at about 35 kHz with 94 mm length which is mounted in a=20
chamber filled with hexafluoroethane gas - not so easy for a normal ham .=
...

Anyway, the idea is fascinating. Having no VLF crystals up to now, I=20
made some preliminary tests with a randomly available HC-6-U quartz, QRG=20
2434 kHz, wavelength 123 m. And yes, it works!

  * TX: Sythesizer Schomandl MG100M, 300 Hz ... 100 MHz, smallest step
    0.1 Hz, Ri =3D 50 Ohms, P =3D 10 dBm, output tied to first leg of
    quartz, alternatively direct to the antenna wire
  * RX: Perseus SDR with an active rod antenna on my garage, fed by a
    solar system, no external wire connections, air-line distance 100 m
    to my shack
  * Antena wire: 2 m or 4 m, laid out in the shack, tied to second leg
    of quartz, alternatively direct to the TX output

Results with 2 m antenna wire:

  * with quartz resonator: fres =3D 2,433,908.8 Hz, RX level at resonance
    =3D - 63,1 dBm, - 3dB-bandwidth =3D 48.3 Hz resulting in Q =3D 50391
  * without quartz resonator: RX level =3D - 85,4 dBm resulting in a gain
    of 22.3 dB with quartz
  * comparision: my 13 m T-Marconi with top load 4 x 33 m, tuned to 2434
    kHz and fed by the synthesizer with 10 dBm results in a RX level of
    - 32.1 dBm ;-)

Results with 4 m antenna wire:

  * with Quartz resonator: fres =3D 2,433,773.6 Hz, RX level at resonance
    =3D - 59 dBm. - 3 dB-bandwidth =3D 49.4 Hz resulting in Q =3D 49376
  * without quartz resonator: RX level =3D - 75.4 dBm resulting in a gain
    of 16.4 dB with quartz

So it seems the best effects can really be achieved with very short=20
antenna wires. The long range performance is in no way comparable with=20
more fullsized antennas but for special applicatios the features could=20
be interesting. For instance realising some capacitive feedback from the=20
vicinity of the antenna rod could result in a small low power beacon=20
with integrated matching - it even could be used as a presence detector=20
with direkt frequency read out ...

- But yes, Rik, I`ll certainly will keep my Marconi - making QSOs on VLF=20
costs enough efforts even when using a big antenna. But I=C2=B4ve alredy=20
orderd some VLF crystals on the bay ...

73 es Happy Easter!

Tom, DK1IS


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<html>
  <head>
    <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3DUTF=
-8">
  </head>
  <body text=3D"#000000" bgcolor=3D"#FFFFFF">
    <div class=3D"moz-cite-prefix">Am 18.04.2019 um 16:11 schrieb <a
        class=3D"moz-txt-link-abbreviated" href=3D"mailto:info@aeritel.co=
m">info@aeritel.com</a>:<br>
    </div>
    <blockquote type=3D"cite"
      cite=3D"mid:e0ba3e0c-ea1e-4858-1291-c88dbd0d69f4@aeritel.com">
      <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3DU=
TF-8">
      <p>Hallo,<br>
      </p>
      <p><font size=3D"1"><font face=3D"Verdana"><a
              class=3D"moz-txt-link-freetext"
href=3D"https://incompliancemag.com/creating-a-novel-compact-antenna-that=
-can-go-where-radios-cant/"
              moz-do-not-send=3D"true">https://incompliancemag.com/creati=
ng-a-novel-compact-antenna-that-can-go-where-radios-cant/</a></font></fon=
t></p>
      <p><font size=3D"1"><font face=3D"Verdana"><span
              class=3D"tlid-translation translation" lang=3D"en"><span
                title=3D"" class=3D"">Friends are there any news? Home ma=
de
                new antenna??</span></span></font></font></p>
      <p><font size=3D"1"><font face=3D"Verdana"><span
              class=3D"tlid-translation translation" lang=3D"en"><span
                title=3D"" class=3D""><br>
              </span></span></font></font></p>
      <p><font size=3D"1"><font face=3D"Verdana"><span
              class=3D"tlid-translation translation" lang=3D"en"><span
                title=3D"" class=3D"">'73 from Richard - IK7FMO<br>
              </span></span></font></font></p>
      <p><font size=3D"1"><font face=3D"Verdana"><br>
          </font></font></p>
    </blockquote>
    Hi group,<br>
    <p> a little bit OT, but the public interest seems to rise ;-)! At
      April 15, Roman, RW3ADB, pointed out here a similar article
      leading to a more detailled link: <a
        class=3D"moz-txt-link-freetext"
        href=3D"https://www.nature.com/articles/s41467-019-09680-2"><br>
        <br>
        https://www.nature.com/articles/s41467-019-09680-2</a>. <br>
      <br>
      The paper describes a kind of matching a low source impedance to a
      very high load impedance by using a piezoelectric resonator. Thus
      it is possible to feed an extremely short antenna with a very high
      voltage in resonance without using lossy L-C-circuits, resulting
      in a relatively "high" antenna current. Of course such a system
      has a very small bandwidth and is frequency-wise very sensitive to
      stray capacitances at the high-impedance side. The authors turn
      this to an advantage with regard to a fast capacitve re-tuning
      when using it in DAM systems (Direct Antenna Modulation). A second
      problem is that the crystal has to stand voltages in the 100 kV
      range which is impossible for commercially available quartz
      resonators. Therefore the authors use a special lithium niobat
      crystal at about 35 kHz with 94 mm length which is mounted in a
      chamber filled with hexafluoroethane gas - not so easy for a
      normal ham ...<br>
    </p>
    <p>Anyway, the idea is fascinating. Having no VLF crystals up to
      now, I made some preliminary tests with a randomly available
      HC-6-U quartz, QRG 2434 kHz, wavelength 123 m. And yes, it works!<b=
r>
    </p>
    <ul>
      <li>TX: Sythesizer Schomandl MG100M, 300 Hz ... 100 MHz, smallest
        step 0.1 Hz, Ri =3D 50 Ohms, P =3D 10 dBm, output tied to first l=
eg
        of quartz, alternatively direct to the antenna wire<br>
      </li>
      <li>RX: Perseus SDR with an active rod antenna on my garage, fed
        by a solar system, no external wire connections, air-line
        distance 100 m to my shack</li>
      <li>Antena wire: 2 m or 4 m, laid out in the shack, tied to second
        leg of quartz, alternatively direct to the TX output <br>
      </li>
    </ul>
    <p>Results with 2 m antenna wire:</p>
    <ul>
      <li>with quartz resonator: fres =3D 2,433,908.8 Hz, RX level at
        resonance =3D - 63,1 dBm, - 3dB-bandwidth =3D 48.3 Hz resulting i=
n Q
        =3D 50391</li>
      <li>without quartz resonator: RX level =3D - 85,4 dBm resulting in =
a
        gain of 22.3 dB with quartz</li>
      <li>comparision: my 13 m T-Marconi with top load 4 x 33 m, tuned
        to 2434 kHz and fed by the synthesizer with 10 dBm results in a
        RX level of - 32.1 dBm ;-)</li>
    </ul>
    <p>Results with 4 m antenna wire:</p>
    <ul>
      <li>with Quartz resonator: fres =3D 2,433,773.6 Hz, RX level at
        resonance =3D - 59 dBm. - 3 dB-bandwidth =3D 49.4 Hz resulting in=
 Q
        =3D 49376</li>
      <li>without quartz resonator: RX level =3D - 75.4 dBm resulting in =
a
        gain of 16.4 dB with quartz</li>
    </ul>
    <p>So it seems the best effects can really be achieved with very
      short antenna wires. The long range performance is in no way
      comparable with more fullsized antennas but for special
      applicatios the features could be interesting. For instance
      realising some capacitive feedback from the vicinity of the
      antenna rod could result in a small low power beacon with
      integrated matching - it even could be used as a presence detector
      with direkt frequency read out ... <br>
    </p>
    <p>- But yes, Rik, I`ll certainly will keep my Marconi - making QSOs
      on VLF costs enough efforts even when using a big antenna. But
      I=C2=B4ve alredy orderd some VLF crystals on the bay ...</p>
    <p>73 es Happy Easter!</p>
    <p>Tom, DK1IS<br>
    </p>
  </body>
</html>

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