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Date: Wed, 26 Oct 2016 19:05:30 +0200
From: DK7FC <selberdenken@posteo.de>
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Subject: Re: ULF: A new step on the large ULF coil...
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Hi ULF,

It's just a few weeks ago, now the *5th stack* is wound on the coil: 
*https://dl.dropboxusercontent.com/u/19882028/ULF/20161026_185804.jpg
*
The DC resistance rose from 445 Ohm to *572 Ohm*.
The measured resonance frequency (using the antenna equivalent C in the 
shack) dropped from 3.667 kHz down to *3.208 kHz*. That should be about 
*4.92 H*.
Measured at 273V AC / 50 Hz, i'm getting 197 mA, so the actual 
inductance is *4.0 H*.

A 6th stack and a variometer part is needed!

73, Stefan

Am 08.10.2016 01:30, schrieb DK7FC:
> Hi ULF,
>
> This night i have completed the 4th stack of my large ULF loading coil.
> An image: 
> https://dl.dropboxusercontent.com/u/19882028/ULF/20161008_ULF_TX_coil.jpg
>
> The exciting question was, what is the new resonance frequency 
> together with my antenna. In the lab i put an equivalent C in parallel 
> and found the resonance peak at *3.67 kHz*. So the L seems to be *3.8 
> H* now. This is still not enough. The l/d of the coil dimension 
> becomes larger now, so i need more and more wire to reach the final 
> resonance frequency of 2.97 kHz at about 500 pF.
>
> I will do a next test on the actual resonance frequency in some days, 
> when the WX permits. I will also check where the resonance can be 
> found when switching the small coil in series that i use for 6.47 kHz 
> now. It could be quite close to 2.97 kHz then! So maybe this allows a 
> next QRO step on 2.97 kHz: 100 mA antenna current must be reached for 
> the planned experiment in 65 km distance.
>
> BTW the 4 stack coil is wound out of almost 4 kg of enameled Cu wire 
> with 0.4 mm diameter. The layers are isolated by Kapton tape. My 
> assumption is that it will hold 20 kV now.
> Ah and the *DC resistance is 445 Ohm* now. When connecting 275 V AC / 
> 50 Hz, i can measure 269 mA. So the actual inductance is *2.93 H* 
> (beeing farer away from the self resonance frequency)
>
> I can tell you it's quite fascinating to operate down on these low 
> frequencies :-) To be continued...
>
> 73, Stefan/DK7FC

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Hi ULF, <br>
<br>
It's just a few weeks ago, now the <b>5th stack</b> is wound on the
coil: <b><a class="moz-txt-link-freetext" href="https://dl.dropboxusercontent.com/u/19882028/ULF/20161026_185804.jpg">https://dl.dropboxusercontent.com/u/19882028/ULF/20161026_185804.jpg</a><br>
</b><br>
The DC resistance rose from 445 Ohm to <b>572 Ohm</b>.<br>
The measured resonance frequency (using the antenna equivalent C in the
shack) dropped from 3.667 kHz down to <b>3.208 kHz</b>. That should be
about <b>4.92 H</b>.<br>
Measured at 273V AC / 50 Hz, i'm getting 197 mA, so the actual
inductance is <b>4.0 H</b>.<br>
<br>
A 6th stack and a variometer part is needed! <br>
<br>
73, Stefan<br>
<br>
Am 08.10.2016 01:30, schrieb DK7FC:
<blockquote cite="mid:57F83029.8010104@posteo.de" type="cite">
  <meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
Hi ULF, <br>
  <br>
This night i have completed the 4th stack of my large ULF loading
coil. <br>
An image: <a moz-do-not-send="true" class="moz-txt-link-freetext"
 href="https://dl.dropboxusercontent.com/u/19882028/ULF/20161008_ULF_TX_coil.jpg">https://dl.dropboxusercontent.com/u/19882028/ULF/20161008_ULF_TX_coil.jpg</a><br>
  <br>
The exciting question was, what is the new resonance frequency together
with my antenna. In the lab i put an equivalent C in parallel and found
the resonance peak at <b>3.67 kHz</b>. So the L seems to be <b>3.8 H</b>
now. This is still not enough. The l/d of the coil dimension becomes
larger now, so i need more and more wire to reach the final resonance
frequency of 2.97 kHz at about 500 pF.<br>
  <br>
I will do a next test on the actual resonance frequency in some days,
when the WX permits. I will also check where the resonance can be found
when switching the small coil in series that i use for 6.47 kHz now. It
could be quite close to 2.97 kHz then! So maybe this allows a next QRO
step on 2.97 kHz: 100 mA antenna current must be reached for the
planned experiment in 65 km distance.<br>
  <br>
BTW the 4 stack coil is wound out of almost 4 kg of enameled Cu wire
with 0.4 mm diameter. The layers are isolated by Kapton tape. My
assumption is that it will hold 20 kV now.<br>
Ah and the <b>DC resistance is 445 Ohm</b> now. When connecting 275 V
AC / 50 Hz, i can measure 269 mA. So the actual inductance is <b>2.93 H</b>
(beeing farer away from the self resonance frequency)<br>
  <br>
I can tell you it's quite fascinating to operate down on these low
frequencies :-) To be continued...<br>
  <br>
73, Stefan/DK7FC<br>
</blockquote>
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