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From: Markus Vester <markusvester@aol.com>
Message-Id: <8D15DE209075531-27BC-8C12@webmail-m293.sysops.aol.com>
Date: Tue, 24 Jun 2014 12:39:43 -0400 (EDT)
Subject: Re: LF: VLF in Canada
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&gt; If you cut the bottoms out from the buckets...
... already done: http://df6nm.bplaced.net/VLF/pictures/coil_opened_for_air=
flow.jpg
Actually=C2=A0thought of putting a fan on the top=C2=A0and feed it=C2=A0ind=
uctively, but not sure how the motor electronics would handle the fields.
=C2=A0
&gt; I could not get to the arced coil .JPG
You should be able to browse the folder http://df6nm.bplaced.net/VLF/pictur=
es/=C2=A0-=C2=A0seems to work from here.=C2=A0
=C2=A0
The=C2=A0flashover had happened=C2=A0a couple of weeks ago during a long un=
attended transmission. The buckets had been pushed=C2=A0all the way in=C2=
=A0to bring the resonance from 8.97 to 8.27 kHz, in a silly attempt to prot=
ect the Euclid lightning locator network against=C2=A0undue interference fr=
om my superstrong microwatts (ha ha). In the meantime, I have repaired the =
faulty coil, increased=C2=A0the antenna capacitance a bit by doubling up so=
me more parts of the antenna wire, and=C2=A0inserted=C2=A0a few=C2=A0fat ch=
unks of ferrite in the coil (more pics in above directory). So=C2=A0I'm bac=
k to=C2=A0"safe 4-Lego=C2=A0spacing" at the new frequency (at least I think=
 so ;-)
=C2=A0
73,=20
Markus
=C2=A0


-----Urspr=C3=BCngliche Mitteilung-----=20
Von: stan, W1LE &lt;stanw1le@verizon.net&gt;
An: rsgb_lf_group &lt;rsgb_lf_group@blacksheep.org&gt;
Verschickt: Di, 24 Jun 2014 3:12 pm
Betreff: Re: LF: VLF in Canada

Hello Markus,

Interesting post about your coil.
If you cut the bottoms out from the buckets,=20
would you have better convective air flow for cooling the coils ?
Like a chimney effect.

I am starting to think about 9KHz operations. An interesting challenge.

I could not get to the arced coil .JPG. Do you have a better web address ?

Stan, W1LE=C2=A0=C2=A0=C2=A0 Cape Cod=C2=A0=C2=A0 FN41sr


On 24-Jun-14 6:55 AM, Markus Vester wrote:

Joe, good to read this!=20
=C2=A0
Regarding the loading coil, I would agree with Stefan that a large multitur=
n air coil is the best option. A laminated iron core would suffer from exce=
ssive eddy current losses, and the effect of ferrites is limited by saturat=
ion and hysteresis losses.
=C2=A0
My 1.3 henry coil consumed 2.3 km of 0.4 mm enameled wire, using 7 buckets =
with 480 turns on each:
df6nm.bplaced.net/VLF/VLF_110304-06/coil_legospacers.jpg.
The advantage is that due to magnetic coupling between layers, you will nee=
d less wire for a given inductance. And the inductance is adjustable across=
 a wide range, using spacers. Disadvantages are the high electric field bet=
ween layers limiting voltage capability, and less effective heat removal fr=
om the inner buckets. Stuffing the buckets too tightly into one another is =
surely not a good idea:
df6nm.bplaced.net/VLF/pictures/arced_coil_140601.jpg
=C2=A0


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<div><SPAN style=3D"DISPLAY: inline-block" contentEditable=3Dfalse></SPAN>&=
gt; If you cut the bottoms out from the buckets...</div>


<div>... already done: <A href=3D"http://df6nm.bplaced.net/VLF/pictures/coi=
l_opened_for_airflow.jpg">http://df6nm.bplaced.net/VLF/pictures/coil_opened=
_for_airflow.jpg</A></div>


<div>Actually&nbsp;thought of putting a fan on the top&nbsp;and feed it&nbs=
p;inductively, but not sure how the motor electronics would handle the fiel=
ds.</div>


<div>&nbsp;</div>


<div>&gt; I could not get to the arced coil .JPG</div>


<div>You should be able to browse the folder <A href=3D"http://df6nm.bplace=
d.net/VLF/pictures/">http://df6nm.bplaced.net/VLF/pictures/</A>&nbsp;-&nbsp=
;seems to work from here.&nbsp;</div>


<div>&nbsp;</div>


<div>The&nbsp;flashover had happened&nbsp;a couple of weeks ago during a lo=
ng unattended transmission. The buckets had been pushed&nbsp;all the way in=
&nbsp;to bring the resonance from 8.97 to 8.27 kHz, in a silly attempt to p=
rotect the Euclid lightning locator network against&nbsp;undue interference=
 from my superstrong microwatts (ha ha). In the meantime, I have repaired t=
he faulty coil, increased&nbsp;the antenna capacitance a bit by doubling up=
 some more parts of the antenna wire, and&nbsp;inserted&nbsp;a few&nbsp;fat=
 chunks of ferrite in the coil (more pics in above directory). So&nbsp;I'm =
back to&nbsp;"safe 4-Lego&nbsp;spacing" at the new frequency (at least I th=
ink so ;-)</div>


<div>&nbsp;</div>


<div>73, </div>


<div>Markus</div>


<div>&nbsp;</div>


<div><br>
</div>
-----Urspr=C3=BCngliche Mitteilung----- <br>
Von: stan, W1LE &lt;stanw1le@verizon.net&gt;<br>
An: rsgb_lf_group &lt;rsgb_lf_group@blacksheep.org&gt;<br>
Verschickt: Di, 24 Jun 2014 3:12 pm<br>
Betreff: Re: LF: VLF in Canada<br>
<br>


<div id=3DAOLMsgPart_1_b9b87329-c62c-4f7a-8f46-da0eeb0aeb55>

<div class=3DaolReplacedBody text=3D"#000000" bgcolor=3D"#FFFFFF">

<div class=3Daolmail_moz-cite-prefix>Hello Markus,<br>
<br>
Interesting post about your coil.<br>
If you cut the bottoms out from the buckets, <br>
would you have better convective air flow for cooling the coils ?<br>
Like a chimney effect.<br>
<br>
I am starting to think about 9KHz operations. An interesting challenge.<br>
<br>
I could not get to the arced coil .JPG. Do you have a better web address ?<=
br>
<br>
Stan, W1LE&nbsp;&nbsp;&nbsp; Cape Cod&nbsp;&nbsp; FN41sr<br>
<br>
<br>
<br>
On 24-Jun-14 6:55 AM, Markus Vester wrote:<br>
</div>

<BLOCKQUOTE type=3D"cite">

<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">Joe, good =
to read this! </div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">&nbsp;</di=
v>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">Regarding =
the loading coil, I would agree with Stefan that a large multiturn air coil=
 is the best option. A laminated iron core would suffer from excessive eddy=
 current losses, and the effect of ferrites is limited by saturation and hy=
steresis losses.</div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">&nbsp;</di=
v>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">My 1.3 hen=
ry coil consumed 2.3 km of 0.4 mm enameled wire, using 7 buckets with 480 t=
urns on each:<br>
df6nm.bplaced.net/VLF/VLF_110304-06/coil_legospacers.jpg.<br>
The advantage is that due to magnetic coupling between layers, you will nee=
d less wire for a given inductance. And the inductance is adjustable across=
 a wide range, using spacers. Disadvantages are the high electric field bet=
ween layers limiting voltage capability, and less effective heat removal fr=
om the inner buckets. Stuffing the buckets too tightly into one another is =
surely not a good idea:<br>
df6nm.bplaced.net/VLF/pictures/arced_coil_140601.jpg</div>


<div style=3D"FONT-FAMILY: arial; COLOR: black; FONT-SIZE: 10pt">&nbsp;</di=
v>
</BLOCKQUOTE><br>
</div>
</div>

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