Message-ID: <15805f47723.marcocadeddu@tin.it>
Date: Thu, 27 Oct 2016 13:44:17 +0200 (CEST)
From: "marcocadeddu@tin.it" <marcocadeddu@tin.it>
To: <rsgb_lf_group@blacksheep.org>
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Subject: R: Re: ULF: A new step on the large ULF coil...
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Bravo Stefan :-)
at a first glance I supposed the bike had to provide rotation of the 
coil support!
Anyway the coil looks really pretty considering the 
number of turns and the thin wire used again compliments!

Keep on with this nice work and we dream to listen to you soon on the 
dreamer band

73 de Marco IK1HSS

----Messaggio originale----
Da: selberdenken@posteo.de
Data: 27-ott-2016 12.28
A: <rsgb_lf_group@blacksheep.org>
Ogg: Re: ULF: A new step on the large ULF coil...

Hi Luis,

Am 27.10.2016 11:40, schrieb VIGILANT Luis Fernández:
> Amazing work Stefan !! :-O
> I bet you have constructed some kind of support (like a lathe) which 
> lets you rotate the pipe easily and wound the coils . Right ?
Right! See: 
https://dl.dropboxusercontent.com/u/19882028/ULF/20160702_222257.mp4
It's quite comfortable but still a lot of work.
> This is getting really heavy and the quality of coils looks very 
nice 
> and repeteable ...... at least five times ! ;-)
5 kg of copper wire so far. Still quite managable.
> Dumb question: Why do you get different inductance values when 
> resonating it with antenna equivalent capacitor and when measuring 
> current at 273V AC / 50Hz  ??
> Shouldn't be inductance a constant value ? ...... or I'm missing 
> something obvious :(
It's due to the inner-winding capacity which is higher than on a 
single 
layer coil. At the self-resonance frequency you need no external C to 
get this resonance, of course. Then add just 10 pF external C. The new 
resonance frequency will be almost the same. If you calculate L from 
that frequency and C, it will be a gigantic high value, several GH :-)
Assume the internal C is 100 pF. And L is 4 H. Then f res will be 
about 
7.9577 kHz. With 10 pF external it will be 7.5874 kHz. If you ignore 
the 
internal C and say "I'm getting 7.5874 kHz with just 10 pF connected 
to 
the L" you would calculate L = 44 H!
So you need to switch a much larger C in parallel to L so that the 
internal C becomes irrelevant. Maybe 1 uF, then you will get 79.6 Hz 
at 
4H. When calculating L with 1.000001 uF (1uF + 100 pF) and 79.6 Hz you 
will get 3.997 H, which is quite correct!
It doesn't need to be a resonated circuit of course. You can also 
apply 
a constant voltage and simply measure the current. But you need to 
know 
the DC resistance then. Then Z = U/I = R^2 + XL^2 and L = XL / 314 (at 
50 Hz).

> Good luck with the 6th floor. Seems that there is no room for a 7th, 
> so that's why you mentioned the variometer
I will first build the variometer now on a 16cm diameter and 6cm high 
piece of tube. Will see what the tuning range is. You know, actually 
i'm 
not a friend of calculations if i can do an experiment instead :-)

73, Stefan
> 73 de Luis
> EA5DOM
>
> 
------------------------------------------------------------------------
> *De:* owner-rsgb_lf_group@blacksheep.org 
> [mailto:owner-rsgb_lf_group@blacksheep.org] *En nombre de *DK7FC
> *Enviado el:* miércoles, 26 de octubre de 2016 19:06
> *Para:* rsgb_lf_group@blacksheep.org
> *Asunto:* Re: ULF: A new step on the large ULF coil...
>
> 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
>