Message-ID: <511D8ACE.2010500@iup.uni-heidelberg.de>
Date: Fri, 15 Feb 2013 02:09:34 +0100
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <Stefan.Schaefer@iup.uni-heidelberg.de>
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Subject: Re: LF: how to increase the Q of my loading coil?
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Hi Dimitris,

Am 15.02.2013 01:52, schrieb Dimitrios Tsifakis:
> Hi Stefan,
>
> A photo of the coil can be seen here:
>
> http://people.physics.anu.edu.au/~dxt103/500/
>    
That big wire is standard house electrical wire for 240V in VK? Looks 
like 4...6 mm^2 :-) Rated at 35A? :-)

Well, i would wind ll the turns without the gaps. That makes it more 
compact and the coupling will be better. So the L will be higher and so 
you will need less wire and get a higher Q. I would keep the distance to 
ground at least the diameter of the bucket. The diameter/length will be 
quite good.

A Q of 220 is not bad. You may rise it to 300 with that type of wire i 
think.

> The operating position is inside a little metal garden shed. I have a
> wooden bench and it sits on that. There is maybe 0.5 m of space or
> more between the inductor and the shed walls.
>    
OK, that is good. But the wire, who do you bring it outside? Maybe there 
is a significant C between the wire and the coil to the walls anyway, in 
relation to the antenna C.

> Ground losses are estimated to be a bit less than 20 ohm. This varies
> a bit with the WX, currently after a bit of  rain think it is probably
> around 17 or 18 ohm. There is clay under the soil, which I think is
> good news when it comes to conductivity :-)
>
> Going from 27 ohm to say (Q=1000) about 20 ohm antenna impedance,
> would result in a small but very welcome antenna current increase...
>    
And what about the radiation resistance? Have you already reached the limit?

73, Stefan

> 73, Dimitris
>