Message-ID: <B507F4F2886F4488A919515FDD664BC3@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <CAKvcm2dbFX3d+jv04M_quU0Nwy=W-g5Jk5vxcN5SP87gg3PmzA@mail.gmail.com>
Date: Fri, 15 Feb 2013 01:28:57 -0000
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Subject: LF: Re: how to increase the Q of my loading coil?
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Why? I think you might need to look at the priorities first. Experience says 
you will not notice the difference unless you have tackled the problem of 
ground and environmental losses first (as Stefan has done) The improvement 
obtained by improving the Q of the loading coil may probably only increase 
the efficiency by a minute amount.

You say you have a Q of 200 now.... this indicates a bandwidth of about 2kHz 
meaning you will probably need to retune across the band. A Q of 400 to 500 
should be possible but unless the reduction in RF resistance is a 
substantial fraction of the Rloss it is wasted effort. It also means that 
your tuning will be very weather dependent. I feel that unles you have 
situation of Rloss <15ohms you will barely notice the difference......except 
a "flighty" system, difficult to keep peaked, and possibly a number of fried 
PA devices when it goes wrong.

Litz will improve the Q slightly, coil form factor needs to be right as 
well, and Litz is a devil to work with (note "proper" Litz has strand 
numbers are twisted in powers of 3, anything else is just bundled and will 
not achieve the theoretical advantage) If you miss one strand out of the 
soldered connection of the Litz you will lose a lot of the advantage.

Top loading may well turn out to be more effective, but it all depends on 
your partcular location, and you need to make measurements of the antenna 
systtem, and possibly the field it generates, not guess (though that is very 
seductive :-)) but in my experience is usually wrong!  )

You are right in that the best way is to make incremental improvements to 
the antenna, but be very critical, weighing the cost in effort and cash for 
the improvement .......what works for others may not work for you.

Best of Luck
Alan
G3NYK

----- Original Message ----- 
From: "Dimitrios Tsifakis" <dtsifakis@gmail.com>
To: <rsgb_lf_group@blacksheep.org>
Sent: Friday, February 15, 2013 12:31 AM
Subject: LF: how to increase the Q of my loading coil?


> Hello group,
>
> I would like to increase the Q of my loading coil for 475 kHz. . It
> consists currently of a 20-litre plastic bucket with standard house
> 240V electrical wire (with PVC jacket). I measured the Q and found it
> to be about 220 (XL is about 2 kohm). I do have  some Litz wire I can
> use. I also have a piece of large diameter (25 cm) storm water pipe,
> which I think is made of PVC.  Would you recommend using a PVC former
> or should I look for a more exotic material (glass/porcelain)? Would
> you think the inter-turn capacitance is very detrimental and some
> exotic winding technique would yield better results?
>
> I understand that ground losses are bigger in my case than the
> inductor losses, but I would like to address the inductor first.
>
> 73, Dimitris VK1SV
>