Message-ID: <B4BD637350C7488DA8A8BAF58FC09D7D@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <CAKvcm2dbFX3d+jv04M_quU0Nwy=W-g5Jk5vxcN5SP87gg3PmzA@mail.gmail.com> <B507F4F2886F4488A919515FDD664BC3@gnat>
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Date: Fri, 15 Feb 2013 11:47:46 -0000
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Subject: Re: LF: Re: how to increase the Q of my loading coil?
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I would  go  along with  that

I would think the  higher the  Q  the  higher the  losses in such a coil , 
the  bigger the  circulating  values ..  I look at 500  as the  next  band 
down  from   160  , differing  set of  rules  than  coming  up from  136 
..Top coil , takes  the  voltage out of the  shack / tuner house , while 
increasing the  vertical  amps , and yes, rain + Q =  problems !

Ground is more  important than the  wire in the air or the tuner losses 
....... all  the  old (now very old)  marine  installations  only  had  30 
or 40  feet  of  vertical   wire  from the  radio  room  roof  to the   top 
wire , but  a few  1000's   tons  of  iron  and  salt water  to  tune 
against

GL-73-G..





--------------------------------------------------
From: "Alan Melia" <alan.melia@btinternet.com>
Sent: Friday, February 15, 2013 1:28 AM
To: <rsgb_lf_group@blacksheep.org>
Subject: LF: Re: how to increase the Q of my loading coil?

> 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
>>
>
>