Message-ID: <98C09BB1F3184387904CD2E8F05043E2@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <3610102492.20180308120003@gmail.com>
Date: Thu, 8 Mar 2018 13:55:20 -0000
MIME-Version: 1.0
Subject: LF: Re: Can an air cored LPF inductor have as high a "Q" as a toroidal wound one?
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Chris my take on this.....not having used this level of power at LF.....if 
the core is gettting hot it is not providing a particularly high Q !! My 
line is that LPF are best made with air cored inductors, the values required 
are not so high as to need ferrite. (see MRF and YXM filters) It does mean 
care in layout to avoid coupling between the stages.  You may even be able 
to use a non-magnetic toroidal core!  Current sensing transformers at Rugby 
GBR 16kHz  (similar to the transformers in Jim Moritz scopematch) were wound 
on discs of Tufnol  (SRBF)

One thought I dont know the answer to.......magnetisation is not a linear 
effect, if you are getting heating you are into the saturation 
area......what does his non-linearity do to the signal ! It may even 
compromise the effect your are trying to obtain ......actually generating 
harmonics??

Alan
G3NYK

----- Original Message ----- 
From: "Chris Wilson" <dead.fets@gmail.com>
To: <rsgb_lf_group@blacksheep.org>
Cc: <dead.fets@gmail.com>
Sent: Thursday, March 08, 2018 12:00 PM
Subject: LF: Can an air cored LPF inductor have as high a "Q" as a toroidal 
wound one?


>
>
> Hello  expert LF'ers!
>
> The  centre  toroid  of  my  three  toroid  LPF heats up on the longer
> transmissions  like  WSPR15.  I  have  added  a  small fan as a crutch
> (thanks  N1BUG!) but I guess that's a crutch for inadequate hardware. I
> was  wondering  whether  instead of buying a larger toroid, which seem
> only  to  be  available  from the US at high cost, I could wind an air
> cored  coil  of  similar  inductance. But I am unsure whether it would
> have the required "Q" factor. Your opinions please? Thanks,
>
> Also  I  am  wondering,  looking  at the Micrometals site, whether the
> current -2 material can be bettered by using -3 material?
>
> http://www.w1vd.com/LPF.pdf
>
> and info on frequency range of these cores is at: http://toroids.info/
>
>
>
> -- 
> Best regards,
> Chris                          mailto:dead.fets@gmail.com
>
>