[TowerTalk] New tool - toroidal ferrite core inductor calculator

[Jim Brown]

Note that it matters greatly the ORDER in which turns pass through the 
toroid core. Out of order turns (that overlap each other, what happens 
with scramble winding) cancel each other. This one of the things I 
learned during the extensive (2 years) research for the 2018 Cookbook.

73, Jim K9YC

On 6/21/2021 9:10 AM, jim.thom jim.thom at telus.net wrote:
> Date: Thu, 17 Jun 2021 16:15:34 -0700
> From: Dan Maguire <danac6la at gmail.com>
> To: towertalk <towertalk at contesting.com>
> Subject: Re: [TowerTalk] New tool - toroidal ferrite core inductor
>          calculator
> 
> 
> Jacek, SP3L, had some trouble posting so he asked me to relay his
> answers to a few of the questions posed by VE7RF.  -  Dan, AC6LA
> 
> ====================================
> 
> 
> Here are my answers to VE7RF questions.
> 
>>>> I noticed it will only handle a maximum of 3 x cores, why is that ? I
> use 5 x cores, type 31, 2.4 inch OD on both my 160 and also 80 and also
> 40mCM chokes.
> 
> Using N cores does not increase the inductor impedance. Actually, it
> even slightly reduces it. Try calculating and displaying the following
> inductors:
> 1x #43: 2.4/0.5" 14T
> 2x #43: 2.4/0.5" 9T
> 3x #43: 2.4/0.5" 7T
> 
> [AC6LA:  See
> https://forums.qrz.com/index.php?threads/new-tool-toroidal-ferrite-core-inductor-calculator.768222/page-5#post-5888198
> ]
> 
> If you increase the number of cores, you need fewer turns to achieve
> the same frequency coverage and your core has greater volume so it can
> dissipate more power. And that's it.
> 
> But if you take the same 3 cores, wind them individually and connect
> them in series - that's quite another story. Your total choke
> impedance will increase 3 times (both |Z| and R). That reduces both
> the common-mode current and power that needs to be dissipated in the
> choke. And you again have three cores to dissipate heat but as said
> before less heat than before.
> 
> One more thing. Suppose that you calculated that every individual
> chokes should have, say, 14 turns. You may decide to make three chokes
> having 13, 14 and 15 turns and connect them in series. In this way,
> your final choke will tolerate the spread of core permeability
> parameters to a higher degree.
> 
> That's why I do not see much benefit in increasing the number of cores
> in the calculator.
> 
> 
> 
>>>> As per number of turns, is this for wire, or coax,  or can be used for
> either ?   If coax used, what type of coax ?   I used  RG-303 and  RG-400
> on the smaller  CM chokes....and  RG-393 on the bigger CM chokes.
> 
> Generally it is for insulated wire but I do not expect a significant
> difference if you use coax.
> 
> 
> 
> 
> ###  Tnx for the prompt reply.   The reason I mentioned about the use of
> more than 3 x cores is in my case, I have  200 feet of  RG-393  teflon
> coax  available, and  the max number of turns that will fit inside a  2.4
> inch  OD  core is 7.  Thats  7 passes through the cores,  before coax
> terminations   are made.   213-U is the same deal, only 7  turns max, with
> no connectors.
> 
> ##  The  160 and 80 m  cm chokes are both made with  7 turns of  RG-393 on
> 5 x type 31,  2.4 inch OD cores.   Thats 5 k ohms on 160m, 7.6 k on
> 80m...and  5 k ohms on  40m.    The  actual 40m cm choke is made with only
> 6 turns on 5 x cores..which results in 6.2 k ohms....so slightly higher by
> 1.2 k ohms, with one less  turn.
> 
> ##  I used  2 x identical CM  choke assys  in series, each in its own
> 8x8x4  nema box, with gasketed lid etc.   On paper, this should result in
> 10k on 160m,   and  15.2 k on  80m, and  12.4 k  on 40m.   The goal was to
> get at least  10 k.... which should result in  a 40db  reduction  in  CM
> current.  If gasketed nema boxes are used, put some Permatex  dielectric
> grease on the rubber gasket, before closing the lid.  Mine are all air
> tight..and filled with a large package of silica gel / desiccant.   I only
> operate at night, so solar effects are a non issue.  If I have done the
> maths correctly, the actual dissipation of the stack of  5 x  cores in each
> box is miniscule.
> 
> ##  On a side note, I have one of  danny horvath's CM chokes  which covers
> 160-10m.  It consists of  9 turns of RG-303 on 2 x type 31,  2.4 inch OD
> cores.... which is then in series with 12 turns of 303 coax, on another 2 x
> cores.  Both stacks go into the same box.  7.7 k on 160, which then
> increases a bunch, like 8.8 k  on 80m..and keeps increasing, as freq
> increases to a max of  11-12 k on 12m..then back down to 10 k on 10m.   On
> each band,  RS is >  XS, which was the goal.
> 
> ## heres  what does not work very well, and thats a binoc  configuration.
> We managed to get one to  cover 3.2  to  4.4 mhz....and thats it... like
> 6.4 k.   Useless on  7 mhz/  40m band.   Binoc configs are extremely narrow
> banded, and very tricky to get to work....like work on one band.   I dont
> recommend them.
> 
> Jim   VE7RF
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