[RFI] Fwd: Re: [TowerTalk] Snap-on Ferrites

[Dave Cole]

Jim,

Thanks for the insight on the snap ons vs., the solid core ferrite 
materials...  I have always thought that the snap-ons were significantly 
less effective than the solid cores.  No tests, just one of those 
assumptions that creep into mindsets.  Thanks for the clarification.

73s and thanks,
Dave
NK7Z
http://www.nk7z.net

On 06/19/2017 09:50 AM, Jim Brown wrote:
> John cross-posted his original question to both TowerTalk and the RFI
> list. I saw it on the TowerTalk first, and responded there. Here's my post.
>
> 73, Jim K9YC
>
> -------- Forwarded Message --------
> Subject:     Re: [TowerTalk] Snap-on Ferrites
> Date:     Sun, 18 Jun 2017 23:33:44 -0700
> From:     Jim Brown <jim at audiosystemsgroup.com>
> Reply-To:     jim at audiosystemsgroup.com
> To:     towertalk at contesting.com
>
>
>
> On Sun,6/18/2017 10:06 PM, VE1DT wrote:
>> I have again reviewed the tutorial (Rev 6 Dec 2016) and found the
>> paragraph
>> that does indeed repeat what you refer to. I thought that basically
>> only the
>> material mattered, not the shape. So, if we are comparing #31 toroids
>> to #31
>> Clamp-Ons, they are basically going to give about the same results.
>
> I've noted that, in general, impedance is proportional to the length of
> the core that a single turn of the conductor passes through.  And yes,
> this depends upon the material. It also STRONGLY relates to the number
> of turns.  Those relationships are clearly addressed in the tutorial
> (but you've got to STUDY it, not just skim it looking for the answer to
> a narrow question).
>
>> You also "recommend" many Big #31 Clamp-on options for HF usage in your
>> cookbook. In fact, there are also other places in the tutorial where the
>> clamp-on chokes are discussed and yet none of the sections say that the
>> Clamp-On is a poor choice for usage at HF.
>
> I do not share Joe's concerns about the small air gap for clamp-ons that
> are manufactured to very good "flatness" or whatever the correct word is
> to define the perfection with which the mating surfaces can meet.
> Fair-Rite data sheets show very little divergence between clamp-on and
> solid cylinders having the same dimensions. I'd probably change my mind
> if I saw what I believed to be credible data showing that they ARE
> significantly different when they come off the production line. :)
>
> What the article probably was saying (and I haven't read it) is that
> string of beads chokes don't work unless that material is like Fair-Rite
> #73, which is what W2DU correctly chose for his first chokes. Most
> ferrite beads are resonant in the high VHF range. As the tutorial shows,
> an effective choke is self resonant at the frequency where suppression
> is required.
>
> My tutorials develop these concepts. I encourage all to study it. I
> spent a lot of time learning it and writing about it, and I refuse to
> repeat it here for those who are too lazy to study what I've written for
> them! The first tutorial, from 2010, is k9yc.com/RFI-Ham.pdf  Another,
> which ran in National Contest Journal last year, is
> http://k9yc.com/KillingReceiveNoise.pdf  It offers a conceptual
> discussion of how ferrite chokes work in a sidebar.
>
> 73, Jim K9YC
>>
>>
>> In reviewing Appendix 1, I cannot see how the #31 Big Clamp-On is a bad
>> choice. The first 4 Manufacturer's Published Data charts in Appendix 1
>> seem
>> to show about the same performance between circular and clamp on cores.
>>
>>
>> Comparing the 2.4" OD toroid against the Big #31 Clamp-On seem to provide
>> similar data.
>>
>> #31 Toroid: Impedance/ESR - 5 turns (Dark red curve) peak at about 1,500
>> ohms
>>
>> #31 Clamp-On: Impedance/ESR - 5 turns (Dark red curve) peaks at about
>> 3,000
>> ohms
>>
>>
>> Here's another section where you certainly don't have anything bad to say
>> about Clamp-Ons.
>>
>>
>> The Big Clamp-Ons appear to be expensive but they're not - one is roughly
>> equivalent to three or
>>
>> toroids! They are wonderful for portable and Field Day operations,
>> because
>> you can easily apply
>>
>> them to coax without taking the connector off. There is another
>> advantage -
>> chokes for 160-40
>>
>> meters using the Clamp-On weigh about a half pound less than one using
>> toroidal cores.
>>
>>
>> Color me confused. Where have I gone astray?
>>
>>
>>
>>> Gerald, VE1DT
>>
>>
>>
>>
>>
>> He's absolutely correct. Many times I've posted a link to my tutorial
>> on the
>> topic. I spent years learning how this stuff works, and months writing it
>> up. I won't repeat it here. Only the link. k9yc.com/RFI-Ham.pdf
>>
>>
>> 73, Jim K9YC
>>
>>
>> On Sun,6/18/2017 7:44 PM, john at kk9a.com wrote:
>>
>> I was reading the recent QST article RF Mayhem by WB8IMY. The author
>> said to
>>
>> avoid using snap-on ferrites for problems caused by HF signals as they
>>
>> rarely work well at HF. It is best to stick with circular cores.
>>
>>
>> Is this correct?  I was not aware that snap-ons were less effective.
>>
>>
>> John KK9A
>>
>> _______________________________________________
>>
>>
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