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Author Topic: What Ferride toroid to use.  (Read 2786 times)
N4NDX
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Posts: 217




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« on: October 31, 2017, 11:17:16 AM »

I want to home-brew a Dual Core Isolation Balun 1.5-54 Mhz, 5kW for my Force12 XR5 Yagi  which core should I use. Any info will be appreciated.

73 de N4NDX

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KM1H
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Posts: 2593




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« Reply #1 on: October 31, 2017, 02:06:30 PM »

Since that antenna only covers 20-10 you dont need such a broadband balun. The 43 mix is fine as the Fair-Rite 2631803802 available at Mouser for $6.03 each depending on power used

The photo is wrong
https://www.mouser.com/ProductDetail/Fair-Rite/2631803802/?qs=P8bU7i9nNAWMk1EJQzshLg%3D%3D

Carl
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N4NDX
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Posts: 217




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« Reply #2 on: October 31, 2017, 06:26:52 PM »

Thanks Carl
So I can use 2  FT240-43 ferrite toroid stacked one on top of the other?
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NK7Z
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« Reply #3 on: October 31, 2017, 08:21:29 PM »

I wrap FT-240-43s in 3M Fiberglass tape, then wrap double polyimide insulated wire on that.  See:

http://www.karinya.net/g3txq/chokes/

for more details on how to wrap it.
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
W6EM
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Posts: 1665




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« Reply #4 on: October 31, 2017, 08:22:17 PM »

Since that antenna only covers 20-10 you dont need such a broadband balun. The 43 mix is fine as the Fair-Rite 2631803802 available at Mouser for $6.03 each depending on power used

The photo is wrong
https://www.mouser.com/ProductDetail/Fair-Rite/2631803802/?qs=P8bU7i9nNAWMk1EJQzshLg%3D%3D

Carl
That number is incorrect.

The Fair-Rite number sequence for toroids start with "59." The mix is next.  So, should be followed by "43," if that's the mix you want.  Fair-rite says 43 is only recommended below 10MHz in transformer applications.  If you want a 2.4 inch, mix 61 core, which can be used for 14 and 28 MHz transformers, that would be a Fair-rite 5961003801.

Yes, you can stack them.  Just assume you have twice the core area, so you won't need as many turns.  Keep in mind that the permiability is 125, not 800, so increase the turns accordingly.



  
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NK7Z
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« Reply #5 on: October 31, 2017, 08:29:17 PM »

The Fair-Rite number sequence for toroids start with "59." The mix is next.  So, should be followed by "43," if that's the mix you want.  Fair-rite says 43 is only recommended below 10MHz in transformer applications.  If you want a 2.4 inch, mix 61 core, which can be used for 14 and 28 MHz transformers, that would be a Fair-rite 5961003801.
Do you have a source for this?  I would like to get this info for my home Wiki.
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
WB6BYU
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Posts: 17171




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« Reply #6 on: October 31, 2017, 08:53:33 PM »

Quote from: N4NDX

...a Dual Core Isolation Balun...



Are you wanting a 1 : 1 current balun?  Those can be wound on a single core.
Is there a particular reason you specified dual core?  Are you imagining just stacking
two cores together, or two windings on separate cores?  Or a pair of ferrite sleeves
side-by-side to mimic a 2-hole core?

A 4 : 1 current requires two cores, with separate windings on each core.  But
that doesn't sound like what you want to build for that specific application.

Is there a particular reason you need wider operating bandwidth than the antenna
itself covers?


I ask these questions because it helps us to better understand what you are trying
to accomplish, so we can better help you in the process.
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K8AXW
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Posts: 6360




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« Reply #7 on: October 31, 2017, 09:35:36 PM »

BYU:  I don't want to highjack this thread so after you and others get this guy on the right track I need a question answered.

That question is:  How do you know if you have the minimum 20db of attenuation across the HF spectrum without a spectrum analyzer?

The SWR across the same spectrum is easy to determine.

(On subject, from what I have learned, 2 FT240-43 cores stacked and initially held together by clear packing tape on the outside edge and then the windings of Teflong wire will handled over a KW.  If one core is used the  power limit would be about half of that.)

 
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KM1H
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Posts: 2593




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« Reply #8 on: November 01, 2017, 08:35:13 AM »

Quote
That number is incorrect.The Fair-Rite number sequence for toroids start with "59." The mix is next.  So, should be followed by "43," if that's the mix you want.  Fair-rite says 43 is only recommended below 10MHz in transformer applications.  If you want a 2.4 inch, mix 61 core, which can be used for 14 and 28 MHz transformers, that would be a Fair-rite 5961003801.

We are NOT discussing transformers here and it is the number Ive been using for almost two decades for 43 and 31 mix for 160-6M and I find 61 mix useless at HF which is confirmed below as too "peaky" for repeatability. The link also uses the 26 prefix and is a 2016 revision.
http://audiosystemsgroup.com/RFI-Ham.pdf

Perhaps Fair-Rite has recently changed numbers as the applications between 31 and 43 mix were different in their catalogs and caused some confusion.

Carl
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N4NDX
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Posts: 217




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« Reply #9 on: November 01, 2017, 10:50:46 AM »

According to the link below Carl KM1H suggestion is clear that 43-31 mix are the ones to use for my antenna.

http://www.karinya.net/g3txq/chokes/


-This is the reason for my initial question of going with double core instead of one. Check the link below specifications. I'm not trying to save a buck by doing it.  I just want to be able to say I did it Homebrew.

http://www.balundesigns.com/model-1115d-max-choking-1-1-balun-1-5-54-mhz-5kw/
« Last Edit: November 01, 2017, 11:14:23 AM by N4NDX » Logged
W9IQ
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Posts: 1708




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« Reply #10 on: November 01, 2017, 11:17:53 AM »

Quote
s there any benefit on going 2 core or a single core will do as well.

Keep in mind that any deviations from the G3TXQ construction details will alter the effective frequencies and the choking performance. So adding another core will "take you off the chart". The same applies to the type of coax that you use - in particular the outer conductor diameter and jacket characteristics are critical to the indicated results. You would then need to conduct your own measurements using a vector impedance analyzer or similar in order to be assured as to the effectiveness of your new design.

In a more general sense, adding a second core would improve the maximum common mode current that the balun can successfully dissipate as power and it should reduce the number of turns required to deliver a comparable choking impedance.

One of the variables in coax on ferrite chokes is the interwinding capacitance. This appears as a capacitance in parallel with the inductor formed by the turns through the toroid. Interwinding capacitance is notoriously difficult to predict mathematically with any degree of accuracy. It is typically dealt with from an experimental perspective. A lot of Steve's chart reflects the nature of these factors.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
N4NDX
Member

Posts: 217




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« Reply #11 on: November 01, 2017, 11:49:53 AM »

Thanks Glenn

I think I'm going to follow the simple single core from G3TXQ Common-mode chokes.

I appreciate all the help from this forum.

73 de David/N4NDX
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W6EM
Member

Posts: 1665




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« Reply #12 on: November 01, 2017, 12:51:14 PM »

The Fair-Rite number sequence for toroids start with "59." The mix is next.  So, should be followed by "43," if that's the mix you want.  Fair-rite says 43 is only recommended below 10MHz in transformer applications.  If you want a 2.4 inch, mix 61 core, which can be used for 14 and 28 MHz transformers, that would be a Fair-rite 5961003801.
Do you have a source for this?  I would like to get this info for my home Wiki.
http://www.fair-rite.com/product-category/inductive-components/toroids/
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W6EM
Member

Posts: 1665




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« Reply #13 on: November 01, 2017, 01:00:21 PM »

Quote
That number is incorrect.The Fair-Rite number sequence for toroids start with "59." The mix is next.  So, should be followed by "43," if that's the mix you want.  Fair-rite says 43 is only recommended below 10MHz in transformer applications.  If you want a 2.4 inch, mix 61 core, which can be used for 14 and 28 MHz transformers, that would be a Fair-rite 5961003801.

We are NOT discussing transformers here and it is the number Ive been using for almost two decades for 43 and 31 mix for 160-6M and I find 61 mix useless at HF which is confirmed below as too "peaky" for repeatability. The link also uses the 26 prefix and is a 2016 revision.
http://audiosystemsgroup.com/RFI-Ham.pdf

Perhaps Fair-Rite has recently changed numbers as the applications between 31 and 43 mix were different in their catalogs and caused some confusion.

Carl
Carl:  Not trying to be argumentive here, but clearly, if you go to fair-rite's site and browse, you'll see their catalog under "inductive-components, closed-circuit" to include details on all of their toroidal cores.  http://www.fair-rite.com/product-category/inductive-components/toroids/

I'm puzzled when you say that we're not discussing transformers here.  Clearly, a closed-circuit core with windings amounts to a transformer.  Whether a current or voltage transformer balun depends on how it/they  are designed and connected to the transmission line.

Fair-rite does make a line of suppressor cores, not to be confused with the toroids.  Mainly since their dimensions, not the materials, are suitable for slip-over-the-cable applications.

I'll slide out of here as the conversation has moved on.  But, hate to see someone spend upwards of $10, including shipping, for a slip on attenuator and not a toroid core.

Mouser is about the best price for most Fair-rite cores, but you have to come equipped with the FR catalog number to be sure.

73.

Lee
W6EM
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NK7Z
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Posts: 1844


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« Reply #14 on: November 01, 2017, 01:01:40 PM »

Thanks Glenn

I think I'm going to follow the simple single core from G3TXQ Common-mode chokes.

I appreciate all the help from this forum.

73 de David/N4NDX

I have several chokes like this using single core I have constructed, and none of them exhibit any changes during KW level operations, which implies they are not heating up, which implies they are good a KW levels.  SWR ranges are all below 2:1 at the antenna base.
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
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