|
Use of type 31 ferrite as coax common mode choke
I looked through saved messages and the only reference to type 31 ferrite
(Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in: http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. -- J. McLaughlin; Michigan, USA Home: |
Use of type 31 ferrite as coax common mode choke
J. Mc Laughlin wrote:
It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. Did you find any information on their fancy 'K' material? -- 73, Cecil http://www.w5dxp.com |
Use of type 31 ferrite as coax common mode choke
On Mon, 21 Apr 2008 10:21:36 -0400, "J. Mc Laughlin"
wrote: Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. Hi Mac, I can't say that I have any familiarity with type 31, but certainly the rest and others. My reference is a 13 year old hard-copy that does not have this material listed, so it is hard to make side-by-side comparisons for like-sized beads. Looking at the other charts it would seem that type 31 would have less "bulk" Z (it would take more beads at any particular frequency to equal other formulations). As for your application, and if it is a particularly long run along ground, or underground, ground itself may provide sufficient snubbing of Common Mode currents. Except, of course, 60Hz which could be particularly vicious and I would recommend running a parallel bare ground wire to the remote ground. In that regard, you may even need tri-ax. 73's Richard Clark, KB7QHC |
Use of type 31 ferrite as coax common mode choke
J. Mc Laughlin wrote:
I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in: http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. Fair-rite 31 mix is a new one specifically developed for RF choking applications. As you mention, it has a huge range of frequencies for which it's useful. The recommendations one sees in older literature for 73, 43, etc, were formulated back before the new mix was available. Of course, once something is written, it gets copied over and over without a lot of thought being put into whether the underlying assumptions are still met: in this case, what mixes are available. Page 888 in the Mouser catalog shows some 31 mix parts.. http://www.mouser.com/catalog/633/888.pdf You can also go to Fair-rite's website and find a list of their local distributors (Lodestone Pacific, for instance). The 3&4 digits of the part number are the mix: xx31yyyyyyy is a 31 mix part. |
Use of type 31 ferrite as coax common mode choke
Richard Clark wrote:
On Mon, 21 Apr 2008 10:21:36 -0400, "J. Mc Laughlin" wrote: Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. Hi Mac, I can't say that I have any familiarity with type 31, but certainly the rest and others. My reference is a 13 year old hard-copy that does not have this material listed, so it is hard to make side-by-side comparisons for like-sized beads. Looking at the other charts it would seem that type 31 would have less "bulk" Z (it would take more beads at any particular frequency to equal other formulations). I don't know about that... the 31 material is around mu=300-800 in the HF area, which is higher than the venerable 43, and a lot higher than the 61. Another advantage of the 31 material is better performance at higher temperatures. K9YC has written up a 50 odd page handbook on RFI suppression, choking, etc., with a whole raft of test data on actual chokes (bead baluns, toroids, etc.) made of various materials. http://www.audiosystemsgroup.com/RFI-Ham.pdf As for your application, and if it is a particularly long run along ground, or underground, ground itself may provide sufficient snubbing of Common Mode currents. Except, of course, 60Hz which could be particularly vicious and I would recommend running a parallel bare ground wire to the remote ground. In that regard, you may even need tri-ax. 73's Richard Clark, KB7QHC |
Use of type 31 ferrite as coax common mode choke
On Mon, 21 Apr 2008 10:21:36 -0400, "J. Mc Laughlin" wrote: SNIP P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. also check: www.palomar-engineers.com Bruce W0BF |
Use of type 31 ferrite as coax common mode choke
Dear Jim: Thanks for the handbook reference. I can not remember if I have
looked at it or not, but I sure will do so. Your material references are more recent than those of Richard. Warm regards, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Jim Lux" wrote in message ... Richard Clark wrote: On Mon, 21 Apr 2008 10:21:36 -0400, "J. Mc Laughlin" wrote: Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. Hi Mac, I can't say that I have any familiarity with type 31, but certainly the rest and others. My reference is a 13 year old hard-copy that does not have this material listed, so it is hard to make side-by-side comparisons for like-sized beads. Looking at the other charts it would seem that type 31 would have less "bulk" Z (it would take more beads at any particular frequency to equal other formulations). I don't know about that... the 31 material is around mu=300-800 in the HF area, which is higher than the venerable 43, and a lot higher than the 61. Another advantage of the 31 material is better performance at higher temperatures. K9YC has written up a 50 odd page handbook on RFI suppression, choking, etc., with a whole raft of test data on actual chokes (bead baluns, toroids, etc.) made of various materials. http://www.audiosystemsgroup.com/RFI-Ham.pdf As for your application, and if it is a particularly long run along ground, or underground, ground itself may provide sufficient snubbing of Common Mode currents. Except, of course, 60Hz which could be particularly vicious and I would recommend running a parallel bare ground wire to the remote ground. In that regard, you may even need tri-ax. 73's Richard Clark, KB7QHC |
Use of type 31 ferrite as coax common mode choke
Dear Jim:
Now I begin to see light. While type 31 must be at least three years old, the world has not yet caught up to its existence. Thanks also for the hints. Warm regards, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Jim Lux" wrote in message ... J. Mc Laughlin wrote: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in: http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. Fair-rite 31 mix is a new one specifically developed for RF choking applications. As you mention, it has a huge range of frequencies for which it's useful. The recommendations one sees in older literature for 73, 43, etc, were formulated back before the new mix was available. Of course, once something is written, it gets copied over and over without a lot of thought being put into whether the underlying assumptions are still met: in this case, what mixes are available. Page 888 in the Mouser catalog shows some 31 mix parts.. http://www.mouser.com/catalog/633/888.pdf You can also go to Fair-rite's website and find a list of their local distributors (Lodestone Pacific, for instance). The 3&4 digits of the part number are the mix: xx31yyyyyyy is a 31 mix part. |
Use of type 31 ferrite as coax common mode choke
Dear Bruce: Thank you. I shall do so. My recollection is that their
prices were on the high side, but that needs to be checked. Warm regards, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Bruce W. Ellis" wrote in message ... On Mon, 21 Apr 2008 10:21:36 -0400, "J. Mc Laughlin" wrote: SNIP P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. also check: www.palomar-engineers.com Bruce W0BF |
Use of type 31 ferrite as coax common mode choke
Dear Bruce: As a follow-up: No type 31 at Palomar. 73, Mac N8TT
-- J. McLaughlin; Michigan, USA Home: "Bruce W. Ellis" wrote in message ... On Mon, 21 Apr 2008 10:21:36 -0400, "J. Mc Laughlin" wrote: SNIP P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. also check: www.palomar-engineers.com Bruce W0BF |
Use of type 31 ferrite as coax common mode choke
J. Mc Laughlin wrote:
Dear Jim: Now I begin to see light. While type 31 must be at least three years old, the world has not yet caught up to its existence. the *amateur* world hasn't caught up.. I haven't looked, but I'd venture that the ARRL handbook still doesn't mention it (if only because it would be a expensive and herculean task to revise the entire handbook every year). And, folks writing in QST tend not to be in the business, so they're using what they learned in the handbook. For instance, the RFI/EMC page on the arrl web site says: "Original text reprinted from February and March 1992 QST "Lab Notes" columns Copyright © 1992 by the American Radio Relay League, Inc. All rights reserved." "Or, you can make a common-mode choke by wrapping 10 to 20 turns of the antenna feed line or CATV cable through a ferrite toroid. Follow the same procedure with the ac line. Use #75 (also known as "J"), #73 or #77 material if the interference is mainly from signals below 10 MHz. Use #43 ferrite material for the higher bands or low VHF." "To make a ferrite common-mode choke, wrap 5-10 turns of a conductor onto an FT-240-43 ferrite core. (The "240" indicates that the outer diameter of the core is 2.4"; the "43" designates the material. Other materials may be useful, but 43 is a good all-around material.)" (to be fair, they do link to K9YC's writeup) |
Use of type 31 ferrite as coax common mode choke
Dear Jim: Thank you.
I had read an early version of K9YC's work. It was informative to read the latest version. He does a good job. It appears that my question may have had a positive effect and radio-amateurs will consider type 31 for HF. 73, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Jim Lux" wrote in message ... J. Mc Laughlin wrote: Dear Jim: Now I begin to see light. While type 31 must be at least three years old, the world has not yet caught up to its existence. the *amateur* world hasn't caught up.. I haven't looked, but I'd venture that the ARRL handbook still doesn't mention it (if only because it would be a expensive and herculean task to revise the entire handbook every year). And, folks writing in QST tend not to be in the business, so they're using what they learned in the handbook. For instance, the RFI/EMC page on the arrl web site says: "Original text reprinted from February and March 1992 QST "Lab Notes" columns Copyright © 1992 by the American Radio Relay League, Inc. All rights reserved." "Or, you can make a common-mode choke by wrapping 10 to 20 turns of the antenna feed line or CATV cable through a ferrite toroid. Follow the same procedure with the ac line. Use #75 (also known as "J"), #73 or #77 material if the interference is mainly from signals below 10 MHz. Use #43 ferrite material for the higher bands or low VHF." "To make a ferrite common-mode choke, wrap 5-10 turns of a conductor onto an FT-240-43 ferrite core. (The "240" indicates that the outer diameter of the core is 2.4"; the "43" designates the material. Other materials may be useful, but 43 is a good all-around material.)" (to be fair, they do link to K9YC's writeup) |
Use of type 31 ferrite as coax common mode choke
J. Mc Laughlin wrote:
I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in: http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has roughly the same or a little higher total complex permeability than 73 over most of the lower HF range and same or higher than 43 on up to 100 MHz. So it should be a good ferrite to use for very wide band applications. However, Table 1 shows that it's available in large parts only. Type 43 is very widely available in a wide variety of sizes, so you might have a lot more luck getting cores of the sizes you need in type 43. Roy Lewallen, W7EL |
Use of type 31 ferrite as coax common mode choke
J. Mc Laughlin wrote:
P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. You might try Amidon (https://www.amidoncorp.com/) or the Wire Man (http://thewireman.com/baluns.html#901). I don't think I've bought anything from Amidon since Bill Amidon sold it, but see their brand on small quantities of cores at the local electronics shop. Press Jones, the Wire Man, is great to do business with. Roy Lewallen, W7EL |
Use of type 31 ferrite as coax common mode choke
Roy Lewallen wrote:
A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has roughly the same or a little higher total complex permeability than 73 over most of the lower HF range and same or higher than 43 on up to 100 MHz. So it should be a good ferrite to use for very wide band applications. However, Table 1 shows that it's available in large parts only. Type 43 is very widely available in a wide variety of sizes, so you might have a lot more luck getting cores of the sizes you need in type 43. Roy Lewallen, W7EL Amidon do stock some type 31 products, including FT-240-31 toroids and the large beads for RG213, but they aren't listed on the website. Part numbering is the same as normal, so simply substitute a "31" in the part number you wish to order, and then call 1-800-898-1883. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Use of type 31 ferrite as coax common mode choke
"J. Mc Laughlin" wrote in
: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Mac, Whilst playing around with models of a Guanella balun, I did compare #31 sleeves with Walt's design using #73 sleeves over the range 1 - 30MHz. My model of Walt's balun is at http://www.vk1od.net/balun/W2DU/index.htm .. I obtained different results to Walt's measurements, but I think that is because Walt's measurements were affected by stray capacitance that was worse than would apply to that type of balun in service. I also modelled some Fair-rite 2631480002 sleeves and found a slightly longer choke (12 cores at 25.4mm ea) was needed to achieve about the same choking impedance up to about 12MHz, above which the #31 choke had higher impedance than the #73 one. Whilst I modelled these sleeves because they suited the application, I have not seen anyone selling them in small quantities. Owen |
Use of type 31 ferrite as coax common mode choke
Owen Duffy wrote:
Whilst playing around with models of a Guanella balun, I did compare #31 sleeves with Walt's design using #73 sleeves over the range 1 - 30MHz. Owen, have you done any experiments with 'K' material? I have the Amidon AB240-250 Kit but haven't done anything with it. -- 73, Cecil http://www.w5dxp.com |
Use of type 31 ferrite as coax common mode choke
On Apr 21, 10:21*am, "J. Mc Laughlin" wrote:
I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. *That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. *See Figure 26 in:http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? *It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. *This is a receiving application with a long run of coax. 73, * *Mac * N8TT P.S. *I will also appreciate ideas about places to purchase ferrite in addition to Mouser. -- J. McLaughlin; *Michigan, USA Home: I think the type 31 is entended for use on things like power cords and computer cables to prevent unwanted radiation/pickup of RF. Im not sure how well it would meet your requirements but I suspect it may be OK in a receive only situation. I have tried using some unknown types of cores removed from various computer cables for a balun and the vinyl tape holding them to the coax got very soft when they heated up. Perhaps some experimentation using these cores is in order. Jimmie |
Use of type 31 ferrite as coax common mode choke
On Apr 22, 9:47*am, JIMMIE wrote:
On Apr 21, 10:21*am, "J. Mc Laughlin" wrote: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. *That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. *See Figure 26 in:http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? *It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. *This is a receiving application with a long run of coax. 73, * *Mac * N8TT P.S. *I will also appreciate ideas about places to purchase ferrite in addition to Mouser. -- J. McLaughlin; *Michigan, USA Home: I think the type 31 is entended for use on things like power cords and computer cables to prevent unwanted radiation/pickup *of RF. Im not sure how well it would meet your requirements but I suspect it may be OK in a receive only situation. I have tried using some unknown types of cores removed from various computer cables for a balun and the vinyl tape holding them to the coax got very soft when they heated up. Perhaps some experimentation using these cores is in order. Jimmie- Hide quoted text - - Show quoted text - Apparently this testing has already been done. Just google "type 31 ferrite" for results. Jimmie |
Use of type 31 ferrite as coax common mode choke
Roy Lewallen wrote:
J. Mc Laughlin wrote: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in: http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has roughly the same or a little higher total complex permeability than 73 over most of the lower HF range and same or higher than 43 on up to 100 MHz. So it should be a good ferrite to use for very wide band applications. However, Table 1 shows that it's available in large parts only. Type 43 is very widely available in a wide variety of sizes, so you might have a lot more luck getting cores of the sizes you need in type 43. Large, in this context, isn't all that big. You can't get it in tiny ferrite beads to slip over a AWG30 wire. You can get it in 0.485" OD 0.5" long beads with a 0.2" hole in the middle.... $0.42 each from Mouser. Similar snap on cases too.. Small, for Fair-rite, means things like those little 1/4" diameter multi hole cores for making wound EMI filters, or chip components. I buy it in 2.4" toroids so I can put multiple turns of coax on. |
Use of type 31 ferrite as coax common mode choke
Owen Duffy wrote:
"J. Mc Laughlin" wrote in : I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Mac, Whilst playing around with models of a Guanella balun, I did compare #31 sleeves with Walt's design using #73 sleeves over the range 1 - 30MHz. My model of Walt's balun is at http://www.vk1od.net/balun/W2DU/index.htm . I obtained different results to Walt's measurements, but I think that is because Walt's measurements were affected by stray capacitance that was worse than would apply to that type of balun in service. I also modelled some Fair-rite 2631480002 sleeves and found a slightly longer choke (12 cores at 25.4mm ea) was needed to achieve about the same choking impedance up to about 12MHz, above which the #31 choke had higher impedance than the #73 one. Whilst I modelled these sleeves because they suited the application, I have not seen anyone selling them in small quantities. Mouser has them.. Don't know if they ship in VK land or not. Shipping of what is basically iron bars is going to be punitive. FairRite has distribution there (Specialised Conductives in Victoria), but perhaps not retail. But, since one typically isn't looking to buy just one, but dozens, this might not be a problem. One should be careful about modeling these things.. that gets you close, but parasitics are a real bugabear. K9YC's paper has actual measurements on actual chokes made with a variety of cores (which are decidedly non-trivial to make..) Snelling's book is the tome of choice, if you can find it... |
Use of type 31 ferrite as coax common mode choke
JIMMIE wrote:
On Apr 21, 10:21 am, "J. Mc Laughlin" wrote: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in:http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. -- J. McLaughlin; Michigan, USA Home: I think the type 31 is entended for use on things like power cords and computer cables to prevent unwanted radiation/pickup of RF. Im not sure how well it would meet your requirements but I suspect it may be OK in a receive only situation. I have tried using some unknown types of cores removed from various computer cables for a balun and the vinyl tape holding them to the coax got very soft when they heated up. Perhaps some experimentation using these cores is in order. Jimmie #31 is specifically made for our kind of application (transmitting).. it has a higher temperature rating than the other popular materials. The key on managing dissipation is making sure you have enough impedance so that the current is small. It's a long way from the miscellaneous stuff used for RFI on power cords and keyboards.. |
Use of type 31 ferrite as coax common mode choke
Jim Lux wrote:
I buy it in 2.4" toroids so I can put multiple turns of coax on. Jim, have you or anyone else you know of taken a look at 'K' material? -- 73, Cecil http://www.w5dxp.com |
Use of type 31 ferrite as coax common mode choke
The following is a copy of my message posted earlier to the general
group, but I had wanted to preply directly to this topic as it's very pertinent to the discussion of ferrites, so here is the message again (sorry if you see this twice). Greetings All, Saw the posts about Mix 31 ferrites, which I use on my mobile installations with good results, using a HiQ 5/160 antenna and Icom IC7000. If anyone is interested, I recently posted on my web site a document the describes the installation of ferrites for HF installations: : www.repdesign.us , (go to the "Downloads" page (left side of screen towards the bottom), and go to the third group to download or simply open to read the PDF document). This is based on what has worked well for me, information from Fair Rite's web site, and ideas from various past posings. Also listed is a partial list of suppliers - as always check the prices as they can vary a lot! Check it out and let me know (direct email) if you have any other suggestions and if you find this useful, as this is meant to be a "continous improvement" document. I also plan to write additional guidelines as time permits. 73, Dick Post, N7EMW www.repdesign.us On Apr 21, 10:21*am, "J. Mc Laughlin" wrote: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. *That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. *See Figure 26 in:http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? *It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. *This is a receiving application with a long run of coax. 73, * *Mac * N8TT P.S. *I will also appreciate ideas about places to purchase ferrite in addition to Mouser. -- J. McLaughlin; *Michigan, USA Home: |
Use of type 31 ferrite as coax common mode choke
Jim Lux wrote in
: Mouser has them.. Don't know if they ship in VK land or not. Yes, but shipping anything from them and some other big suppliers is prohibitive. Shipping of what is basically iron bars is going to be punitive. FairRite has distribution there (Specialised Conductives in Victoria), but perhaps not retail. But, since one typically isn't looking to buy just one, but dozens, this might not be a problem. For some reason, magnetics ex USA through Aussie distributors / retailers are outrageously expensive. Typically on Ebay one can buy 10 cores ex USA for the price of one from a Aussie retailer. One should be careful about modeling these things.. that gets you close, but parasitics are a real bugabear. K9YC's paper has actual Yes, agreed. I have made measurements of a number of choke configurations, albeit only with a TAPR VNA (hate the software), and calibrated my models to the measured values. It is certainly a balancing act to put enough turns on a toroid to get high Z, but few enough turns that Z hasn't gone seriously south at the top end of the desired range. Predicting magnetics behaviour is a bit of a black art, but models help to guide one to a better understanding of behaviour. It is little wonder than balun specifications, where they are given, bear little relation to the intended application. Owen |
Use of type 31 ferrite as coax common mode choke
Dear Roy: The use of small and large in this context is not clear. So far,
I have found the sizes of type 31 to be about the right size. On the other hand, some of the 7X types seem only to be available in sizes that are too small. Your point that the type, and its performance, is only part of the issue. One must also have parts that fit. Thanks, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Roy Lewallen" wrote in message news:JZSdnd4om7o7-5DVnZ2dnUVZ_jCdnZ2d@easystreetonline... J. Mc Laughlin wrote: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in: http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has roughly the same or a little higher total complex permeability than 73 over most of the lower HF range and same or higher than 43 on up to 100 MHz. So it should be a good ferrite to use for very wide band applications. However, Table 1 shows that it's available in large parts only. Type 43 is very widely available in a wide variety of sizes, so you might have a lot more luck getting cores of the sizes you need in type 43. Roy Lewallen, W7EL |
Use of type 31 ferrite as coax common mode choke
Dear Ian (also my father's name): Thank you for your note. It is a
mystery to me why those who sell via the Internet do not work hard at keeping their sites up-to-date. 73, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Ian White GM3SEK" wrote in message ... Roy Lewallen wrote: A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has roughly the same or a little higher total complex permeability than 73 over most of the lower HF range and same or higher than 43 on up to 100 MHz. So it should be a good ferrite to use for very wide band applications. However, Table 1 shows that it's available in large parts only. Type 43 is very widely available in a wide variety of sizes, so you might have a lot more luck getting cores of the sizes you need in type 43. Roy Lewallen, W7EL Amidon do stock some type 31 products, including FT-240-31 toroids and the large beads for RG213, but they aren't listed on the website. Part numbering is the same as normal, so simply substitute a "31" in the part number you wish to order, and then call 1-800-898-1883. -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Use of type 31 ferrite as coax common mode choke
Dear Jim: Right. Small and large have somewhat unexpected uses by
Fair-Rite. Thanks for the useful observation, 73 Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Jim Lux" wrote in message ... Roy Lewallen wrote: J. Mc Laughlin wrote: I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Recommendations for HF choking ferrites have centered on the 70 series with type 43 being favorably recommended for the upper portion of HF and VHF. However, Fair-Rite seems to be recommending type 31 for HF. See Figure 26 in: http://www.fair-rite.com/newfair/pdf/CUP%20Paper.pdf Am I missing something? It seems to me that for the purpose of choking common mode current (on the outside of the outer conductor of coax) from 3 to 25 MHz one should prefer the use of type 31. This is a receiving application with a long run of coax. 73, Mac N8TT P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has roughly the same or a little higher total complex permeability than 73 over most of the lower HF range and same or higher than 43 on up to 100 MHz. So it should be a good ferrite to use for very wide band applications. However, Table 1 shows that it's available in large parts only. Type 43 is very widely available in a wide variety of sizes, so you might have a lot more luck getting cores of the sizes you need in type 43. Large, in this context, isn't all that big. You can't get it in tiny ferrite beads to slip over a AWG30 wire. You can get it in 0.485" OD 0.5" long beads with a 0.2" hole in the middle.... $0.42 each from Mouser. Similar snap on cases too.. Small, for Fair-rite, means things like those little 1/4" diameter multi hole cores for making wound EMI filters, or chip components. I buy it in 2.4" toroids so I can put multiple turns of coax on. |
Use of type 31 ferrite as coax common mode choke
Dear Roy: I think that I looked at those sites, however I will take
another look. 73, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Roy Lewallen" wrote in message news:QqqdndKq2bKv9ZDVnZ2dnUVZ_gOdnZ2d@easystreeton line... J. Mc Laughlin wrote: P.S. I will also appreciate ideas about places to purchase ferrite in addition to Mouser. You might try Amidon (https://www.amidoncorp.com/) or the Wire Man (http://thewireman.com/baluns.html#901). I don't think I've bought anything from Amidon since Bill Amidon sold it, but see their brand on small quantities of cores at the local electronics shop. Press Jones, the Wire Man, is great to do business with. Roy Lewallen, W7EL |
Use of type 31 ferrite as coax common mode choke
Dear Owen: Stray capacitance due to more than one source has a big effect.
Your getting similar results with a few more 31 types than 73 types is certainly above the noise level and reinforces the utility of 31. Thanks. 73, Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Owen Duffy" wrote in message ... "J. Mc Laughlin" wrote in : I looked through saved messages and the only reference to type 31 ferrite (Fair-Rite) was in March of 2005. That reference had to do with ignition wires. Mac, Whilst playing around with models of a Guanella balun, I did compare #31 sleeves with Walt's design using #73 sleeves over the range 1 - 30MHz. My model of Walt's balun is at http://www.vk1od.net/balun/W2DU/index.htm . I obtained different results to Walt's measurements, but I think that is because Walt's measurements were affected by stray capacitance that was worse than would apply to that type of balun in service. I also modelled some Fair-rite 2631480002 sleeves and found a slightly longer choke (12 cores at 25.4mm ea) was needed to achieve about the same choking impedance up to about 12MHz, above which the #31 choke had higher impedance than the #73 one. Whilst I modelled these sleeves because they suited the application, I have not seen anyone selling them in small quantities. Owen |
Amidon Use of type 31 ferrite as coax common mode choke
J. Mc Laughlin wrote:
Dear Ian (also my father's name): Thank you for your note. It is a mystery to me why those who sell via the Internet do not work hard at keeping their sites up-to-date. 73, Mac N8TT Amidon is sort of on-again/off-again when it comes to supporting the retail ham market. Sometimes they are pretty good, but other times they're just terrible. Might have something to do with changes in ownership and management over the years, or just whether they get busy with bread and butter commerical customers. They've also used a wide variety of suppliers over the years. And the whole Amidon, Amidon Associates, Applied Magnetics, BTC Power Electronics, Flat Transformer Technology, thing... It's been a long time since Bill Amidon ran it from his garage in North Hollywood providing retail distribution for Fair-Rite and Micrometals products. |
Use of type 31 ferrite as coax common mode choke
"J. Mc Laughlin" wrote in
: Dear Ian (also my father's name): Thank you for your note. It is a mystery to me why those who sell via the Internet do not work hard at keeping their sites up-to-date. 73, Mac N8TT Mac, If you have your heart set on #31 mix, this option isn't a good one... but if you can use #73 or #43, you will regularly see sleeves in various sizes and materials on Ebay. Many have Fair-rite numbers so you can check to see if they suit. Some advertisers state that the cores are Fair-rite cores, if they know that, they should know the part numbers though they don't always state them in the descriptions. I have bought ferrites from one of the suppliers, the goods seem to comply with the part number descriptions (dimensions, mu) and their service to Australia was quick and cheap. In this part of the world, product from Asia is available economically... but we have to characterise them and long term product availability is a bit of an issue. Owen |
Use of type 31 ferrite as coax common mode choke
Dear Owen: Always good to receive your insight.
Were I to deal with Ebay, I would have a dedicated computer and ISP just for that purpose. I am much too much a belt and suspenders person to wish to avail myself of their "bargains." I leave that to those who are younger. You have reinforced my expectation that from VK land it simply might be a necessity to deal with Ebay and to measure materials received from any distant source. As an extension, a new field proposed at our university is that of a specialized engineer who is able to make the importation of parts from all over the world work. This has become a real field. It is much worse than the three metric systems that existed at the beginning of WW2 (American, Canadian, and English) such that bolts might only engage a few threads before seizing. Your skepticism about type 31 causes me to revisit my assumptions. As always, 73 Mac N8TT -- J. McLaughlin; Michigan, USA Home: "Owen Duffy" wrote in message ... "J. Mc Laughlin" wrote in : Dear Ian (also my father's name): Thank you for your note. It is a mystery to me why those who sell via the Internet do not work hard at keeping their sites up-to-date. 73, Mac N8TT Mac, If you have your heart set on #31 mix, this option isn't a good one... but if you can use #73 or #43, you will regularly see sleeves in various sizes and materials on Ebay. Many have Fair-rite numbers so you can check to see if they suit. Some advertisers state that the cores are Fair-rite cores, if they know that, they should know the part numbers though they don't always state them in the descriptions. I have bought ferrites from one of the suppliers, the goods seem to comply with the part number descriptions (dimensions, mu) and their service to Australia was quick and cheap. In this part of the world, product from Asia is available economically... but we have to characterise them and long term product availability is a bit of an issue. Owen |
| All times are GMT +1. The time now is 12:46 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com