|
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 |
| All times are GMT +1. The time now is 10:44 AM. |
Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
RadioBanter.com