Re: [Elecraft] OT: J and -31 mix toroids
On Tue, 7 Apr 2009 05:37:40 -0700 (PDT), Julius Fazekas n2wn wrote: Jim, ask for a quote from whom? WX0B or Fair-Rite? For small and medium quantities, WX0B. For large quantity ($500-$1,000 min order, buy only in box quantities), Fair-Rite or other distributions listed on their website and in Appendix One of my tutorial. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
I think Allied or some of the others in your article will sell in smaller quantities. Make sure you know what you are ordering. Maybe WX0B buys enough to get a better discount. CC Packet Cluster W0MU-1 W0MU.NET or 67.40.148.194 A slip of the foot you may soon recover, but a slip of the tongue you may never get over. Ben Franklin -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Jim Brown Sent: Wednesday, April 08, 2009 9:50 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] OT: J and -31 mix toroids On Tue, 7 Apr 2009 05:37:40 -0700 (PDT), Julius Fazekas n2wn wrote: Jim, ask for a quote from whom? WX0B or Fair-Rite? For small and medium quantities, WX0B. For large quantity ($500-$1,000 min order, buy only in box quantities), Fair-Rite or other distributions listed on their website and in Appendix One of my tutorial. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
On Tue, 7 Apr 2009 09:23:15 -0700 (PDT), Julius Fazekas n2wn wrote: I see it's a pretty common question once I found the part number... I don't get it. I went to a LOT of trouble to write that tutorial, then post a link to it in response to questions like this, tell people where to look, and still questions like this. The Fair-Rite part numbers are listed with graphs of the performance of these parts in the tutorial where they are discussed in the text, and REPEATED in Appendix One, with detailed advice about where to buy them and how to buy them. Everything you need to know to wind chokes for the bands you want to operate is in the Choke Cookbook. 73, Jim Brown K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
Mike and all, Loadstone quoted $5.4506 each for quantities of 1 to 249 pieces. They do have a minimum order of $50. Very nice on the phone. I'm ordering for our Tennessee Contest Group, so we will exceed the minimum by a little bit ;o) This should kill the last of the garbage on my 160M antenna. Cheers, Julius Fair-Rite has a quite high minimum order value, several hundred dollars as I recall. OTOH Mouser stocks most of the 31 material you would likely find useful including the 2.4 inch toroids and the monster snap-on. The Fair-Rite web site has all the technical info you will need to cross-reference to the correct part on Mouser. Mouser unit cost is also quite high. I joined forces with a local ham friend and we purchased our mix 31 toroids and the biggest clamp on at Lodestone Pacific http://www.lodestonepacific.com/ You might see if you can get some friends to go in with you and save some money. We purchased in quantities of 20 each and they were quite happy to deal with us, fast and courteous. I don't know if we had requested a smaller quantity if they would be so willing. They are a distributor not a retail house. You have to know exactly what you want so know the Fair-Rite catalog number. The Fair-Rite catalog is on the Lodestone Pacific site. The 2.4 inch toroid is part number 2631803802 The biggest clamp on number is 0431177081, This is a substantial clamp on and is quite useful. It can handle 1 inch cable but is really good for example for passing RG8X through it 7 or so times to create a really high impedance common mode choke at your antenna feed point or elsewhere. For shopping comparison purposes here is what we paid in January of this year: --2.4 inch toroid (mix 31): $5.46 each, quantity 20 --Biggest clamp on (Round Cable Snap-it, mix 31): $9.39 each, quantity 20. Tax was zero and shipping was $7.60 for entire lot. Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) NAQCC 3535 K3-100 #508 / KX1 #1311 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html - Julius Fazekas N2WN Tennessee Contest Group http://www.k4ro.net/tcg/index.html Tennessee QSO Party http://www.tnqp.org/ Elecraft K2/100 #4455 Elecraft K3/100 #366 -- View this message in context: http://n2.nabble.com/OT%3A-J-and--31-mix-toroids-tp2593939p2606222.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
-Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft- boun...@mailman.qth.net] On Behalf Of Jim Brown Sent: Wednesday, April 08, 2009 8:57 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] OT: J and -31 mix toroids On Tue, 7 Apr 2009 09:23:15 -0700 (PDT), Julius Fazekas n2wn wrote: I see it's a pretty common question once I found the part number... I don't get it. I went to a LOT of trouble to write that tutorial, then post a link to it in response to questions like this, tell people where to look, and still questions like this. Well, I for one appreciate the write up! I called and ordered a box of them from one of the distributors and got a great deal! Thanks! Adam - K3ARK __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
Pretty simple Jim, I'm old ;o) I probably have three copies of this tutorial printed in various locations, but never where I need it when I have time to search. On the other hand, I do recall the size and material of the item in question. Usually that's an easy way to search for surplus parts, uber cheap. It doesn't always work. Fair-Rite's number system is not particularly user friendly either. We could discuss spam ;o) Cheers, Julius Julius Fazekas N2WN Tennessee Contest Group http://www.k4ro.net/tcg/index.html Tennessee QSO Party: Sunday, 6 Sept 2009 http://www.tnqp.org/ Elecraft K2/100 #4455 Elecraft K3/100 #366 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
Thanks to all for the replies... Didn't quite get an answer to the -J versus -31, but still useful. Jim, ask for a quote from whom? WX0B or Fair-Rite? Cheers, Julius On Mon, 06 Apr 2009 17:03:50 -0400, Jack Smith wrote: You might wish to experiment with Steward mix 35 or 40 toroids. Mix 35 has a relative permeability of 5000 and mix 40 is 10,000. Fair-Rite's 31 material has a relative permeability of 1500. Relative permeabilility varies with frequency -- it is NOT a constant (unless you use a parallel equivalent circuit). The numbers you are quoting are low frequency values. Steward's 35 and 40 material are MnZn ferrites and will have dimensional resonance in the HF frequency range, with the exact frequency depending on the core dimension. I suspect that dimensional resonance won't be an issue for a current choke at your frequency range, however. Fair-Rite claims the 31 material, although also a MnZn ferrite, does not have dimensional resonance. Fair-Rite has always said that -- they said it to me six years ago when I first convinced them to make #31 toroids! Perhaps they said it because they viewed it as a negative. Or perhaps they wanted to throw off their competitors. :) But our data for multiturn chokes disproves that! Fair-Rite #31 DOES have a mild dimensional resonance in the 2-5 MHz range. That is what gives the pronounced broadening of the impedance curve when you wind enough turns to move the circuit resonance below 5 MHz! That is, the dimensional resonance and the circuit resonance combine to act as very low Q stagger tuned circuits, extending the usefulness of the choke by something on the order of 3/4 octave as compared to materials like #43. That means that a single choke on #31 can cover 160, 80, and 40 effectively, and still be decent on 30M. With fewer turns it can cover 80-20. And so on. Type 43 is a NiZn ferrite and does not have dimensional resonance in the HF frequency band. In general, NiZn ferrites exhibit no measureable dimensional resonance because it occurs at VHF, where it is damped by the loss in the core. To answer Julius's question directly. See my Choke Cookbook for specific recommendations on winding chokes for the HF bands. http://audiosystemsgroup.com/RFI-Ham.pdf BTW -- I just got an email from Jay Terleski, WX0B, telling me that he is now stocking #31 toroids, bought out Fair-Rite's stock (900 pieces), and has more on order. He didn't quote prices. Jay also told me that he is now using #31 material for the high power transmitting chokes that he builds. I suggest that you ask for a quote on at least 20 pieces. As active as you are, you'll put them to good use in a few months! 73, Jim Brown K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html - Julius Fazekas N2WN Tennessee Contest Group http://www.k4ro.net/tcg/index.html Tennessee QSO Party http://www.tnqp.org/ Elecraft K2/100 #4455 Elecraft K3/100 #366 -- View this message in context: http://n2.nabble.com/OT%3A-J-and--31-mix-toroids-tp2593939p2598678.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
Julius wrote: Jim, ask for a quote from whom? WX0B or Fair-Rite? Perhaps http://www.arraysolutions.com/ [http://www.arraysolutions.com/] ? 73, Svend OZ7UV TDC Bredbånd for 0 kr. - Spar 695 kr. Se http://tdc.dk/freemailtilbud/ Denne mail er sendt via Mail på TDC Online - Læs mere om TDC's mailtjeneste på http://mail.tdconline.dk/ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
Hi Svend,
They don't list them, and I suspect the ones they purchased are for their
Balun/Unun products. I'm going to contact Fair Rite directly...
Julius Fazekas
N2WN
Tennessee Contest Group
http://www.k4ro.net/tcg/index.html
Tennessee QSO Party: Sunday, 6 Sept 2009
http://www.tnqp.org/
Elecraft K2/100 #4455
Elecraft K3/100 #366
--- On Tue, 4/7/09, Svend Spanget span...@privat.dk wrote:
From: Svend Spanget span...@privat.dk
Subject: Re: [Elecraft] OT: J and -31 mix toroids
To: Julius Fazekas n2wn phriend...@yahoo.com
Cc: elecraft@mailman.qth.net
Date: Tuesday, April 7, 2009, 9:24 AM
#yiv926258770 pre {
white-space:pre-wrap;word-wrap:break-word;}
Julius wrote:
Jim, ask for a quote from
whom? WX0B or Fair-Rite?
Perhaps http://www.arraysolutions.com/ ?
73, Svend OZ7UV
TDC Bredbånd for 0 kr.
- Spar 695 kr. Se http://tdc.dk/freemailtilbud/
Denne mail er sendt via Mail på TDC Online
- Læs mere om TDC's mailtjeneste på
http://mail.tdconline.dk/
__
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Re: [Elecraft] OT: J and -31 mix toroids
Fair-Rite has a quite high minimum order value, several hundred dollars as I
recall. OTOH Mouser stocks most of the 31 material you would likely find
useful including the 2.4 inch toroids and the monster snap-on. The Fair-Rite
web site has all the technical info you will need to cross-reference to the
correct part on Mouser.
Chuck, AE4CW
Hi Svend,
They don't list them, and I suspect the ones they purchased are for their
Balun/Unun products. I'm going to contact Fair Rite directly...
Julius Fazekas
N2WN
Tennessee Contest Group
http://www.k4ro.net/tcg/index.html
Tennessee QSO Party: Sunday, 6 Sept 2009
http://www.tnqp.org/
Elecraft K2/100 #4455
Elecraft K3/100 #366
--- On Tue, 4/7/09, Svend Spanget span...@privat.dk wrote:
From: Svend Spanget span...@privat.dk
Subject: Re: [Elecraft] OT: J and -31 mix toroids
To: Julius Fazekas n2wn phriend...@yahoo.com
Cc: elecraft@mailman.qth.net
Date: Tuesday, April 7, 2009, 9:24 AM
#yiv926258770 pre {
white-space:pre-wrap;word-wrap:break-word;}
Julius wrote:
Jim, ask for a quote from
whom? WX0B or Fair-Rite?
Perhaps http://www.arraysolutions.com/ ?
73, Svend OZ7UV
TDC Bredbånd for 0 kr.
- Spar 695 kr. Se http://tdc.dk/freemailtilbud/
Denne mail er sendt via Mail på TDC Online
- Læs mere om TDC's mailtjeneste på
http://mail.tdconline.dk/
__
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Please help support this email list: http://www.qsl.net/donate.html
--
View this message in context:
http://n2.nabble.com/OT%3A-J-and--31-mix-toroids-tp2593939p2599394.html
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__
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Re: [Elecraft] OT: J and -31 mix toroids
Hi Chuck,
It really helps if one knows the proper name for an item. In this case, toroid
ain't it ;o) It's considered a bead. Not sure what the difference is, other
than maybe thickness?
The part in question is stocked by Mouser:
http://www.mouser.com/Search/ProductDetail.aspx?qs=P8bU7i9nNAWMk1EJQzshLg%3D%3D
It's reasonably priced too.
Fair Rite was helpful on the phone too.
Array Solutions also stocks the part.
Thanks for all the help and the space. I see it's a pretty common question once
I found the part number...
Happy building all!
Julius
Fair-Rite has a quite high minimum order value, several hundred dollars as I
recall. OTOH Mouser stocks most of the 31 material you would likely find
useful including the 2.4 inch toroids and the monster snap-on. The Fair-Rite
web site has all the technical info you will need to cross-reference to the
correct part on Mouser.
Chuck, AE4CW
Hi Svend,
They don't list them, and I suspect the ones they purchased are for their
Balun/Unun products. I'm going to contact Fair Rite directly...
Julius Fazekas
N2WN
Tennessee Contest Group
http://www.k4ro.net/tcg/index.html
Tennessee QSO Party: Sunday, 6 Sept 2009
http://www.tnqp.org/
Elecraft K2/100 #4455
Elecraft K3/100 #366
--- On Tue, 4/7/09, Svend Spanget span...@privat.dk wrote:
From: Svend Spanget span...@privat.dk
Subject: Re: [Elecraft] OT: J and -31 mix toroids
To: Julius Fazekas n2wn phriend...@yahoo.com
Cc: elecraft@mailman.qth.net
Date: Tuesday, April 7, 2009, 9:24 AM
#yiv926258770 pre {
white-space:pre-wrap;word-wrap:break-word;}
Julius wrote:
Jim, ask for a quote from
whom? WX0B or Fair-Rite?
Perhaps http://www.arraysolutions.com/ ?
73, Svend OZ7UV
TDC Bredbånd for 0 kr.
- Spar 695 kr. Se http://tdc.dk/freemailtilbud/
Denne mail er sendt via Mail på TDC Online
- Læs mere om TDC's mailtjeneste på
http://mail.tdconline.dk/
__
Elecraft mailing list
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Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
-
Julius Fazekas
N2WN
Tennessee Contest Group
http://www.k4ro.net/tcg/index.html
Tennessee QSO Party
http://www.tnqp.org/
Elecraft K2/100 #4455
Elecraft K3/100 #366
--
View this message in context:
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[Elecraft] OT: J and -31 mix toroids
I know there are several folks here who could answer this questions. I'm looking to improve my current chokes for my 160 and 80 Tx antennas. I was planning on going with -43 material, but after reading thought -J and/or -31 mixes might be a better solution. The 31 mix seems a bit more difficult to find cheep. J material is a bit more common on the excess sites. Would I notice a difference? Currently, the 160 antenna is a Tee Vertical. 80 is a dipole, but looking at adding a Delta Loop now that I cleared out some brush... Thanks in advance... 73, Julius - Julius Fazekas N2WN Tennessee Contest Group http://www.k4ro.net/tcg/index.html Tennessee QSO Party http://www.tnqp.org/ Elecraft K2/100 #4455 Elecraft K3/100 #366 -- View this message in context: http://n2.nabble.com/OT%3A-J-and--31-mix-toroids-tp2593939p2593939.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
You might wish to experiment with Steward mix 35 or 40 toroids. Mix 35 has a relative permeability of 5000 and mix 40 is 10,000. Fair-Rite's 31 material has a relative permeability of 1500. Digikey carries several sizes of toroid cores in mix 35 and 40 at moderate price. Search DigiKey's web site for 35T or 40T to see what they have available. For example, a 1 inch OD core is $1.19 in single lot quantities. Smaller cores, 0.54 inch OD, are 23 cents each in single lot. Steward's 35 and 40 material are MnZn ferrites and will have dimensional resonance in the HF frequency range, with the exact frequency depending on the core dimension. I suspect that dimensional resonance won't be an issue for a current choke at your frequency range, however. Fair-Rite claims the 31 material, although also a MnZn ferrite, does not have dimensional resonance. Type 43 is a NiZn ferrite and does not have dimensional resonance in the HF frequency band. Jack K8ZOA Julius Fazekas n2wn wrote: I know there are several folks here who could answer this questions. I'm looking to improve my current chokes for my 160 and 80 Tx antennas. I was planning on going with -43 material, but after reading thought -J and/or -31 mixes might be a better solution. The 31 mix seems a bit more difficult to find cheep. J material is a bit more common on the excess sites. Would I notice a difference? Currently, the 160 antenna is a Tee Vertical. 80 is a dipole, but looking at adding a Delta Loop now that I cleared out some brush... Thanks in advance... 73, Julius - Julius Fazekas N2WN Tennessee Contest Group http://www.k4ro.net/tcg/index.html Tennessee QSO Party http://www.tnqp.org/ Elecraft K2/100 #4455 Elecraft K3/100 #366 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
I should also mention that Mouser carries some Fair-Rite mix 31 cores. They are in the catalog at Fair-Rite -- http://www.mouser.com/catalog/637/917.pdf is the current catalog page. Jack K8ZOA Julius Fazekas n2wn wrote: I know there are several folks here who could answer this questions. I'm looking to improve my current chokes for my 160 and 80 Tx antennas. I was planning on going with -43 material, but after reading thought -J and/or -31 mixes might be a better solution. The 31 mix seems a bit more difficult to find cheep. J material is a bit more common on the excess sites. Would I notice a difference? Currently, the 160 antenna is a Tee Vertical. 80 is a dipole, but looking at adding a Delta Loop now that I cleared out some brush... Thanks in advance... 73, Julius - Julius Fazekas N2WN Tennessee Contest Group http://www.k4ro.net/tcg/index.html Tennessee QSO Party http://www.tnqp.org/ Elecraft K2/100 #4455 Elecraft K3/100 #366 __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
Subject: Re: [Elecraft] OT: J and -31 mix toroids You might wish to experiment with Steward mix 35 or 40 toroids. Mix 35 has a relative permeability of 5000 and mix 40 is 10,000. Fair-Rite's 31 material has a relative permeability of 1500. Digikey carries several sizes of toroid cores in mix 35 and 40 at moderate price. Search DigiKey's web site for 35T or 40T to see what they have available. For example, a 1 inch OD core is $1.19 in single lot quantities. Smaller cores, 0.54 inch OD, are 23 cents each in single lot. Steward's 35 and 40 material are MnZn ferrites and will have dimensional resonance in the HF frequency range, with the exact frequency depending on the core dimension. I suspect that dimensional resonance won't be an issue for a current choke at your frequency range, however. Fair-Rite claims the 31 material, although also a MnZn ferrite, does not have dimensional resonance. Type 43 is a NiZn ferrite and does not have dimensional resonance in the HF frequency band. Jack K8ZOA __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] OT: J and -31 mix toroids
On Mon, 06 Apr 2009 17:03:50 -0400, Jack Smith wrote: You might wish to experiment with Steward mix 35 or 40 toroids. Mix 35 has a relative permeability of 5000 and mix 40 is 10,000. Fair-Rite's 31 material has a relative permeability of 1500. Relative permeabilility varies with frequency -- it is NOT a constant (unless you use a parallel equivalent circuit). The numbers you are quoting are low frequency values. Steward's 35 and 40 material are MnZn ferrites and will have dimensional resonance in the HF frequency range, with the exact frequency depending on the core dimension. I suspect that dimensional resonance won't be an issue for a current choke at your frequency range, however. Fair-Rite claims the 31 material, although also a MnZn ferrite, does not have dimensional resonance. Fair-Rite has always said that -- they said it to me six years ago when I first convinced them to make #31 toroids! Perhaps they said it because they viewed it as a negative. Or perhaps they wanted to throw off their competitors. :) But our data for multiturn chokes disproves that! Fair-Rite #31 DOES have a mild dimensional resonance in the 2-5 MHz range. That is what gives the pronounced broadening of the impedance curve when you wind enough turns to move the circuit resonance below 5 MHz! That is, the dimensional resonance and the circuit resonance combine to act as very low Q stagger tuned circuits, extending the usefulness of the choke by something on the order of 3/4 octave as compared to materials like #43. That means that a single choke on #31 can cover 160, 80, and 40 effectively, and still be decent on 30M. With fewer turns it can cover 80-20. And so on. Type 43 is a NiZn ferrite and does not have dimensional resonance in the HF frequency band. In general, NiZn ferrites exhibit no measureable dimensional resonance because it occurs at VHF, where it is damped by the loss in the core. To answer Julius's question directly. See my Choke Cookbook for specific recommendations on winding chokes for the HF bands. http://audiosystemsgroup.com/RFI-Ham.pdf BTW -- I just got an email from Jay Terleski, WX0B, telling me that he is now stocking #31 toroids, bought out Fair-Rite's stock (900 pieces), and has more on order. He didn't quote prices. Jay also told me that he is now using #31 material for the high power transmitting chokes that he builds. I suggest that you ask for a quote on at least 20 pieces. As active as you are, you'll put them to good use in a few months! 73, Jim Brown K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
