#2 powdered iron at mu of 10 is the lowest mu of the powdered iron types listed with a frequency range that covers 160 meters (in some lists #2 is 2-30). You can rest assured Jerry Sevick had the list below. In his 160 meter comparison with #2 material, he tested 1,3,15 and 26. Number 6 really doesn't work under 10 MHz, as specified in other lists. It's a "replaced" mix that has had problems. Here's a composite list of powdered iron materials from various incomplete sources.
0 Mix (Tan) 100-300 MHz u=1 1 Mix (Blue) 0.5-5 Mhz u=20 *2 Mix* (Red) 1-30 MHz, high volume resist. u=10 [Alt list 2-30 Mhz] 3 Mix (Gray) .05-.5 MHz, u=35 *6 Mix* (Yellow) 1-50 MHz, similar to mix #2. u=8 [alt list 10-50 MHz, alt list use #8] 7 Mix 3-35 MHz, u=9 small cores only *8 Mix *(Yellow / Red) 1-50 MHz, replaces 6 mix. u=35 10 Mix 30-100 MHz, u=6 12 Mix 50-200 MHz, u=4 15 Mix 0.1-2 MHz, u=25 *17 Mix* (Blue/Yellow) 50-200 MHz, good Q. u=3 [alt list u=4] *18 Mix* (Green/Red) u=55, Low Core Loss, Similar to 8 Mix *26 Mix* (Yellow/White) DC-800 KHz, great 60 Hz. EMI range. Line 'em up on speakers / AC wires u=75 *40 Mix* (Green/Yellow) Power conversion similar to mix 26 *52 Mix* (Green/Blue) DC-1 MHz, high perm. u=75 73, Guy. On Thu, Dec 15, 2011 at 10:50 PM, ZR <[email protected]> wrote: > > ----- Original Message ----- From: "Guy Olinger K2AV" < > [email protected]> > To: <[email protected]> > Cc: <[email protected]>; "Martin" <[email protected]> > Sent: Thursday, December 15, 2011 10:05 PM > > Subject: Re: Topband: T-200 vs. T-300 > > > Hi Rick, >> >> No magic. Just the right stuff, for the FCP, anyway. >> >> To your particulars, when Jerry Sevick measured various ferrites, he >> measured the lowest loss at mu=40. This was very low, as was the #2 >> powdered iron at mu=10, the lowest of the powdered iron formulas. >> > > Since when is a 2 mix the lowest mu? It is ideal for QRO and HF since 6 > and 7 mix arent made in QRO sizes and arent suitable at 160 anyway. > > Carl > KM1H > > > > > So use > >> of ferrites introduces a significantly reduced number of turns, with a >> much >> more coarse granularity of possible inductive values, that has to be >> worked >> out to use with the FCP, AND the behavior of the mu=40 core under highly >> reactive loads is not spec'd by the manufacturer. The ferrite will have >> far >> less radiating surface if it does heat up under extreme reactive load, AND >> the length of the parallel bifilar wires may not be enough to cover 160 >> with the needed behavior in this app. >> >> But my admonition about no ferrites has more to do with my knowing that >> people have misc T240 and T200 form factor ferrites of ALL KINDS laying >> around, and want to use the one they just found down in the junk box, >> which >> does NOT have the material # or mu marked on it anywhere. And these >> requests seem to pop up just before a contest, when most hope of getting >> the correct stuff before contest has gone by the wayside. You will note >> that I have pounded in Amidon T300A-2 #2 powdered iron toroid or strict >> equivalent, over and over again. And I get back "please, please, please >> tell me that I can use my junkbox ferrite toroid". But don't hold your >> breath. In over four years of working with non-resonant antenna solutions >> on 160, **NONE** of the ferrites we tried to use made it. We burnt or >> cracked ALL of them at QRO. ALL of them. Really. Ferrite demolition >> derby. >> >> I have a new collection of #31 ferrite stuff, but I use those in low band >> RFI suppression, not transformers. So I'm NOT going to tell anyone it's >> OK >> to use a ferrite toroid for feeding an FCP. >> >> Beyond that, what is NOT in doubt is that the #2 powdered iron choice >> works >> and works well. The installations where I have been able to run QRO brick >> on key and quick go check toroid temp have all been stone cold. Anyone >> has >> contrary experience please let us know ASAP. We will certainly want to >> investigate and determine why in one place and why not in another. >> >> As to why he made his #2 powdered iron choice, Jerry Sevick W2FMI, covers >> this convincingly in his book, pages 58-63, which I will NOT try to >> reproduce on the reflector, as even if I did, I can't pass along the >> essential graphs, photos and diagrams. ("Understanding, Building, and >> Using Baluns and Ununs -- Theory and Practical Designs for the >> Experimenter", Jerry Sevick W2FMI, Copyright 2003, CQ Communications, >> Inc., >> Hicksville, New York) >> >> I have found, over the time that I have been working on top-band issues, >> that dropping back after blowing something up and consulting W2FMI or his >> material has been most valuable. >> >> Alas, Jerry is a silent key, and I can no longer phone him to further >> expound upon his choices. He particularly chose the large #2 powdered >> iron >> cores for applications with a lot of stress on the core, particularly 160 >> meters. Some key quotes: >> >> "Because my simple loss measurements indicated that the higher >> permeability >> powdered-irons had more loss than the No. 2 material, I decided to design >> a >> 4:1 Ruthroff Balun using this material--but with a larger core and more >> turns than the McCoy Balun. Although McCoy's design has enjoyed >> considerable success over the years, I felt that a larger inductive >> reactance was desirable in order to assure better performance on the lower >> frequency bands (particularly 160 meters). [Ibid p.59] >> >> "I knew ... that loss with ferrite materials was related to the voltage >> drop along the length of the [bifilar winding] and to the ... >> permeability. >> Permeabilities of 40 (No. 67 Ferrite) exhibited the lowest loss. ... >> powdered iron #2 material with a permeability of 10 also showed the very >> same low loss. Because powdered-iron material has been known to be more >> rugged and linear than ferrite material, this suggested that other >> powdered-irons ... should be investigated. ... However all four materials >> showed a definite lower input impedance than #2 material, ..." [Ibid >> p.59] >> >> Sevick had access to all of the ferrites, but did not choose any of them >> for his monster hang-on-the-back-of-the-tuner 4:1 Balun, especially >> intended to deal with wild voltages, very reactive loads, etc, and handle >> them as well on 160 as 80-10. Instead Sevick chose the T400A-2 and #2 >> powdered iron to lay out there as his personal method. So we've done the >> same. And everywhere we've used teflon-sleeved #14 double polyimide on >> the >> #2 powdered iron cores, bad stuff has just quit happening, they work, and >> they run stone cold. >> >> At various scattered places in the book Sevick talks about all the issues >> that come to bear on designing an isolation transformer on 160 meters. I >> may not be able to develop a federal level proof case satisfactory so >> some, >> but I am sticking with Mr. Sevick. His guidance has always panned out and >> explained what was ailing. He did his high-stress 160 meter windings on >> large #2 powdered iron toroids after research. So are we. We have the >> hard-won results that prove out Sevick's and our choices. >> >> 73, Guy. >> >> On Thu, Dec 15, 2011 at 2:58 PM, Rick Karlquist <[email protected] >> >wrote: >> >> Guy Olinger K2AV wrote: >>> >>> > Martin has the right instincts, says it feels fishy for this. But it's >>> > worse than he thinks. And don't even consider using ferrites. >>> > >>> > The T300A-2 core and 20 bifilar turns were SPECIFICALLY chosen to > >>> produce >>> > a >>> > residual inductance value in the right order of magnitude to cancel a >>> > typical residual capacitive reactance from a 160 meter 5/16 wave single >>> > wire folded counterpoise, AND provide enough coupling to make the >>> > transformer work, AND maintain a low enough loss to operate QRO without >>> > heating, or especially to operate QRP without further handicapping the >>> > operator with needless loss. This allows the builder of the "simple >>> > solution" to prune the wire to get resonance and remain somewhere > >>> around >>> >>> I'm trying to understand here what is magic about powdered iron. >>> >>> It is true you can't just use any random piece of ferrite. >>> But if the T300A-2 were replaced with LOW PERMEABILITY ferrite >>> having the same permeability as a T300A-2 core, it would produce >>> the required residual inductance. The loss of low permeability >>> ferrite is extremely low, probably lower than powdered iron. >>> Coupling is a function of how the turns are wound, not the core material. >>> >>> Am I missing something? >>> >>> Rick N6RK >>> >>> >>> >>> >>> ______________________________**_________________ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> >> >> ----- >> >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 10.0.1415 / Virus Database: 2108/4082 - Release Date: 12/15/11 >> >> > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
