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Choice of iron powder toriod?
Hi,
Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Thanks, JEFF |
Jeff wrote:
Hi, Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Thanks, JEFF As far as I know, 7MHz is on the border between using one mix or the other. You'll see different Q's because details of winding, wire choice and mounting will affect Q, as would use of a core from another manufacturer (I don't know if anyone other than MicroMetals uses that system, but if they did I wouldn't count on it being standardized). If you're not going to be hitting it with really high power and if you don't need it to be highly resonant I wouldn't worry too much. If you're going for an engineered solution then you should make a number of "identical" coils and test them; just make sure that the coils you make are representative of what you'll be manufacturing. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
In article ,
"Jeff" wrote: Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Either grade 2 or 6 should work fine at 7 and 14 MHz. The Al values differ somewhat, so the number of turns to get a given inductance will be a little higher for grade 6 than grade 2. You only need to confirm that the number of turns required will actually fit on your T68-size core. For a given number of turns, the unloaded Q does peak at one frequency but is still quite good on either side of that frequency. Unless you have some real need to achieve the highest possible Q for a given inductance at the frequency of interest, I wouldn't worry too much about it. Wind the toroids, build the filter, and see how it works out! -- Joe |
Jeff wrote: Hi, Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Having just been playing with Micrometals cores myself, I gather that -2 is indeed the 'best' for higher frequencies. The local distributor says it's stocked in greater depth too. Have you also looked at Magnetics Inc and Arnold ? Graham |
Hello Jeff, wrote:
Hi, Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Not that this is an exact science but typically I switch from #2 to #6 around 10MHz. But I never design with high Q because that can be a pain in production. Regards, Joerg http://www.analogconsultants.com |
Get a copy of Amidon's catalog which gives detailed suggestions for powdered
iron and ferrite materials, based on many years of experience. www.amidoncorp.com Bill W0IYH "Jeff" wrote in message ... Hi, Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Thanks, JEFF |
On Wed, 12 Oct 2005 10:47:56 +1300, "Jeff"
wrote: Hi, Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Thanks, http://www.micrometals.com/ |
Thanks for all the suggestions. Ive got some Amidon T68-6 toroids to wind
up, and will test the completed filter on a spectrum analyser next week. JEFF "Jeff" wrote in message ... Hi, Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Thanks, JEFF |
From: "Jeff" on Tues, Oct 11 2005 2:47 pm
Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Been there, done that. In the practical case, what you can expect is a very slight change in insertion loss in the passband, perhaps a less sharp transition of attenuation at cutoff, depending on the type of highpass. It can be modeled in any SPICE analysis program with accuracy if you make a special model that adds a series R element computed from reactance divided by Q. For a highpass filter, the usual filter type has the inductor in shunt. In that configuration the inductor has a reactance directly proportional to frequency and will have little effect on the insertion loss in the passband. The equivalent series R due to Q won't matter much at 1/3 to 1/4 the cutoff frequency. It might matter on attenuation in the stopband region but the analysis on that is more difficult and a practical build-and-measure is the quicker way to go. For a lowpass filter, the usual configuration has inductors in series and there the Q of the inductors will affect insertion loss more. Those would use the lower frequency range for powder mix. In a highpass filter it is important that the capacitors have a minimum series inductance so that the 5x to 10x cutoff frequency isn't disturbed. Since capacitors are usually in series, their Q will effect the insertion loss. Fortunately, most capacitors will have a good Q up around 500+ and won't be a factor. Use what you have and measure the results (you've got a spectrum analyzer handy so that's taken care of). I made a fairly good, practical Synthesis-Analysis program for L-C filters that includes automatic modeling of (separately) all capacitor Qs and inductor Qs. I can attach that to private mail if you want it. Freeware. Proven by practical test comparison. |
Hello William,
Get a copy of Amidon's catalog which gives detailed suggestions for powdered iron and ferrite materials, based on many years of experience. www.amidoncorp.com Absolutely. I literally wore one of those catalogs to the point where you could see through several pages. Then there are the ARRL Handbook and their Antenna Book. Both well worth every penny. Regards, Joerg http://www.analogconsultants.com |
Hello Joerg, nice to meet you for the first time.
Bill W0IYH "Joerg" wrote in message ... Hello William, Get a copy of Amidon's catalog which gives detailed suggestions for powdered iron and ferrite materials, based on many years of experience. www.amidoncorp.com Absolutely. I literally wore one of those catalogs to the point where you could see through several pages. Then there are the ARRL Handbook and their Antenna Book. Both well worth every penny. Regards, Joerg http://www.analogconsultants.com |
Choice of iron powder toriod?
Hi Guys,
Results of the build and test were that the 7Mhz HPF worked very well with the "6" grade cores, but the 20Mhz LPF was crap (it used #6 as well). It started to roll off at 20Mhz as expected, dropped smoothly to -10dB by the time it got to 40Mhz, then stayed at 10dB at all frequencies above 40Mhz. I suppose the core should be a grade #10 or #12 instead of #6? or perhaps just a normal air core? JEFF "Jeff" wrote in message ... Thanks for all the suggestions. Ive got some Amidon T68-6 toroids to wind up, and will test the completed filter on a spectrum analyser next week. JEFF "Jeff" wrote in message ... Hi, Im confused regarding the choice of iron powder toroid for a 7Mhz high pass filter. I need to use a small size (T68) toroid. For the freq range, some reference texts say T68-2 is the one, others say T68-6" grade. I see differing "best Q range" specs for the 6 grade.....2-30Mhz......10-50Mhz...etc. Have similar need for 20Mhz LPF, but assume "6" is really the choice there. Any suggestions as to the relative differences and reasons to choose between grades 2 and 6 for the HPF in T68 size? Thanks, JEFF |
Choice of iron powder toriod?
"Jeff" wrote in message ... Hi Guys, Results of the build and test were that the 7Mhz HPF worked very well with the "6" grade cores, but the 20Mhz LPF was crap (it used #6 as well). It started to roll off at 20Mhz as expected, dropped smoothly to -10dB by the time it got to 40Mhz, then stayed at 10dB at all frequencies above 40Mhz. I suppose the core should be a grade #10 or #12 instead of #6? or perhaps just a normal air core? JEFF Then you haven't built the filter that you designed. The choice of core material will not affect the blow-by. If you measured the inductors at a low frequency, I would be pretty certain that you have way too much inductance at 20-40 MHz. W4ZCB |
Choice of iron powder toriod?
Hello Bill,
Hello Joerg, nice to meet you for the first time. Likewise. You name sounds very familiar, IIRC from a book about design of HF gear. Didn't you work at Collins in the good old days when they had mechanical filters in their gear? Regards, Joerg http://www.analogconsultants.com |
Choice of iron powder toriod?
Yes. I started at Collins Radio engineering department in 1964 and retired
from Rockwell Collins in 1990. For more info search Google for my name and my call sign. See QRZ.COM for W0IYH. See www.noblepub.com. Bill W0IYH "Joerg" wrote in message t... Hello Bill, Hello Joerg, nice to meet you for the first time. Likewise. You name sounds very familiar, IIRC from a book about design of HF gear. Didn't you work at Collins in the good old days when they had mechanical filters in their gear? Regards, Joerg http://www.analogconsultants.com |
Choice of iron powder toriod?
"William E. Sabin" wrote:
Yes. I started at Collins Radio engineering department in 1964 and retired from Rockwell Collins in 1990. For more info search Google for my name and my call sign. See QRZ.COM for W0IYH. See www.noblepub.com. Bill W0IYH Did you ever work on their microwave receiver designs? -- ? Michael A. Terrell Central Florida |
Choice of iron powder toriod?
Hello, Mike,
I had a little experience with some military L-band RF design (JTIDS), but that is about all. I have also designed miniature lumped-element filters for the 3 GHz region. But most of my work and also my ham radio experience have been at HF. Also, I am mostly, but not entirely, an analog specialist, which has put me somewhat into the Jurassic Age. Bill W0IYH "Michael A. Terrell" wrote in message ... "William E. Sabin" wrote: Yes. I started at Collins Radio engineering department in 1964 and retired from Rockwell Collins in 1990. For more info search Google for my name and my call sign. See QRZ.COM for W0IYH. See www.noblepub.com. Bill W0IYH Did you ever work on their microwave receiver designs? -- ? Michael A. Terrell Central Florida |
Choice of iron powder toriod?
Hello Bill,
... Also, I am mostly, but not entirely, an analog specialist, which has put me somewhat into the Jurassic Age. Not really. Newly minted engineers know remarkably little about analog techniques. Yet at the beginning and the end of circuits stuff usually needs to connect to the analog world. So don't be surprised when someone begs you to do just one more stint when you are past 90. Then again a SW engineer once told me that nothing is truly analog. There is always that smallest digital step, the quantum. Regards, Joerg http://www.analogconsultants.com |
Choice of iron powder toriod?
"William E. Sabin" wrote:
Hello, Mike, I had a little experience with some military L-band RF design (JTIDS), but that is about all. I have also designed miniature lumped-element filters for the 3 GHz region. But most of my work and also my ham radio experience have been at HF. Also, I am mostly, but not entirely, an analog specialist, which has put me somewhat into the Jurassic Age. Bill W0IYH There is no reason to apologize for being good with analog. ;-) I worked as a broadcast engineer during the time they announced the first memory chip, (1101) which was a slow, noisy 256 bit * 1 DRAM with very critical timing. I also did analog and digital work on the microwave equipment built at Microdyne, before L3-Com closed the Ocala plant. The reason I asked about the microwave equipment, I would like to meet the people who designed the C-band CATV receivers I had to maintain in the '80s. I always loved Collins equipment, till I ran into those radios. They had a horrible failure rate, and took over six months to have serviced by Collins. I think I still have a set of manuals for the fixed tuned, and the agile models. I started repairing them for United Video in 1982, and could return most of them to service the same day. -- ? Michael A. Terrell Central Florida |
Choice of iron powder toriod?
Hello Michael,
There is no reason to apologize for being good with analog. ;-) I worked as a broadcast engineer during the time they announced the first memory chip, (1101) which was a slow, noisy 256 bit * 1 DRAM with very critical timing. I also did analog and digital work on the microwave equipment built at Microdyne, before L3-Com closed the Ocala plant. Seems you started with digital stuff a year or two earlier than I did. My first RAM had a whopping 1024 bits. Not bytes, bits. 21...something, I could look it up since the device where its in still works. The reason I asked about the microwave equipment, I would like to meet the people who designed the C-band CATV receivers I had to maintain in the '80s. I always loved Collins equipment, till I ran into those radios. They had a horrible failure rate, ... But their HF radios were quite reliable. Unfortunately at that time out of my budget range, and so were those nice mechanical filters :-( Regards, Joerg http://www.analogconsultants.com |
Choice of iron powder toriod?
Joerg wrote:
Hello Michael, There is no reason to apologize for being good with analog. ;-) I worked as a broadcast engineer during the time they announced the first memory chip, (1101) which was a slow, noisy 256 bit * 1 DRAM with very critical timing. I also did analog and digital work on the microwave equipment built at Microdyne, before L3-Com closed the Ocala plant. Seems you started with digital stuff a year or two earlier than I did. My first RAM had a whopping 1024 bits. Not bytes, bits. 21...something, I could look it up since the device where its in still works. 2114? 1K * 4 bits? The reason I asked about the microwave equipment, I would like to meet the people who designed the C-band CATV receivers I had to maintain in the '80s. I always loved Collins equipment, till I ran into those radios. They had a horrible failure rate, ... But their HF radios were quite reliable. Unfortunately at that time out of my budget range, and so were those nice mechanical filters :-( Regards, Joerg http://www.analogconsultants.com I still have an unused 2.1 KHz Collins 455 KHz mechanical filter I bought at the Dayton hamfest years ago. Its a little narrow for voice, but it would be good for CW. I still like Collins equipment, just not their poorly designed CATV equipment. I wish I could afford a R-390 and felt well enough to do a complete restoration. :( -- ? Michael A. Terrell Central Florida |
Choice of iron powder toriod?
"Joerg" wrote in message
... Then again a SW engineer once told me that nothing is truly analog. There is always that smallest digital step, the quantum. So, digital is base two, and analog is base 1.6 x 10^19? ;-) Tim -- Deep Fryer: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms |
Choice of iron powder toriod?
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Choice of iron powder toriod?
Michael A. Terrell wrote: Joerg wrote: Hello Michael, There is no reason to apologize for being good with analog. ;-) I worked as a broadcast engineer during the time they announced the first memory chip, (1101) which was a slow, noisy 256 bit * 1 DRAM with very critical timing. I also did analog and digital work on the microwave equipment built at Microdyne, before L3-Com closed the Ocala plant. Seems you started with digital stuff a year or two earlier than I did. My first RAM had a whopping 1024 bits. Not bytes, bits. 21...something, I could look it up since the device where its in still works. 2114? 1K * 4 bits? Nah - 2102 1k * 1. Had 8 of 'em in in my homebuilt Nascom 1 computer which with a 2708 UVEPROM for the 'monitor' was all the RAM for system and user code and video store! Nevertheless, it was sufficient for a machine code program to run 'Lunar Lander', hee hee. Collins filters were regarded as the bees knees in UK ham circles but I never could afford one! 73 de G3VPC -- Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps Change 'news' to 'sewn' in my Reply address to avoid my spam filter. |
Choice of iron powder toriod?
Hello Tim,
Then again a SW engineer once told me that nothing is truly analog. There is always that smallest digital step, the quantum. So, digital is base two, and analog is base 1.6 x 10^19? ;-) Still, the digital guys kept telling us "Some day we'll get there and then you are going to be extinct". I am not worried at all... Regards, Joerg http://www.analogconsultants.com |
Choice of iron powder toriod?
Joerg wrote: Still, the digital guys kept telling us "Some day we'll get there ........ How long have they been saying that ???? ;-) Graham |
Choice of iron powder toriod?
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Choice of iron powder toriod?
Graham W wrote:
Michael A. Terrell wrote: Joerg wrote: Hello Michael, There is no reason to apologize for being good with analog. ;-) I worked as a broadcast engineer during the time they announced the first memory chip, (1101) which was a slow, noisy 256 bit * 1 DRAM with very critical timing. I also did analog and digital work on the microwave equipment built at Microdyne, before L3-Com closed the Ocala plant. Seems you started with digital stuff a year or two earlier than I did. My first RAM had a whopping 1024 bits. Not bytes, bits. 21...something, I could look it up since the device where its in still works. 2114? 1K * 4 bits? Nah - 2102 1k * 1. That was one early memory chip i don't recall using. Had 8 of 'em in in my homebuilt Nascom 1 computer which with a 2708 UVEPROM for the 'monitor' was all the RAM for system and user code and video store! Nevertheless, it was sufficient for a machine code program to run 'Lunar Lander', hee hee. Collins filters were regarded as the bees knees in UK ham circles but I never could afford one! The price was right, that day at the Dayton hamfest. ;-) 73 de G3VPC -- ? Michael A. Terrell Central Florida |
Choice of iron powder toriod?
"Joerg" wrote in message ... Hello Bill, ... Then again a SW engineer once told me that nothing is truly analog. There is always that smallest digital step, the quantum. Regards, Joerg Poor fella's got it bass ackward. 73, Steve, K,9;D.C'I |
Choice of iron powder toriod?
"Keith Williams" wrote in message t... In article , says... "Joerg" wrote in message ... Then again a SW engineer once told me that nothing is truly analog. There is always that smallest digital step, the quantum. So, digital is base two, and analog is base 1.6 x 10^19? ;-) Not really. Analog's bits are just smaller. ;-) -- Keith That's what he said... 10^18 smaller 73, Steve, K,9.D;C'I |
Choice of iron powder toriod?
"Keith Williams" wrote in message t... In article , says... Joerg wrote: Still, the digital guys kept telling us "Some day we'll get there ........ How long have they been saying that ???? ;-) We've been getting half the way there every two years or so. ;-) -- Keith Don-chya love it ? ! 73, Steve, K9DCI |
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