| Author |
Message |
Jeff
Guest
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 Posted:
Wed Oct 12, 2005 12:35 am Post subject:
Choice of iron powder toriod? |
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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
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Pooh Bear
Guest
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| Posted:
Wed Oct 12, 2005 12:35 am Post subject:
Re: Choice of iron powder toriod? |
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Jeff wrote:
| Quote: | 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 |
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Joerg
Guest
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| Posted:
Wed Oct 12, 2005 12:35 am Post subject:
Re: Choice of iron powder toriod? |
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Hello Jeff, wrote:
| Quote: | 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
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Tim Wescott
Guest
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| Posted:
Wed Oct 12, 2005 12:35 am Post subject:
Re: Choice of iron powder toriod? |
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Jeff wrote:
| Quote: | 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 |
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William E. Sabin
Guest
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| Posted:
Wed Oct 12, 2005 4:35 pm Post subject:
Re: Choice of iron powder toriod? |
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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" <jeff_164@NOSPAMhotmail.com> wrote in message
news:drW2f.17270$iM2.1412876@news.xtra.co.nz...
| Quote: | Hi,
Im confused regarding the choice of iron powder toroid for a 7Mhz high
pass
filter. I need to use a small size (T68) toroid. For the freq range, some
reference texts say T68-2 is the one, others say T68-6" grade. I see
differing "best Q range" specs for the 6
grade.....2-30Mhz......10-50Mhz...etc.
Have similar need for 20Mhz LPF, but assume "6" is really the choice
there.
Any suggestions as to the relative differences and reasons to choose
between
grades 2 and 6 for the HPF in T68 size?
Thanks,
JEFF
|
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Wes Stewart
Guest
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| Posted:
Wed Oct 12, 2005 4:35 pm Post subject:
Re: Choice of iron powder toriod? |
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On Wed, 12 Oct 2005 10:47:56 +1300, "Jeff"
<jeff_164@NOSPAMhotmail.com> wrote:
| Quote: | Hi,
Im confused regarding the choice of iron powder toroid for a 7Mhz high pass
filter. I need to use a small size (T68) toroid. For the freq range, some
reference texts say T68-2 is the one, others say T68-6" grade. I see
differing "best Q range" specs for the 6
grade.....2-30Mhz......10-50Mhz...etc.
Have similar need for 20Mhz LPF, but assume "6" is really the choice there.
Any suggestions as to the relative differences and reasons to choose between
grades 2 and 6 for the HPF in T68 size?
Thanks,
|
http://www.micrometals.com/ |
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Jeff
Guest
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| Posted:
Thu Oct 13, 2005 12:35 am Post subject:
Re: Choice of iron powder toriod? |
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Thanks for all the suggestions. Ive got some Amidon T68-6 toroids to wind
up, and will test the completed filter on a spectrum analyser next week.
JEFF
"Jeff" <jeff_164@NOSPAMhotmail.com> wrote in message
news:drW2f.17270$iM2.1412876@news.xtra.co.nz...
| Quote: | 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
|
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Guest
|
| Posted:
Thu Oct 13, 2005 8:35 am Post subject:
Re: Choice of iron powder toriod? |
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From: "Jeff" <jeff_...@NOSPAMhotmail.com> on Tues, Oct 11 2005 2:47 pm
| Quote: | 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.
LenAnderson@ieee.org |
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Joerg
Guest
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| Posted:
Sat Oct 15, 2005 12:35 am Post subject:
Re: Choice of iron powder toriod? |
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Hello William,
| Quote: | 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 |
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William E. Sabin
Guest
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| Posted:
Sat Oct 15, 2005 4:35 pm Post subject:
Re: Choice of iron powder toriod? |
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Hello Joerg, nice to meet you for the first time.
Bill W0IYH
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:vXW3f.1513$D13.478@newssvr11.news.prodigy.com...
| Quote: | Hello William,
Get a copy of Amidon's catalog which gives detailed suggestions for
powdered iron and ferrite materials, based on many years of experience.
www.amidoncorp.com
Absolutely. I literally wore one of those catalogs to the point where you
could see through several pages.
Then there are the ARRL Handbook and their Antenna Book. Both well worth
every penny.
Regards, Joerg
http://www.analogconsultants.com |
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Jeff
Guest
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| Posted:
Mon Oct 17, 2005 12:35 am Post subject:
Re: Choice of iron powder toriod? |
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Hi Guys,
Results of the build and test were that the 7Mhz HPF worked very well with
the "6" grade cores, but the 20Mhz LPF was crap (it used #6 as well). It
started to roll off at 20Mhz as expected, dropped smoothly to -10dB by the
time it got to 40Mhz, then stayed at 10dB at all frequencies above 40Mhz.
I suppose the core should be a grade #10 or #12 instead of #6? or perhaps
just a normal air core?
JEFF
"Jeff" <jeff_164@NOSPAMhotmail.com> wrote in message
news:mQe3f.76$S24.9081@news.xtra.co.nz...
| Quote: | 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" <jeff_164@NOSPAMhotmail.com> wrote in message
news:drW2f.17270$iM2.1412876@news.xtra.co.nz...
Hi,
Im confused regarding the choice of iron powder toroid for a 7Mhz high
pass
filter. I need to use a small size (T68) toroid. For the freq range,
some
reference texts say T68-2 is the one, others say T68-6" grade. I see
differing "best Q range" specs for the 6
grade.....2-30Mhz......10-50Mhz...etc.
Have similar need for 20Mhz LPF, but assume "6" is really the choice
there.
Any suggestions as to the relative differences and reasons to choose
between
grades 2 and 6 for the HPF in T68 size?
Thanks,
JEFF
|
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Harold E. Johnson
Guest
|
| Posted:
Mon Oct 17, 2005 12:35 am Post subject:
Re: Choice of iron powder toriod? |
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"Jeff" <jeff_164@NOSPAMhotmail.com> wrote in message
news:Cby4f.795$S24.49570@news.xtra.co.nz...
| Quote: | 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 |
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Joerg
Guest
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| Posted:
Tue Oct 18, 2005 7:15 am Post subject:
Re: Choice of iron powder toriod? |
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Hello Bill,
| Quote: | 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 |
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William E. Sabin
Guest
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| Posted:
Tue Oct 18, 2005 2:09 pm Post subject:
Re: Choice of iron powder toriod? |
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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" <notthisjoergsch@removethispacbell.net> wrote in message
news:MUY4f.1931$dO2.1625@newssvr29.news.prodigy.net...
| Quote: | 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 |
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Michael A. Terrell
Guest
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| Posted:
Tue Oct 18, 2005 4:35 pm Post subject:
Re: Choice of iron powder toriod? |
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"William E. Sabin" wrote:
| Quote: |
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 |
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