Use of type 31 ferrite as coax common mode choke
 

Roy Lewallen wrote:
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.


A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has
roughly the same or a little higher total complex permeability than 73
over most of the lower HF range and same or higher than 43 on up to 100
MHz. So it should be a good ferrite to use for very wide band
applications. However, Table 1 shows that it's available in large parts
only. Type 43 is very widely available in a wide variety of sizes, so
you might have a lot more luck getting cores of the sizes you need in
type 43.

Large, in this context, isn't all that big. You can't get it in tiny
ferrite beads to slip over a AWG30 wire. You can get it in 0.485" OD
0.5" long beads with a 0.2" hole in the middle.... $0.42 each from
Mouser. Similar snap on cases too..

Small, for Fair-rite, means things like those little 1/4" diameter multi
hole cores for making wound EMI filters, or chip components.

I buy it in 2.4" toroids so I can put multiple turns of coax on.

Use of type 31 ferrite as coax common mode choke
 

Owen Duffy wrote:
"J. Mc Laughlin" wrote in
:


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.


Mac,

Whilst playing around with models of a Guanella balun, I did compare #31
sleeves with Walt's design using #73 sleeves over the range 1 - 30MHz.

My model of Walt's balun is at http://www.vk1od.net/balun/W2DU/index.htm
. I obtained different results to Walt's measurements, but I think that
is because Walt's measurements were affected by stray capacitance that
was worse than would apply to that type of balun in service.

I also modelled some Fair-rite 2631480002 sleeves and found a slightly
longer choke (12 cores at 25.4mm ea) was needed to achieve about the same
choking impedance up to about 12MHz, above which the #31 choke had higher
impedance than the #73 one.

Whilst I modelled these sleeves because they suited the application, I
have not seen anyone selling them in small quantities.


Mouser has them.. Don't know if they ship in VK land or not. Shipping
of what is basically iron bars is going to be punitive. FairRite has
distribution there (Specialised Conductives in Victoria), but perhaps
not retail. But, since one typically isn't looking to buy just one, but
dozens, this might not be a problem.

One should be careful about modeling these things.. that gets you close,
but parasitics are a real bugabear. K9YC's paper has actual
measurements on actual chokes made with a variety of cores (which are
decidedly non-trivial to make..)

Snelling's book is the tome of choice, if you can find it...

Use of type 31 ferrite as coax common mode choke
 

JIMMIE wrote:
On Apr 21, 10:21 am, "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.

--
J. McLaughlin; Michigan, USA
Home:


I think the type 31 is entended for use on things like power cords and
computer cables to prevent unwanted radiation/pickup of RF. Im not
sure how well it would meet your requirements but I suspect it may be
OK in a receive only situation. I have tried using some unknown types
of cores removed from various computer cables for a balun and the
vinyl tape holding them to the coax got very soft when they heated up.
Perhaps some experimentation using these cores is in order.

Jimmie

#31 is specifically made for our kind of application (transmitting).. it
has a higher temperature rating than the other popular materials. The
key on managing dissipation is making sure you have enough impedance so
that the current is small.

It's a long way from the miscellaneous stuff used for RFI on power cords
and keyboards..

Use of type 31 ferrite as coax common mode choke
 

Jim Lux wrote:
I buy it in 2.4" toroids so I can put multiple turns of coax on.

Jim, have you or anyone else you know of taken
a look at 'K' material?
--
73, Cecil http://www.w5dxp.com

Use of type 31 ferrite as coax common mode choke
 

The following is a copy of my message posted earlier to the general
group, but I had wanted to preply directly to this topic as it's very
pertinent to the discussion of ferrites, so here is the message again
(sorry if you see this twice).

Greetings All,

Saw the posts about Mix 31 ferrites, which I use on my mobile
installations with good results, using a HiQ 5/160 antenna and Icom
IC7000.
If anyone is interested, I recently posted on my web site a document
the describes the installation of ferrites for HF installations: :
www.repdesign.us ,
(go to the "Downloads" page (left side of screen towards the bottom),
and go to the third group to download or simply open to read the PDF
document).

This is based on what has worked well for me, information from Fair
Rite's web
site, and ideas from various past posings. Also listed is a partial
list of suppliers - as always check the prices as they can vary a
lot!

Check it out and let me know (direct email) if you have any other
suggestions and if you find this useful, as this is meant to be a
"continous improvement" document. I also plan to write additional
guidelines as time permits.

73,
Dick Post, N7EMW
www.repdesign.us


On Apr 21, 10:21*am, "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.

--
J. McLaughlin; *Michigan, USA
Home:

Use of type 31 ferrite as coax common mode choke
 

Jim Lux wrote in
:

Mouser has them.. Don't know if they ship in VK land or not.

Yes, but shipping anything from them and some other big suppliers is
prohibitive.

Shipping of what is basically iron bars is going to be punitive.
FairRite has distribution there (Specialised Conductives in Victoria),
but perhaps not retail. But, since one typically isn't looking to buy
just one, but dozens, this might not be a problem.

For some reason, magnetics ex USA through Aussie distributors / retailers
are outrageously expensive. Typically on Ebay one can buy 10 cores ex USA
for the price of one from a Aussie retailer.

One should be careful about modeling these things.. that gets you
close, but parasitics are a real bugabear. K9YC's paper has actual

Yes, agreed. I have made measurements of a number of choke
configurations, albeit only with a TAPR VNA (hate the software), and
calibrated my models to the measured values. It is certainly a balancing
act to put enough turns on a toroid to get high Z, but few enough turns
that Z hasn't gone seriously south at the top end of the desired range.

Predicting magnetics behaviour is a bit of a black art, but models help
to guide one to a better understanding of behaviour.

It is little wonder than balun specifications, where they are given, bear
little relation to the intended application.

Owen

Use of type 31 ferrite as coax common mode choke
 

Dear Roy: The use of small and large in this context is not clear. So far,
I have found the sizes of type 31 to be about the right size. On the other
hand, some of the 7X types seem only to be available in sizes that are too
small.

Your point that the type, and its performance, is only part of the issue.
One must also have parts that fit.

Thanks, Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Roy Lewallen" wrote in message
news:JZSdnd4om7o7-5DVnZ2dnUVZ_jCdnZ2d@easystreetonline...
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.

A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has
roughly the same or a little higher total complex permeability than 73
over most of the lower HF range and same or higher than 43 on up to 100
MHz. So it should be a good ferrite to use for very wide band
applications. However, Table 1 shows that it's available in large parts
only. Type 43 is very widely available in a wide variety of sizes, so you
might have a lot more luck getting cores of the sizes you need in type 43.

Roy Lewallen, W7EL

Use of type 31 ferrite as coax common mode choke
 

Dear Ian (also my father's name): Thank you for your note. It is a
mystery to me why those who sell via the Internet do not work hard at
keeping their sites up-to-date. 73, Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Ian White GM3SEK" wrote in message
...
Roy Lewallen wrote:

A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has
roughly the same or a little higher total complex permeability than 73
over most of the lower HF range and same or higher than 43 on up to 100
MHz. So it should be a good ferrite to use for very wide band
applications. However, Table 1 shows that it's available in large parts
only. Type 43 is very widely available in a wide variety of sizes, so you
might have a lot more luck getting cores of the sizes you need in type 43.

Roy Lewallen, W7EL


Amidon do stock some type 31 products, including FT-240-31 toroids and the
large beads for RG213, but they aren't listed on the website.

Part numbering is the same as normal, so simply substitute a "31" in the
part number you wish to order, and then call 1-800-898-1883.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Use of type 31 ferrite as coax common mode choke
 

Dear Jim: Right. Small and large have somewhat unexpected uses by
Fair-Rite.

Thanks for the useful observation, 73 Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Jim Lux" wrote in message
...
Roy Lewallen wrote:
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.


A fairly brief look at the graphs (Figs. 6 - 8) shows that type 31 has
roughly the same or a little higher total complex permeability than 73
over most of the lower HF range and same or higher than 43 on up to 100
MHz. So it should be a good ferrite to use for very wide band
applications. However, Table 1 shows that it's available in large parts
only. Type 43 is very widely available in a wide variety of sizes, so you
might have a lot more luck getting cores of the sizes you need in type
43.

Large, in this context, isn't all that big. You can't get it in tiny
ferrite beads to slip over a AWG30 wire. You can get it in 0.485" OD 0.5"
long beads with a 0.2" hole in the middle.... $0.42 each from Mouser.
Similar snap on cases too..

Small, for Fair-rite, means things like those little 1/4" diameter multi
hole cores for making wound EMI filters, or chip components.

I buy it in 2.4" toroids so I can put multiple turns of coax on.

Use of type 31 ferrite as coax common mode choke
 

Dear Roy: I think that I looked at those sites, however I will take
another look.

73, Mac N8TT

--
J. McLaughlin; Michigan, USA
Home:
"Roy Lewallen" wrote in message
news:QqqdndKq2bKv9ZDVnZ2dnUVZ_gOdnZ2d@easystreeton line...
J. Mc Laughlin wrote:

P.S. I will also appreciate ideas about places to purchase ferrite in
addition to Mouser.


You might try Amidon (https://www.amidoncorp.com/) or the Wire Man
(http://thewireman.com/baluns.html#901). I don't think I've bought
anything from Amidon since Bill Amidon sold it, but see their brand on
small quantities of cores at the local electronics shop. Press Jones, the
Wire Man, is great to do business with.

Roy Lewallen, W7EL