Barett wrote:

What is the T200-2 Toriod used for and why is it good for that purpose?

Tuned circuits e.g. antenna matching & filters, that's about it !

#6 is even worse for HF broadband transformers

Too many folks use iron powder cores of all types for totally
unsuitable purposes.

UKM

Does any one know where I can purchase some Ferrite rings type 31
material from in the UK?

and thanks to UKM.


UKM is right: iron powder material is not suitable for RF chokes.

Well done for finding out about Fair-Rite 31 material - you must have
been reading Jim Brown K9YC's tutorials on www.audiosystemsgroup.com
:-)

None of the UK amateur suppliers seems interested in stock large toroids
or beads in this material (and believe me, I have tried) so the next
best thing is to order from the USA.

As Jim Brown has often advised, order directly from an industrial
supplier in the USA, and not one of the "amateur" suppliers. When
ordering from outside the USA, the most cost-effective route is probably
either Mouser or Farnell because they handle the international shipping
and Customs clearance, so you don't get hit for the same one-off charges
and 'collection fees' that a personal import would.

There is no import duty on these electronic parts, but of course you
still have to pay 17.5% VAT on the whole bill.

The best value will depend on the size of your order, and of course on
any special offers, but it's sure to be cheaper than any of the US
amateur suppliers like Amidon. Mouser have a free Fedex shipping deal on
orders above GBP50. Farnell can supply US stock from their Newark
Electronics affiliate with an extra charge of GBP15 per order (they
removed this charge for the whole of January, and maybe this offer might
be repeated).

The Fair-Rite part number for the 2.40in #31 toroid is 2631803802. Paste
this number into the search fields at http://gb.mouser.com and
http://uk.farnell.com and search out the best deal.

Ah, too bad... Mouser currently have an 11 week lead time.

Farnell have 95 of them at Newark Electronics. (Ignore the wrong
information about "43 shield beads". Farnell/Newark confirmed that the
cores really are #31, but it may take some time to correct the web
page.)

Also worth considering is the giant #31 clamp-on bead 0431177081... an
exercise for the reader.



--

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

"Ian White GM3SEK" wrote in message
...
Barett wrote:

What is the T200-2 Toriod used for and why is it good for that purpose?

Tuned circuits e.g. antenna matching & filters, that's about it !

#6 is even worse for HF broadband transformers

Too many folks use iron powder cores of all types for totally unsuitable
purposes.

UKM

Does any one know where I can purchase some Ferrite rings type 31 material
from in the UK?

and thanks to UKM.


UKM is right: iron powder material is not suitable for RF chokes.

Well done for finding out about Fair-Rite 31 material - you must have been
reading Jim Brown K9YC's tutorials on www.audiosystemsgroup.com :-)

None of the UK amateur suppliers seems interested in stock large toroids
or beads in this material (and believe me, I have tried) so the next best
thing is to order from the USA.

As Jim Brown has often advised, order directly from an industrial supplier
in the USA, and not one of the "amateur" suppliers. When ordering from
outside the USA, the most cost-effective route is probably either Mouser
or Farnell because they handle the international shipping and Customs
clearance, so you don't get hit for the same one-off charges and
'collection fees' that a personal import would.

There is no import duty on these electronic parts, but of course you still
have to pay 17.5% VAT on the whole bill.

The best value will depend on the size of your order, and of course on any
special offers, but it's sure to be cheaper than any of the US amateur
suppliers like Amidon. Mouser have a free Fedex shipping deal on orders
above GBP50. Farnell can supply US stock from their Newark Electronics
affiliate with an extra charge of GBP15 per order (they removed this
charge for the whole of January, and maybe this offer might be repeated).

The Fair-Rite part number for the 2.40in #31 toroid is 2631803802. Paste
this number into the search fields at http://gb.mouser.com and
http://uk.farnell.com and search out the best deal.

Ah, too bad... Mouser currently have an 11 week lead time.

Farnell have 95 of them at Newark Electronics. (Ignore the wrong
information about "43 shield beads". Farnell/Newark confirmed that the
cores really are #31, but it may take some time to correct the web page.)

Also worth considering is the giant #31 clamp-on bead 0431177081... an
exercise for the reader.



--

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

I only need about 3 of them I think, so the postage is a killer
unfortunately.

I have found some FT140-43's.

Do you know if I stacked 3 Ferrite FT140-43's rings and wound 6 winding of
RG58cu through, what would the maximum impedance Ohms could I expect @
3.5MHz?

Also how much impedance could I expect to gain every time I added another
FT140-43 ferrite onto the stack?

Thanks for you links and info.

On Feb 9, 3:33*pm, "Barett" wrote:
"Ian White GM3SEK" wrote in ...





Barett wrote:

What is the T200-2 Toriod used for and why is it good for that purpose?

Tuned circuits *e.g. antenna matching & filters, that's about it !

#6 is even worse for HF broadband transformers

Too many folks use iron powder cores of all types for totally unsuitable
purposes.

UKM

Does any one know where I can purchase some Ferrite rings type 31 material
from in the UK?

and thanks to UKM.

UKM is right: iron powder material is not suitable for RF chokes.

Well done for finding out about Fair-Rite 31 material - you must have been
reading Jim Brown K9YC's tutorials onwww.audiosystemsgroup.com:-)

None of the UK amateur suppliers seems interested in stock large toroids
or beads in this material (and believe me, I have tried) so the next best
thing is to order from the USA.

As Jim Brown has often advised, order directly from an industrial supplier
in the USA, and not one of the "amateur" suppliers. When ordering from
outside the USA, the most cost-effective route is probably either Mouser
or Farnell because they handle the international shipping and Customs
clearance, so you don't get hit for the same one-off charges and
'collection fees' that a personal import would.

There is no import duty on these electronic parts, but of course you still
have to pay 17.5% VAT on the whole bill.

The best value will depend on the size of your order, and of course on any
special offers, but it's sure to be cheaper than any of the US amateur
suppliers like Amidon. Mouser have a free Fedex shipping deal on orders
above GBP50. Farnell can supply US stock from their Newark Electronics
affiliate with an extra charge of GBP15 per order (they removed this
charge for the whole of January, and maybe this offer might be repeated).

The Fair-Rite part number for the 2.40in #31 toroid is 2631803802. Paste
this number into the search fields athttp://gb.mouser.com*and
http://uk.farnell.comand search out the best deal.

Ah, too bad... Mouser currently have an 11 week lead time.

Farnell have 95 of them at Newark Electronics. (Ignore the wrong
information about "43 shield beads". Farnell/Newark *confirmed that the
cores really are #31, but it may take some time to correct the web page..)

Also worth considering is the giant #31 clamp-on bead 0431177081... an
exercise for the reader.

--

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

I only need about 3 of them I think, so the postage is a killer
unfortunately.

I have found some FT140-43's.

Do you know if I stacked 3 Ferrite FT140-43's rings and wound 6 winding of
RG58cu through, what would the maximum impedance Ohms could I expect @
3.5MHz?

Also how much impedance could I expect to gain every time I added another
FT140-43 ferrite onto the stack?

Thanks for you links and info.- Hide quoted text -

- Show quoted text -

Take a look at

http://www.karinya.net/g3txq/chokes/

http://audiosystemsgroup.com/RFI-Ham.pdf

http://www.yccc.org/Articles/W1HIS/C...S2006Apr06.pdf

Mouser and Newark are you only real options, watch out for special
shipping offers and take advantage of them when they occur.

The giant #31 clamp-on beads 0431177081 are expensive but equivalent
to three 240 sized rings.

UKM

Also how much impedance could I expect to gain every time I added another
FT140-43 ferrite onto the stack?


You need to double the number of beads each time to make a noticable
difference.

For worthwhile common mode suppression you need at least ten and
ideally eighty type 43 beads over a length of cable.

It's more cost effective to wind more turns. 2 x the turns 4 x the
inductance.

UKM

On 2/9/2010 9:32 AM, UKMonitor wrote:


Also how much impedance could I expect to gain every time I added another
FT140-43 ferrite onto the stack?


You need to double the number of beads each time to make a noticable
difference.

For worthwhile common mode suppression you need at least ten and
ideally eighty type 43 beads over a length of cable.

It's more cost effective to wind more turns. 2 x the turns 4 x the
inductance.

UKM

If I am understanding the data associated with the device (bead) you
suggested, correctly--"EMI/RFI Dämpare och ferriter Z=375 OHM @ 100
MHz", it would, indeed, take a number of them. Personally, I like to
see a Z of 10 times that of the Z of the coax. For example, for 50 ohm
coax, I would like to see a choke which would provide a "resistance" (Z)
of 5,000 ohms to any rf currents which would be tempted to ride the
braid(radiate.) While 10 of these devices may be sufficient (and would
be affected\effected by the frequencies they would be used with); I
would probably choose to use a few more.

If cost\design-needs is\are any sort of factor(s) in your design needs,
I would tend to go multiple turns on a proper core size(power handling
requirements of correct material(frequency(s) designed for.)

While ferrite may have advantages over iron cores at vhf\uhf\shf--and
become quite noticible, I have found any losses or heating tolerable at
hf and below--again, given proper core size\material--and I have used
them at much higher freqs.

The beads you mentioned are very useful though. If in a hurry, if
experimenting and time is valuable--just slap too many on the line and
go for it!

Regards,
JS

For the 4:1 Ruthroff balun Type 43 or 31 is not ideal for this
purpose, use approx 12 bifilar turns on a FT240-61 core.

Wind the transformer with twin figure of eight speaker cable which is
OK for low power up to about 100w. Use thin 100 ohm twin feeder sold
by Spectrum Communications for higher power levels.

UKM

On Tue, 9 Feb 2010 15:33:57 -0000, "Barett"
wrote:

Also how much impedance could I expect to gain every time I added another
FT140-43 ferrite onto the stack?

Hi OM,

Z varies by the square of turns THROUGH the center (turns are always
integers, not fractions). Z is a function of formulation (the mix of
the ferrite) which defines the optimum band(s) of operation. Z is
also a function of mass, but it doesn't take much, a small bead that
comfortably girdles RG58 will present several 10s of Ohms Z. Z is a
function of frequency, but most ferrites exhibit very mild shifts in Z
as frequency changes. You can chain beads or toroids to build up your
Z. You typically want your choke at least 3X the Z of the feedpoint -
10X is very much more preferred.

As for resources and cost, go to your nearest computer monitor
recycler and obtain any deflection coils that may still be around in
this era of flat screens. They have been reportedly quite useful.

If you do this, you will have to characterize the formulation of the
available ferrite through experimentation. If you have an antenna
computerized analyzer, you can measure this directly. If not, this
may take invention and thought (and more posts here).

73's
Richard Clark, KB7QHC

"Barett" wrote in
:

....
I only need about 3 of them I think, so the postage is a killer
unfortunately.

We experience the same problem here in VK. Local resellers charge very
high prices, and many US suppliers charge very high shipping on
magnetics.

Another option is to look on Ebay, Ebay sellers who really want to sell
internationally have reasonable prices... but be prepared for excessive
shipping quotes from some.


I have found some FT140-43's.

You could use these to make a common mode choke, but the physical size
limits the amount of heat that they can dissipate and the power rating.


Do you know if I stacked 3 Ferrite FT140-43's rings and wound 6
winding of RG58cu through, what would the maximum impedance Ohms could
I expect @ 3.5MHz?

Also how much impedance could I expect to gain every time I added
another FT140-43 ferrite onto the stack?

At low frequency, the impedance is close to proportional to the square of
turns, and proportional to the number of cores stacked but for a core of
this type, the inductor will probably be self resonant in the HF range
and stacking cores increases self capacitance and reduces the self
resonant frequency and the above approximation does not apply so well.

I should stress that self resonance isn't necessarily bad for these types
of lossy inductors, you should put aside Rules of Thumb (ROT) that say to
never use an inductor above its self resonant frequency.

I have written a short article entitled "A method for estimating the
impedance of a ferrite cored toroidal inductor at RF" which you may find
interesting, it is at http://vk1od.net/blog/?p=806 .

Is Neosid still selling product in the UK? I believe they stopped
manufacture, but they may be selling product.

In answer to the shipping cost issue, I went looking for a locally
available core that suited a general purpose HF common mode choke, and
Neoside produce a core larger than FT240 with a material that is a good
choice for the purpose, similar to Fair-rite #52. I describe the design
at http://vk1od.net/blog/?p=581 . Moving house has delayed completion of
this, the design is done, the materials are here, I just have to
construct one in a box and measure its common mode impedance to calibrate
the amount of equivalent shunt capacitance. An alternative would be a
stack of two FT240-52 cores.

Everybody, and every manufacturer has a recipe for common mode chokes,
but if you do not provide a plot of common mode impedance, preferably R
and X separately, then you might reasonably question the recipe.

None so more than the commercial purveyors of the magic Caronlina Windom
which calls out aspects many of us might regard as a disadvantages as
positive features (sheer marketing spin) and depends on undescribed
proprietary components.

Owen

Owen Duffy wrote in
:

....
Everybody, and every manufacturer has a recipe for common mode chokes,
but if you do not provide a plot of common mode impedance, preferably
R and X separately, then you might reasonably question the recipe.

Aargh!

Everybody, and every manufacturer has a recipe for common mode chokes, but
if *they* do not provide a plot of common mode impedance, preferably R and
X separately, then you might reasonably question the recipe.

Barett Wrote:



The Fair-Rite part number for the 2.40in #31 toroid is 2631803802. Paste
this number into the search fields at http://gb.mouser.com and
http://uk.farnell.com and search out the best deal.

[...]

I only need about 3 of them I think, so the postage is a killer
unfortunately.

I have found some FT140-43's.

Do you know if I stacked 3 Ferrite FT140-43's rings and wound 6 winding of
RG58cu through, what would the maximum impedance Ohms could I expect @
3.5MHz?


You're in luck, as I happen to have a few FT-140-43, and the measurement
equipment is out on the bench.

That 3-core choke has its best performance around 15MHz (peaking at 4000
ohms, broadband and predominantly resistive, which is quite a good
result) but at 3.5MHz it's only about 1900 ohms and mostly inductive.

Also how much impedance could I expect to gain every time I added another
FT140-43 ferrite onto the stack?

I had only one more to add, which moved the peak down to 12MHz, 5000
ohms, but only added a few hundred ohms at 3.5MHz.

Clearly these cores are not the best for your application.

I'm working on a better approach from the new ARRL 2010 handbook, which
uses cores that *are* available in the UK and gives the best "value for
ferrite" of anything I've seen. Publication is due in the May Radcom,
but I may be able to give some previews in the next few weeks.



--

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