"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.