[UK-CONTEST] OT Where to buy FT240-31 or similar cores in the UK?

[Ian Burns]

Hello Ian,

Thank you  for the detailed reply.

I need to make up a  choke balun for 40-10m. Based on a little web 
reading I was going to try 8 turns of RG58 on FT240-31.

I'll look out for your radcom article. Given the current rate of 
progress May should be about right ;-)

73
Ian.



Ian White GM3SEK wrote:
> Peter Howson wrote:
>
>   
>>> From: uk-contest-bounces at contesting.com
>>> [mailto:uk-contest-bounces at contesting.com] On Behalf Of Ian Burns
>>> Sent: 25 February 2010 20:24
>>> To: UK Contesting
>>> Subject: [UK-CONTEST] OT Where to buy FT240-31 or similar cores in the UK?
>>>
>>>
>>> Please excuse the bandwidth, this is off topic but someone here will 
>>> probably know.
>>>
>>> Where can I buy FT240-31 or similar toroidal cores in the UK?
>>>
>>>       
>
>   
>> Sycom -- http://www.sycomcomp.co.uk/ -- have type 43 and 61 listed in 
>> 240 size.
>>
>> Also Modecomponents -- http://www.modecomponents.co.uk/ -- stock a good 
>> range but not this particular one. But Chris G8CHW may be able to get 
>> them for you.
>>     
>
> Be sure to buy the right grade of ferrite for what you want because 
> FERRITES ARE NOT INTERCHANGEABLE (yes, I am shouting :-)
>
> Fair-Rite grade 61 (six one) is good for choke baluns at 20-15-10m, but 
> the more recent 31 (three one) is *far* better for choke baluns at low 
> frequencies, and also for EMC chokes in non-transmitting applications at 
> any frequency.  The older and better-known grade 43 is a general purpose 
> HF grade, but better chokes can be made with 61 or 31 in their 
> respective frequency ranges.
>
> Dust iron cores (eg T200-6, without the F at the beginning) are 
> categorically NOT suitable for choke baluns or EMC chokes.
>
> If you're buying toroids for winding any kind of cable chokes, 2.4in is 
> the only practical size, ie FT240-xx. Smaller toroids don't have enough 
> room to wind multiple turns. Small-hole beads are very poor value 
> compared with toroids, which means that people often don't use enough 
> beads and then wonder why their chokes don't work (or only work in 
> situations that are 'soft targets').
>
> Among the UK amateur dealers, Sycom stock the FT240-43 and -61; JAB list 
> only the FT240-61 but it isn't available; and Mode Components do not 
> list any of these large toroids. Despite heavy hints, no UK amateur 
> dealer stocks the FT240-31... but maybe this isn't surprising, because 
> they have to buy from the USA on exactly the same terms as an individual 
> importer.
>
> As far as I know, the only sources for the FT240-31 are in the USA but 
> you need to order in some quantity:
>
> * Mouser (www.mouser.com) have a free Fedex shipping deal on orders over 
> £50
>
> * Farnell (uk.farnell.com) charge £15.95 per order on items from their 
> US company Newark.
>
> Both companies stock FT240-31 (but not the FT240-61 or -43). In both 
> cases you will have to pay VAT but they handle the importation process. 
> Farnell are very quick - you're billed in the UK and they ship by UPS 
> the same day (US time) with no further delivery/collection charges. I 
> haven't personally used Mouser so the details may be different.
>
> I will not use Amidon ever again. Prices are far higher than Newark or 
> Mouser, and a whole sheet of "FT240-31" bought in the USA at great 
> expense and hand carried back, turned out to be grade 43. Essentially 
> Amidon take the obscure Fair-Rite stock numbers, change them to a more 
> readable "FTxxx-yy" format... and then double the price.
>
> Newark and Mouser use the original Fair-Rite stock numbers; if anyone 
> wants them, please e-mail.
>
> Having said all that, I've recently been working on a range of ferrite 
> chokes that avoid having to buy big toroids at all. They are based on 
> some Fair-Rite 43 beads which are a standard Farnell UK stock item (so 
> there's no US order surcharge). Performance isn't quite as good as the 
> very best chokes using multiple FT240 toroids, but better than any 
> straight string of 20-30 beads. Above all they are far more 
> cost-effective given the prices we have to pay for 'named ferrite' in 
> the UK.
>
> Details will be in May Radcom. I'm also looking for some beta testers so 
> if anyone is genuinely intending to make some chokes in the very near 
> future (as opposed to generally curious), please e-mail.
>
>
>
>