Newark or Mouser often have ok prices for the "FT-240-31" large toroid
core. Chris KF7P.com has had them on sale at times. I've bought from
all three.
http://www.newark.com/fair-rite/2631803802/ferrite-core-cylindrical-119ohm/dp/43K4703?ost=2631803802&iscrfnonsku=false&ddkey=http%3Aen-US%2FElement14_US%2Fsearch
http://www.mouser.com/ProductDetail/Fair-Rite/2631803802/?qs=%2fha2pyFadujg9vFABS5CZWkClXV4tmC2yGMdLN2jsic%3d
An interesting trade-off is the price performance of the "big clamp on"
vs a stack of the FT-240-31's. There is a lot of ferrite in the clamp
on and it is very convenient for existing cables but needs securely
closed tight with tie wraps or Scotch 33 for good performance.
A 1/2" wide cloth/glass tape is very handy to tie the FT-240-31 stacks
together before winding the coax. RG142 TFE coax can be wound fairly
tight on a stack and easily handles QRO power.
Grant KZ1W
On 9/20/2017 7:31 AM, Dave Sublette wrote:
Thanks for all the suggestions on the RF choke. I read the article by K9YC and
concluded that the best approach wold be to wind RG8X around 6 Fair-Rite toroids made
from type 31 material and 2.4 inches in diameter. The big problem is they are listed
at over $17 each from the distributors. I will need 18 of them eventually. 6 each
for this dipole and two more yagis. That’s a large price tag, but still
cheaper (and better performing) than the commercial units available, according to K9YC.
I have (again at the suggestion in the paper by K9YC) sent a request for quit to Fair-Rite, asking
what quantity I would have to buy in order to get “a decent price”. It might work out
that I could make a large purchase and offer kits of toroids to the group. I’m not looking
to make money. I only want to have a good choke at the lowest price I can find.
I may put the antenna up with a temporary choke on it and replace it when/if I
can get the toroids.
I will keep you informed as to what I find.
I appreciate your inputs on this project. It’s been fun.
Dave, K4TO
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