[Elecraft] A couple of questions re: toroids

[Sverre Holm - LA3ZA]

You need to change the number of turns if you change the core of RFC11:

The original RFC11 was 100uH, and the suggested replacement was an
FT37-43 with "17-20 turns (not critical)". This core has A_L=420 nH/n^2,
giving an inductance between 121-168 uH. 

The FT50-43 has A_L=523 nH/n^2, which is not very different. The same
range of inductance is 15-18 turns. Its diameter is 0.5 inches instead
of 0.37 so Tom's comment on whether it fits applies.

The FT37-61 is the same size as the original one, but its A_L is only
55.3 nH/n^2 so the number of turns should be in the range 47-56, which I
doubt that you will be able to fit on that core.


73 Sverre
LA3ZA



> -----Original Message-----
> 
> >2. One of the mod notes says suggests RFC11 should be replaced with a
> >FT37-43 toroid. The closest I can get to that is either an 
> FT37-61 or 
> >FT50-43. Would I need to adjust the number of turns used if 
> I used the 
> >FT37-61? Having moved recently, my ARRL Handbook is in 
> storage so I can't 
> >check the toroid information and formula re: changes in 
> turns from one 
> >core material to another.
>