[HomeBrew] Need inductor help for W1FB Crystal Evaluator circuit from Jan 1990 QST

[Jim Pruitt]

I am trying to wind an rf choke for the W1FB Crystal Evaluator "A TEster for 
Crystal F, Q, and R" from the January 1990 QST.  The parts list specifies 15 
turns of #26awg magnet wire for 850 uh for L1.  I did not have any #26 but 
had some #24awg.  In using the Mini Ring calculator it says to use 53 turns 
of #30awg for an 850uh inductance on the FT37-43 core.

When I measured my 15 turn rf choke on the specified FT37-43 toroid I get 
about 115uh which is a far cry from the 850uh specified in the parts list.

The Mini Ring Calculator says that I should have 20 turns of #23AWG wire to 
get the 115uh inductance that I measured so that is not too far off but I am 
not sure why the W1FB article specifies 15 turns on the FT37-43 toroid if it 
should be 53 turns!

What am I missing?

Thank you.

Jim Pruitt