BTW, the 37 in FT37-43 means its size is 0.37 inch, and 43 is the material mix of the toroid. So yes, they are very small. If you have fat fingers, the FT50-43 is a bit bigger. Use about one turn less for the same inductance.
The FT37-61 toroid has a much lower permittivity than FT37-43, translating into a far lower inductance. I'd guess 5 to 10 times less inductance. It might work, but why go through the trouble? FT37-43 are pretty common. In fact, you can get 10 via Amazon for less than $7.
I would not use the FT37-6. It has low permittivity, and I believe higher losses at RF.
Hello,?
I was hoping someone could help me with choosing the correct toroid for a scratch built bitx40.
The circuit description on hfsignals below.
The inductors used on the board as follows:
- L1, L2, L3?: 6uh, 40 turns on T30-6 core
- L4?: Only needed the analog VFO, 9uh, 50 turns on T30-6 core
- L5?: just a jumper on the standard bitx40, you will have to an inductor of a few uh to pull the BFO down for upper-sideband
- L6, L7?: 1.1 uh, 17 turns on T30-6 core
- L8?: 10 turns on FT37-43
- T1,T2,T4,T5,T6,T7?: 10 turns trifilar on FT 37-43 core
- I could not find FT37-43 so i ordered the FT37-61
- these cores look way smaller than any build i have seen.
- Thanks in advance for any advice.?
- JR
