#toroid #20m #40m #toroid #20m #40m


The toroids for L1  - L4 are red and yellow and I think they are T37-2 and T37-6 types: not sure about this. I don't know the technical nomenclature or the color coding standard is for describing these toroids so what exactly does the T37-2 mean?  There are iron powdered cores that KS_Cables_N_More sells via EBay. The physical dimensions look like they are the same.  Are these the correct ones I need to buy if I want replacement toroids to experiment around with to mimic the LPF circuitry of these kits?  Also if I did make a prototype of these LPF on a breadboard and then experimented around with it using a tracking generator/SA and my NanoVNA, I'll terminate the LPF with a 50 ohm load, but I don't know what I should use for the input impedance. I'm thinking of using a 10K termination for the front end of the LPF.


The 37 refers to the diameter in inches ie. 0.37" and the 2 or 6 refers to the "mix" of the powdered iron toroid. Type 2 works best below 10MHz and Type 6 works well from 3-40 MHz. Type 7 is popular for certain types of oscillators, given it's stability.

Micrometals has good documentation for their products, as does Kits and Parts. Some Ebay cores can be quite lossy...