Re: BITX-40

Arv Evans K7HKL <arvevans@...>


Since I used Farhan's air-cored toroid idea (small plastic rings as coil formers) I am probably not the best person to answer your question about which ferrite type toroid core material is best for your application.  Possibly some other member of the BITX20 forum could answer this question?

As to wire size, the currents involved are rather small, so the real question seems to be how small can the wire be and still be reasonably easy to work with in winding the transformers.  For my plastic core transformers I used #26AWG which is approximately 0.404 mm or British SWG-29.   

The number of turns will depend to some extent on which ferrite core material you use.  There are published tables which show the number of turns required for a specific inductance for each type of ferrite mix.

For the non-resonant transmission-line transformers used in the mixers it is usually adequate to have between 7 and 11 turns per winding if you are using ferrite based toroid cores.  I am using 16 turns with my air-core transformers.

Arv - K7HKL


Please, I am constructing the BITX-40 v3 version of Rahul, but I want to construct it (T1, T2 and T3) with FT37-61 or FT37-43 which of the two would be better? And how many wire returns AWG would be necessary?
Thank You!
Vy's 73
Uelson de Almeida Toyama - PY2UAT

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