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Tuesday, January 24, 2012

Toroidal Transformers: Does Size Matter?

I continue to tweak and peak the JBOT amplifier in the Azores 17 SSB transmitter. On this version I used some FT-50-43 toroidal cores instead of the smaller FT-37-43 cores recommended by Farhan. This morning I was experimenting with the output transformer. I seem to get noticeably more output with a transformer made with four FT-37-43 cores than I do with one made with four larger FT-50-43 cores.

I noticed something similar on my previous JBOT: performance improved when I switched from some relatively large binocular cores and went to the recommended FT-37-43.

So, what do you guys think? Could there be lower losses using the smaller cores? Any other reason why the smaller transformers seem to be doing better?

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  1. Well, I doubt that it's core saturation. Did you adjust the number of windings to keep the inductance the same as the smaller core? If not, the inductance (hence the inductive reactance) will be considerably higher. My estimate is 20% higher. Naturally if you adjust the number of turns you will need to re-do all the windings to maintain the correct transformation ratio.

    Now, is this the cause of the problem? I dunno, HA!

    It would be very interesting to know the material Farhan's binocular cores are made of or at least the inductance of the secondary winding of T3 using his core.

    73.......Steve Smith WB6TNL

  2. How silly of me. Of course, the ratio is 1:1. 5 + 5 : 10 turns.


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