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Re: More primary L needed

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

Hi All

I`v done the calc and I`v found that I need more primary to get the system to tune. OK so adding more primary C is not an option also there is no room to add an extra turn on to the primary, so I built a small inductor out of 14 turns of thick insulated copper wire about 3" dia in the centre is a soft iron core made up of ferrous rods.

This plus the primary coil give just over the required inductance.

What are peoples thoughts on this ? method and construction.

Cheers Mike"

Nothing wrong with using an extra inductor in the primary, but it will reduce the coupling. In this case the "soft iron core" will probably overheat (the extra coil is nothing much more than a small spark-excited induction heater coil) and the losses will certainly be excessive. Vary the number of turns but don't use an iron core.