Hello All, To successfully tune all the coils at slightly differing frequencies theres a 'trick' which you may not know of. The trick is simple to explain but not so in the doing. The 3 coils in this case need to be at EXACT NULL relative to each other. Diagrammatically they appear as the three primary colours arranged to show central white and secondary intermixing twins....Sound familiar? Using 2 to start. When the coils overlap the outside sends positive EMF induction and the inner sends negative EMF. At 1 EXTREMELY SENSITIVE and PRECISE point they totally (theoretically) cancel out. In practise the coils have to be interleaved and this is almost impossible. 2 separate coils can be positioned first and fixed at the lowest point by resonating 1 (TX coil) and sensitive scope on the other (RX coil) for best null. When done, test 'em on 2 differing freqs. If you use a small local loop to scope input you should see intermixed freq on ssslllooowww timebase like AM transmission. You can have very small freq differences between the coils this way and they dont always lock BUT the oscillator has a lot to do with this...just enough gain to sustain as pure a sine as poss WILL help lots. The 3rd coil is a basxxxxd to align, it WILL change the freqs of the others, it WILL upset the perfected balance setup but can be done by attaining the original freqs as a starting point then scope this coil for null. The freqs of the other 2 should be as originally setup if the 3rd is at perfect null. There is a massive phase shift with the smallest of offset from perfect null, I have a GEB discriminator 1985 thats never been beat based on this.  The first 2 are quite simple to setup but the 3rd .....try it youll see.... Hope this helps Steve.
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Topic: Tuning multiple coils in close proximity (Read 18262 times)
