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On Sun, 29 Apr 2007 14:30:29 -0500, "amdx" wrote:
Capacitance does not bring loss. I'm not ready to give on that yet, but I could be convinced. It seems I could add capacitors across turns of a coil and increase circulating currents that would show as a lower Q. But I haven't built a coil to test this. Hi Mike, This is then a characteristic of the Capacitor called D (dissipation). Any increase in current tied to loss immediately goes to the bottom line of resistance - it is a square law relationship, after all. Loss ALWAYS resides in Resistance and nothing else. I agree, X/R=Q Lower Q means more loss. (let's not get into radiation resistance right now) Why not? Small loops suffer by comparison, and multi-turn loops even more so. Proximity effect could cause all of the additional losses. Or it might just be part of the additional losses. For wire separations beyond 3 or 4 wire diameters, the increase in skin effect is small. It might be noted that interwinding Capacitance also falls. Why is it that when you get near self resonance of a coil the Q gets lower? Note; to help clearify my question, ( as you get nearer and nearer resonance the capacitor you are using to tune the inductor is getting smaller and smaller, and closer to equalling the self capacitance of the inductor) Again, the answer must reside in Resistance. There are many characteristics (wavelength, solenoid diameter, length, pitch, wire gauge, self-capacitance, distributed capacitance, balance, connections, earth proximity, radiation resistance) being juggled with small Loop antennas and some (even many) choices that can be made to resonate the antenna do not lead to an efficient solution. 73's Richard Clark, KB7QHC |
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