From: Paul
Date: Sat, 23 Jun 2001 08:52:39 +0100
Subject: Re: [TSSP] Short Coil Experiments
Concerning the 38cm diam, h/d=1/15, coil, I wrote: > > (Kurt, the f7 measurement is suspicious - I'd expect something > > around 980 kHz. I see you flagged it as questionable.) Kurt Schraner wrote: > This measurement was nothing more than a just distinguishable change of > appearence of the scope trace (very small amplitude), at roughly the > indicated frequency. It should be discarded; better I was not even > including it in the results-table! OK, I appreciate the difficulty with this coil. The Q is very low, presumably due to the dielectric material loss, so the higher modes will be heavily damped and with a high base impedance. > If the Generator-Z was really low, the measured Q should not be > too far away from reality. The effective series resistance of this coil is so high that switching between a 50 ohm source and a zero ohm source would only make 5% or 10% difference to the Q. There's something about paper/cardboard/sonotube coils that make them very lossy indeed. Maybe some additive put in to bind the material together? I'm still looking at the strange results for Sk-5cm, as mentioned in the previous email on this thread. More later... Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.