From: Paul
Date: Thu, 12 Jul 2001 07:52:48 +0100
Subject: Re: [TSSP] Thor base current measured
Marco Denicolai wrote: > > What would you do with a grid-dip meter? > It's a thing that radio hams use for looking at resonant circuits. Its just an RF oscillator which can be tuned over a wide range. Fitted with a probe and a meter, you put the probe near a tuned circuit and sweep the dial until the meter 'dips' (traditionally a valve oscillator and the 'dip' is the DC grid bias dropping when the tuned circuit absorbes power from the oscillator. Has around 10^6 uses around the radio shack. In this case you can just set it to 800kHz and 'sniff' around the TC until you find the part of the circuit that is ringing. For example, http://hem.passagen.se/sm0vpo/use/gdo.htm I ran the model of Thor last night, and I now get: Overall view:- http://www.abelian.demon.co.uk/tssp/md110701/md3.gif First 20uS:- http://www.abelian.demon.co.uk/tssp/md110701/md4.gif If the model is working at all, we should get a good match in this first part of the waveform, because no time has elapsed to cause phase errors or decay errors due to unknown Q. The mode amplitudes are just those resulting from the initial decomposition. First notch:- http://www.abelian.demon.co.uk/tssp/md110701/md5.gif As you can see, we now have roughly the right phase of mode 3 in this notch, so this is very encouraging. Second notch:- http://www.abelian.demon.co.uk/tssp/md110701/md6.gif By this point, the phase of the fundamental modes has started to drift, which shows that the precision model cannot be relied upon for detail beyond say, the first notch. Fortunately, that covers the breakout that we want to study. On the whole, the measured amplitude seems to be a little higher than predicted, but then maybe you had slightly more than 14kV on the primary cap? I'll do a more thorough write-up of this at the weekend. Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.