From: Paul
Date: Tue, 05 Jun 2001 22:45:48 +0100
Subject: Re: [TSSP] Interesting article on Medhurst, Wheeler, modeling,etc.
Finn Hammer wrote: > I took this to mean that too few measure, and that there > is a lack of measurements on short coils, so I wound a 500 > turns coil, 160 mm in diametre and 146 mm long. It measures > 29.4mH on my handheld LCR meter. Thanks Finn. The h/d=0.91 is just a very nice size for this kind of test. Well into the region where Cint begins to be very prominent, and therefore just the right choice! I'd like to take a real close look at this coil. Do you have any sort of ground plane beneath it? A foil sheet perhaps? And can you let me know the wire gauge? > Sine generator to base of coil, sitting one metre up from > the floor on a 160 mm sewer pipe (pvc), scope probe dangling > 1/2 meter from the coil, with a cliplead as an antenna clipped > to the tip of the probe. I was close to the coil too, about one > meter, but long enough to not make a difference if I moved > around. OK. What's the output impedance of the generator? How does it connect to the base - coax? Where the does the generator get earthed? Shouldn't be too critical since we're not interested in the Q factor. We just need to make sure that there is a well defined ground surface dominating the area around the coil, and that the signal ground of the generator connects directly to this through the coax screen. > Frequences at which the scope trace roze high: > 340 kHz (measured with fluke 87 as counter, > it will not measure beyond 650kHz) > 725 kHz > 1100 kHz > 1450 kHz How were the higher frequencies measured, from the generator dial? > Sorry guys, perhaps there is a description of a good measurement > procedure I could follow? We'll figure it out as we go along! > I`m here to learn, and to help provide some of that experimental > evidence. Just what we need Finn, and you've come up with just the right coil I think. Looking forward to working with it - its going to be an interesting one. You'd better let us know what instruments you have at your end. Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.