From: "Terrell W. Fritz"
Date: Tue, 08 Oct 2002 12:44:13 -0600
Subject: Re: [TSSP] Curiouser and curiouser!
Hi Paul,
At 08:29 AM 10/8/2002 +0100, you wrote:
>
>Terry,
>
>Your Q factors have just about doubled, comparing now with
>Sept 14th,
>
> Sep 14 Oct 7
> f1 37.801 kHz 37.229 kHz
> f3 113.550 kHz 113.864 kHz
> f5 171.773 kHz 172.448 kHz
>
> q1 42.94 84.19
> q3 19.45 46.26
> q5 14.32 34.37
>
>Not much change to the frequencies, f1 down a percent an the
>other two up 0.3% and 0.4%. Greater Q improvement for the
>higher modes, so whatever the origin of the loss that you've
>lost, it was either coupled reactively to the coil, or
>concentrated in one region.
Nothing should have changed from before. The coil was just mostly sitting.
Only time was a factor as far as I know.
>What a difference being indoors
>for three weeks makes. Have you altered ground arrangements?
>I guess not. I recall similar variations with your big LTR
>coil.
Sonotube tube is pretty waxy, maybe the water just takes a long time to dry out
of it.
>
>When you've built your plastic cored high Q replacement,
>see if you can ping it with and without a length of sonotube
>inserted down the middle. I guess you'd need two lengths
>of sonotube, one bone dry, the other allow to become damp.
>
>That would confirm once and for all the suspicion about
>sonotube.
I don't need a plastic one now ;-) This one seem to work pretty well (now). I
can play with another piece of sonotube inside it and such. I'll see if I can
figure anything out.
>
>I don't know what's happening to your 3/4 wave mode on
>the running coil. It seems to be breaking up and tcma
>is making a hash of it. Why isn't the 1/4 wave mode split?
>Did you capture the ping starting after the quench? Or is
>your primary desperately out of tune? Maybe the f3 of
>the sec is being modulated by alternative f1 half cycles,
>with the IGBT's switching on and off. 114kHz when the IGBT
>is off, and 120 kHz when the IGBT is on (or maybe the other
>way?), the modulation occuring due to the pri-sec cap and
>the effective Lsec being altered.
I think I did the capture and all just right. The running coil is very stable
and the waveform "looks fine" to the eye. I have the data files... Ok, I'll
try and find what I did with the disk and post the data... I think I took the
disk to work... I'll find it...
>
>You could test for that by pinging with the pinger and
>looking for the change in f3 as you manually make/break
>the primary loop. If such is the case, why aren't f5
>and f7 upset? Most curious.
I wonder if it could be a scope alisasing thing or jitter or something...
Hmmmm..
>
>Seeing that the 3/4 wave overtone of your loaded secondary
>is only a little above the 3rd harmonic of the 1/4 wave,
>perhaps the rectification in the primary circuit is
>generating enough 3rd harmonic of f1 to upset tcma. But
>I'd have expected something at 111.4 kHz. Still, it would
>explain why the other modes aren't affected.
>
>(from pn2511, eq 9.8)
>
>R = 2 * pi * F * Lee/Q = 2 * pi * 37229 * 0.416/84.2
> = 1200 ohms.
>
>That's the coil resistance referred to the base terminal,
>ie the input R.
I still get about 600 ohms... So the Q has changed by a factor of two and the
resistance "seems off" by a factor of two... Of course, that suggests I have
messed something up somewhere ;-) But I sure don't know what could go
wrong... I thought the Q equation and the models "used to" work right... I
try to figure the discrepancy out... The difference is like night and day so
it should be obvious...
>
>tssp predicts 78 for your q1, based on the estimated AC
>resistance of the winding plus an estimate of proximity loss
>from Medhurst tables. Thus I wouldn't expect your Q to rise
>much more, ie your sonotube must be pretty well dried out by
>now.
I have a heat lamp so I may try to "carefully" warm it up.
So, just when I thought this was all figured out, everything went and
changed... "Q" and "SonoTube" seem to be a wild combination!! But if it is
just really sensitive to water absorbed in the tube, that can be fixed...
Cheers,
Terry
>--
>Paul Nicholson
>--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.