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Re: Variation of secondary Q
Original poster: "boris petkovic by way of Terry Fritz <twftesla-at-qwest-dot-net>" <petkovic7-at-yahoo-dot-com>
> >I have not heard back from Paul on this yet but
> here are some other ideas.
> >I could directly connect my 2.5pF 10Meg ohm probe
> (Tek5100) directly to the
> >top of the coil for a read out like this:
> >The scope could then save a data file like this:
> >The resonant frequency drops from 84.42 kHz to
> 82.15kHz so the probe loading
> >is very low (Those are darn good probes!! Like
> Pearson stuff, they too are
> >made out of pure money :-))). I imagine one could
> back calculate the small
> >probe loading right out.
> >However, assuming Vtop = Q x Vin we can just
> input 1 volts RMS and read
> >out the top voltage for a direct Q reading along
> with time and frequency and
> >just have all our data there without needing to do
> anything but push the
> >save button ;-)) (may have to check for frequency
> >That almost seems too easy :o)
> >If this is OK with Paul, it would be very easy to
> do. The scope can filter
> >it down and over sample like 512 times to get very
> high accuracy. But that
> >is probably over kill. I am not sure this would be
> 100% OK with Paul's
> >paper and all, but it should be close enough I
> would think.
> >I wonder if the Q variation is not so much the coil
> changing but the
> >surroundings changing with weather? The coil is
> far more stable for
> >temperature and humidity than the ground, walls,
> ceiling, etc. Just a
> >thought there.
> > Terry
Hi Malcolm ,Terry,
The fact is that Qs can change as type of ground plane
soil and other settups change.
Latest trades also suggest that phenomena of eddy
current losses in nearest primary turns carry away
Thus ,the change of secondary Q should be noticable in
msm with or without primary coil in place.
This especially holds true for very high Q
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