From: "Terrell W. Fritz"
Date: Sat, 02 Sep 2000 15:20:12 -0600
Subject: Re: [TSSP] Mystery of the missing loss
Hi Paul, Today I raised the secondary coil up 12.5 inches with a holo styrofoam box. With the bare coil. the Q was 61.7 and the Q was 97.3 with the toroid. This compares to Q's of 57.7 and 80.9 with the coil on the continuous gound plane. So moving the coil further away from the eddy currents, or whatever, of the plane did not have a "dramatic" effect on Q... In retrospect, I think having the high voltage end of the coil near the ground plane gave a lower loss secondary capacitance which was responsible for the high Q reading. The coil's Q seems to vary much depending on hard to control (at least in one's basment) factors. Perhaps if some "standard" evironment or setup could be extablished that would go well with the math models, we could take Q reading more consistently. I fear the best expermenters trying to reproduce the same Q measurements could get fairly large errors depending on a number of little factors. I would guess that +-20% accuracy is all that could be expected. Cheers, Terry At 09:15 PM 9/1/00 -0600, you wrote: >Hi Paul, > >I patched up the ground plane. It is now solid and NON-SPLIT again. > >I decided to violate the "pristine" ground plane area and get right on in >there with some equipment to see what was what. So with a load of >equipment and wires in there the numbers shifted but I was able to get some >Q data with a "rough" ground plane. > >Bare Coil >f1 = 148.3kHz Q = 57.7 >f3 = 347.87kHz Q = 33.3 >f5 = 513.76kHz Q = 20.3 > >45 inch Torroid >f1 = 97.93kHz Q = 80.9 >f3 = 322kHz Q = 36.6 >f5 = 491.2kHz Q = 23.8 > >Then I tried to measure the coils AC resistance with a 41pF fixed super >high Q ATC ceramic cap in series with the coil, generator, and a 50 ohm RF >resistor. Even though the Q of the ceramic cap is "so high it can't be >measured", the Q of the circuit was only 14.1! I played with it awhile and >discovered that if I put the coil up on a plastic bucket, the Q shot up to 75! > >I was powering the coil upside down so the high voltage end would have been >near the ground plane. That probably had a big effect. But I was thinking >the fixed cap would pretty much keep the fields in check. > >So I am know wondering if the very close ground plan is have a >"devastating" effect on the coil's Q. I was thinking of looking at the Q >with the coil and terminal on the bucket about a foot away from the plan >and seeing what happens. This is yet to be done but it appears to be in >important thing to look at... > >For reference, two pictures of the "mess" are at: > >http://63.225.104.218/test/TeslaCoils/Misc/PaulNich/P9010007.jpg >http://63.225.104.218/test/TeslaCoils/Misc/PaulNich/P9010009.jpg > >BTW - This site was down for the last 48 hours but should be fixed now. > >Cheers, > > Terry > > >
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.