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Re: TC vs MAG
From: richard hull[SMTP:rhull-at-richmond.infi-dot-net]
Sent: Monday, August 25, 1997 2:16 PM
To: Tesla List
Subject: Re: TC vs MAG
At 12:36 AM 8/25/97 -0500, you wrote:
>
>From: bmack[SMTP:bmack-at-frontiernet-dot-net]
>Sent: Sunday, August 24, 1997 10:37 PM
>To: tesla list
>Subject: TC vs MAG
>
>hello all
>
>I've been reading references here and there on the list to
>magnifiers and secondary windings of TC's.
>
>To the best of my understanding, the difference between the
>mag and the TC is that the mag uses tight HF transformer coupling
>(as tight as air core gets-that is) and uses an additional quarter wave
>resonator in series with the Hf transformer secondary. This additional
>resonator should have as little magnetic coupling as possible as to
>avoid damping. Right so far?
>
>My questions are:
>
>1) Is the mag secondary quarter wave resonant, or is the turns ratio
>the main issue here?
.........................
I have been maggey building longer than most and have thought and read long
and deep. Needless to say, experimented a hell of a lot. I would say both
have validity and will work, but..... Tesla sort of demanded two quarter
wave units tuned to the same frequency. I have had only moderate success
with this approach and feel EITHER a super fine impedance match is needed
and that the airbourn transmission line is a major chuck of the exercise for
the same frequency system, OR The impedance of the driver needs to be a
least an order of magnitude lower than the base Z of the resonator.
The key to the Turns ratio bit is the realization that there will be
virtually zip resonant rise in the loaded driver system. Thus, Turns ratio
amplification is not a back hook to hang one's hat on. Tesla even mentions
this at one point in the CSN! R. Hull
..........................................................
>
>2) If it is quarter wave, the sum length is half wave which should
>give poor results. Is there some phase abberation that makes this
>work?
..............................................
If the system is looked at as a lumped system then the half wave bit would
be correct (theoretically) along with poor performance. If lumped, then the
tune of the primary would be the quarter wave total of the secondary and
primary. I think this works very well provided the inducatnce ratio of the
driver secondary and the extra coil are at least an order of magnitude
apart. Tesla also mentions this in the CSN.
.................................................
>
>3) Some coilers don't get seem to get too fussy about the actual
>wire length used, rather they use a "magic number" of 900 turns.
>Maybe I'm too theoretical, but I ALWAYS calculate the wire length
>to get a "ballpark" idea of free resonance, THEN go for optimal
>aspect ratio. I would like your opinions on this.
........................................................
Wire length is always irrelevant in any Tesla system!!!
I know dammit you want reasons!!!! The top load is so very critical and
must be grossly oversized for best operation. It would forever be
impossible to even slightly approximate some sort of wavelength of helical
wound wire to a mime of theoretical frequency of operation. The real
builders have known this for many, many years. Only the theoretical newbees
or radio engineers tend to cling to this nether world dream. Likewise,
drowning coilers want something to cling to, and tout the 900 turn, 800
turn, or whatever is politically correct now, statements. Both of the above
are a real crock and limit real advances. Classic, static thinking based on
classroom theory, on the one hand, and rules of thumb on the other. R. Hull
.......................................
>
>4) In some low power table tops I've built, it was noted that the
>resonant freqency was very sensitive to the actual wire length.
>In fact the secondary could be in two or more sections separated
>by about a foot (didn't try longer) and still maintained a frequency
>realtionship to pure length!
>These models used small top capacitances.
>Thus my confusion about the magnifier concept.
>
>Thanks in advance,
>
>Jim M
>
>Jim,
Good! You are thinking! The pure length does always and forever relate to
the frequency of resonance on a fixed form by some factor (K). This
relationship shifts about constantly based on a number of highly variable
parameters relating to altered capacitance of the series resonant circuit,
from interturn capacitance-(tight or space wound), from terminal
capacitance, elevation, length of transmission line (in the case of your
broken in half resonator), etc., etc.
Also, the inductance is variable based again on space winding vs tigh
winding. Wire gauge to a lesser degree can affect this. This (K) is not
easy to pin down if a number of these parameters are monkeyed with. The
solution for K becomes a highly complex function in designing any coil from
scratch.
Richard Hull,TCBOR
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