Re: Secondary Q

[Terry Fritz <twftesla-at-xxxxxxxxxx>]

Hi Kennan,

Disruptive coils have very low over all Q.  My big LTR's is about 2.48 as
shown in the graph at:

http://63.229.238.62/TeslaCoils/Misc/BigLtr-VvF.gif

This is how we can load up streamers and do other frequency altering things
and still get good output.

I think the discussion of Q really comes down to losses in disruptive
coils.  Since I used Sonotube, my streamer length may be about 5% less than
if I had used PVC.  A surprising amount of power is going into heating the
cardboard.  As you note, our voltage amplification is by impedance
transformation rather than pure resonant ring up.

Of course, 5% is not a super big deal but the loss is surprising. In a
humid place, it may become a real problem.  In a CW coil, heating could
become a real issue since the tube could get hot enough to burn if you are
really pushing a lot of power into the system.  Q is far more important in
the CW case.

BTW - Tesla had some nice CW coils too in teh 1900's that ran off high
frequency alternators.  However, unlike our disruptive coils today, he
would not recognize most of the parts of today's solid state machines.
Tubes were the "modern" thing in his time so he would not have a problem
with that  ;-))

Cheers,

	Terry


At 01:30 PM 11/4/2000 -0800, you wrote:
>There's been a bit of discussion of secondary Q recently that leads me to
>ask how all you 19th-cy. spark-gap types (the vast majority!) manage to
>utilize decent Q at all:  Your tuning is imprecise due to difficulty in
>getting primary resonance to match that of the secondary; and
>also--certainly when using a secondary with a Q as high as 80-100, which
>I've measured for mine--because the secondary's resonant frequency is not
>only "hard to find" but also it is going to shift markedly whenever a
>conducting surface gets anywhere near it.  You've got two resonant
>circuits searching for each other, so to speak, with not a whole lot of
>continuing success, I should think.  
>
>I'm aware of the assertion that the energy stored in the primary
>capacitor gets put into the secondary capacitance, less that lost due to
>gap loss and to primary:secondary coupling inefficiency.  So if the
>capacitance ratio is 100:1 and you start out with 10KV on the primary one
>then theoretically you end up with a respectable voltage in the
>secondary's capacitance prior to the zap.  But where, then, does
>resonance come into it, and how are you going to gain, particularly, by
>having a high-Q secondary?
>
>Perhaps I'm too much of a purist but I stick with my s.s. system in which
>there's only one resonant item, the secondary, and that item itself is
>the resonant element in a feedback primary-driving oscillator circuit. 
>Always spot-on, resonance-wise, cycle by cycle.  So with my scheme, the
>higher the Q the better since higher Q facilitates higher voltage
>build-up prior to the spark.  
>
>Comments?
>
>Ken Herrick
>________________________________________________________________
>YOU'RE PAYING TOO MUCH FOR THE INTERNET!
>Juno now offers FREE Internet Access!
>Try it today - there's no risk!  For your FREE software, visit:
>http://dl.www.juno-dot-com/get/tagj.
>