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Re: Hello,
At 10:38 PM 1/24/97 -0700, you wrote:
>> Subject: Re:Hello,
>
>Subscriber: bert.hickman-at-aquila-dot-com Fri Jan 24 22:37:54 1997
>Date: Fri, 24 Jan 1997 22:18:29 -0800
>From: Bert Hickman <bert.hickman-at-aquila-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: Hello,
>
>Tesla List wrote:
>>
>> Subscriber: c604313-at-showme.missouri.edu Thu Jan 23 22:34:51 1997
>> Date: Thu, 23 Jan 1997 16:01:24 -0600 (CST)
>> From: c604313-at-showme.missouri.edu
>> To: Tesla List <tesla-at-poodle.pupman-dot-com>
>> Cc: Tesla-list-subscribers-at-poodle.pupman-dot-com
>> Subject: Re:Hello,
>>
>> Hello Tesla builders,
>> Hi, my name is Bert Schumann from Columbia Mo. This is my first e-mail
>> to the group. I'm glad a group like this exists and that it wasn't hard
>> to find! (Are there any other coilers in the mid missouri area???)
>> I've built several coils over the past 4 years, just small ones (300
>> watts). And am in the process of trying to get a larger one up and running
>> (700 watts)., but low and behold I seem to have a knack for blowing out
>> neon xformers (at least I didn't blow out an entire power station like
>> Tesla did at Colorado Springs!!)
>> Any way, I was woundering what would be the best way to test for
>> resonant frequency in the secondary (Toriod included) if one had a
>> variable function generator and o'scope available to use? I hear it is not
>> such a good set up to just string a wire a couple of turns around the
>> secondary and then hook it across the function generator with the o'scope
>> placed on both the top and bottom of the secondary. The o'scope will
>> actually change the resanant frequency some, but is this effect
>> negligable? Is there a better way to test for Sec. Res. freq?
>> And what about the primary? I was just planing on hooking all
>> primary parts together in series with the function generator and o'scope
>> (minus the sparkgap and xformer of course and probably throw in a
>> resister in order to keep the function generator from strainin'.) I would
>> then adjust the function generators frequency in order to find its max
>> through put. Is this a satisfactory set up?
>> Thanks,
>> --Bert S.
>
>Bert,
>
>Now the list has at least 3 Berts! The easiest way to test the resonant
>frequency is to leave the secondary/toroid in-place inside the primary,
>disconnect the earth ground from the bottom of the coil, and connect a
>sine-wave signal generator through a pair of high-brightness LEDS (back-
>to-back) to the base of the secondary:
>
>
> LED's
> from |--|<----|
> signal -------| |------ to base of secondary/toroid
> gen. |--->|---|
>
>
>The signal generator should be capable of driving at least 4 V
>Peak-to-peak. Slowly increase the frequency until you find the frequency
>that gives you the most current (i.e., the brightest LED setting). This
>will be the natural resonant frequency of the secondary/toroid pair
>(Fo).
>
>You can do a similar thing with the primary, only this time REMOVE the
>secondary completely and put it into another room. Next, short the
>sparkgap and connect the signal generator, through the LED's, across the
>tank capacitor (power off, of course!). With the spark gap shorted,
>you'll have the primary inductance in parallel with your tank cap. Now
>carefully adjust the signal generator to find the point of minimum
>current ("anti-resonance"). Adjust the coil tap until this is the same,
>or slightly lower than, the secondary/toroid center frequency above.
>
>Just for grins, since you've come this far, let's measure the coupling
>coefficient (i.e., the portion of magnetic field lines that are common
>to BOTH the primary and secondary). Leaving your signal generator
>connected as before to the primary with the sparkgap shorted out, put
>the secondary/toroid back into the center of the primary and connect the
>RF earth-ground to the base of the secondary coil. Now adjust the signal
>generator to measure the two points of lowest current - these should be
>approximately centered around the previous primary and secondary
>frequency. The greater the seperation between the lower and upper
>"sideband" frequencies, the greater the degree of magnetic coupling
>between the primary and secondary coil. Assume you measure sideband
>frequencies Flow and Fhigh. The coupling coefficient, "k", can now be
>found as:
>
> k = (Fhigh - Flow)/Fo
>
>Certain values of "k" will tend to cause better operation, with 0.153,
>0.18 or 0.22 being a few of the "magic" values.
>
>Hope this helps!
>
>Safe coilin' to ya', Bert!
>
>-- Bert --
>
>
Bert H: (from Bert P)
This was a very timely posting, as I am about to measure the K on my new
system. You've saved me the task of searching through my archived files for
the exact method.
Thanks!
Bert Pool
nikki-at-fastlane-dot-net