Re: Please Help! Trying to tune the primary coil (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sun, 24 Dec 2006 12:09:42 -0500
From: Slurp812 <slurp812@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Please Help! Trying to tune the primary coil (fwd)

I am a newbie here, and haven't even finished my first coil yet, so this may
not be 100% correct. Just connect the MMC, and the primary together (short
the spark gap) and remove the power supply and Terry filter. So basically
you would have the primary, and the cap in parallel. then inject a signal
across both of them, and scope across the same points. Sweep the signal freq
until you get the highest voltage rise. Tune it until the rise is at the
target freq, or a tad LOWER. I just wanted to say that your construction
looks great so far, very excellent work. The metallic looking legs bother
me. Are those metal?





On 12/24/06, Tesla list <tesla@xxxxxxxxxx> wrote:
>
> Moderated and approved by: Gerry Reynolds <greynolds@xxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Sun, 24 Dec 2006 20:34:19 +0800
> From: westland <westland@xxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Please Help!  Trying to tune the primary coil
>
> Hi All:
>
> I've gotten to the stage where I need to tune my primary tap point, and
> I've run into a problem in trying to figure out how to wire up the
> primary coil to find the resonant frequency.    I initially pulled the
> secondary, put it on a plastic base, injected RF from my signal
> generator, and read the response off of my oscilloscope with a small
> antenna set as the input feed.  This worked well, and gave me a resonant
> frequency of 205KHz for a 4" x 22" coil with a 5x16 toroid topload.
> Here are pictures of the setup (sorry for the fuzzy initial picture)
>
> Secondary tuning setup Antenna:
> http://www.flickr.com/photos/51115445@N00/331719458/
>
> Secondary base (so it doesn't fall over when measuring):
> http://www.flickr.com/photos/51115445@N00/331719464/
>
> Secondary tuning setup:
> http://www.flickr.com/photos/51115445@N00/331719457/
>
> ********
>
> So far so good.  So I hooked up the primary and the MMC (which I had
> tapped for 10.2 nF... see pic).  But I couldn't figure out how to wire
> up the tank circuit so that I could get a reading off my oscilloscope of
> the response to the injected RF signal (I tried several configurations,
> plumbing the Internet for sources, but couldn't get anything to work ...
> my voltage rises were all in the over 1 MHz area).
>
> I decided to compute from readings off my RLC meter, and found that I
> needed to tap near the end of my 14th winding (with the 10.2 nF cap) to
> get a resonance of 205K.  But even with this setup, I couldn't get the
> scope to give me any readings at all in the low kilohertz rang.  Here
> are more pictures of the setup.  I also tried to test the complete coil,
> but that didn't work either.
>
> Measuring impedance of MMC:
> http://www.flickr.com/photos/51115445@N00/331719460/
>
> Trying to measure resonance of primary coil:
> http://www.flickr.com/photos/51115445@N00/331719462/
>
> Measurements for complete Tesla coil:
> http://www.flickr.com/photos/51115445@N00/331719463/
>
>
>
> Can anyone give me advice on where I am making my mistakes here.  From the
> descriptions I've read on the Internet, tuning the primary should be
> straightforward (but no one tells you how to wire up the test setup).  You
> are looking for two peaks with a valley at the secondary resonance
> (indicating the secondary is drawing power away from the primary circuit)
>
> Thanks in advance for the help
>
> Chris Westland
>
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> --
> ____________________________________________________
>
> J. Christopher Westland, PhD CPA
> Professor, ISMT, University of Science & Technology, HK Clearwater
> Bay,Kowloon, Hong Kong
> Tel: 852 2358 7643
> Fax: 852 2358 2421
> Mob: 852 9528 1745
> URL: ihome.ust.hk/~westland
> Mobile e-mail: chris.westland@xxxxxxxxxxxx
>
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