Re: Resonance The hook up

Hi Philip, all

You wrote
" I used my scope and funtion gen. Fed sine wave intp base of coil and
 hooked scope to other end of coil. I increased frequency until wave form
 grew in voltage. That I assumed was the resonance point. Is this wrong?"

YesNo. The idea was okay. However your setup is incorrect. First of all, you
do not want to "connect" your scope to the coil. Doing so will load it down
(and give you the results you saw: 234kHz vs. ~400khz should be). Try doing it
this way:

a.) Build yourself a pickup antenne. A 50 cm piece of wire is fine. Connect
this wire to a 50ohm coax cable (to the hot wire). The ground wire stays open.
Place this pickup about 1 yard away from your coil. I justed taped mine to the
ceiling. Worked great!! If you do tape it to the ceiling, be sure to stay away
from electrical wiring in/above the ceiling, as this will give you false
results. Connect a 50 ohm "trap" across the scopes input to prevent false
readings as a further measure and use BNC connectors throughout, too.

b.) Place your secondary (no primary, tank circuit, etc.) coil on something to
raise it off the floor. Also keep the area (at least a 3-4ft circle) around
your coil clear of everything (esp. metal parts). You will be amazed as to how
sensitive your coil is to anything near it. Esp. if it is a high Q coil.
During my Q-Testing coming any nearer than about 2 ft to the coil let the
scope trace (amplitude) fall flat on its face. Try it on yours by just placing
your hand near the coil, once you have found FRes and you will see what I

c.) Connect the bottom of your coil to the hot wire of the signal generator
via a 50 ohm coax cable. The sig gen ground stays disconnect, too.
d.) Adjust your sig gen (by trying) until you get roughly near FRes. You will
notice a large jump in output voltage on your scope. Now readjust your scopes
V/div and time base until you have a single waveform on the screen. The
amplitude should be slightly below the last divisions on your screen. This
step isn´t really necessary, but it lets you see changes easier and "back
calculating" the FRes from the scope picture is easier, too.

e.) Very slowly increase the frequency until you have max amplitude. If you
have a f-counter you can read it directly, otherwise you will have to "read
it" from the scope.

f.) Now you can add toploads and see what they do to your FRes.

The above setup works for the secondary coil ONLY. If you are interested in
finding the primary´s FRes, let me know. 

Really measuring your FRes (yeah, I´m a "hands on" guy) will aid you in tuning
your coil, because you will be closer to the sweet point, even before you
start sparking. I.e. it is easier and quicker knowing you are in the "range"
than to wildly start at some tap point on your primary and having to go up and
down several turns until you hit it on the nose. :o)

Hope this will get you more accurate results.

Coiler greets from germany,