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RE: DRSSTC, OLTC, OL-DRSSTC, M.I.C.,K.E.Y M.O.U.S.E. TC... Re: ALF: why not DRSSTC?

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Steve,

At 03:24 PM 9/30/2005, you wrote:


Good and rather accurate method of the msm,below
breakout,is the system using a plane wave antenna
array.


http://hot-streamer.com/temp/PlaneWave.pdf


I know about the plane wave antenna. The problem with it is how do you calibrate it to read absolute voltage instead of just a relative measurement?

The frequency response goes all the way down to like 16Hz. So you just "charge up" your coil from any known low frequency high voltage source (60 or 50Hz) like an NST or MOT. If the NST puts say 20kV peak on your coil, you just move the antenna around to get say 20mVpeak. It really is just that simple. It seems to get within 5% pretty easily. You can also resonate the coil from a signal generator and measure Q and stuff to get a known top voltage. However, just an old NST is really far far easier and works perfectly well... I use a 60Hz 40kV high voltage probe to check the NST voltage.

Of course, keep the antenna far enough back so it never can get hit (that would be a "bad" thing). The ~ 1 square foot bigger antenna really picks the signal up strong and solid from a distance!! I think it is best to use a point for streamer breakout that is directed on the opposite side of the coil from the antenna so the streamer does not mess the measurement up.


I never understood how Dr. Resonance's calibration method with the HV DC power supply was meant to work, since the plane wave antenna is basically a capacitive divider, and those don't respond to DC. Did he charge the toroid to a known DC voltage, allow it to arc to ground and look at the magnitude of the resulting step?

He "stepped" the voltage. DC is actually using the very first version I made ;-) But you charge the coil to say 50kV and suddenly sort it and go buy the step response.


I use a sort of "Ghetto" plane wave antenna composed of a metal disc stuck on the end of a 100:1 scope probe.

Probably not too bad really, but the plane wave antenna is like "real science" ;-))

BTW - I don't think it is super necessary to etch a pattern on the antenna unless you are going for 10MHz plus signals. Just a Flat chunk of PC board does real good too. I gave my old one to Gerry but I am not sure he has played with it yet.

Gerry also says:

Hey.... Maybe we can use it as a buffer amp in your planewave antenna to verify the low frequency performance (where the termination starts opening up below 150KHz).

My 50ohm HP33120A signal generator can do that into a 0.0015pF load too :o))) Trust me Gerry, it is flat ;-) You just take the output of the generator to a pop can right "near" the antenna and you can sweep around all you want. At say 100MHz, things get messy, but 200kHz is simple ;-)

Cheers,

        Terry



Steve Conner
http://www.scopeboy.com/