Re: Recycled: Measuring Coupling Coefficients

From: 	Greg Leyh[SMTP:lod-at-pacbell-dot-net]
Sent: 	Wednesday, December 03, 1997 4:37 AM
To: 	Tesla List
Subject: 	Re: Recycled: Measuring Coupling Coefficients

Thomas McGahee wrote:

> John,
> Terry originally thought the same as you about the operating
> frequency, but found that in fact the method is not dependent
> on frequency. In fact, as the title of one of his posts pointed
> out, this method is perhaps the best for most coilers as it does
> not require very much in the way of test equipment, and yet yields
> answers at least 1% accurate if you use a heating element or
> high power resistor as the current limiting element (as opposed
> to a light bulb, which is non-linear and introduces a bit of
> error at 60 Hz).
> Greg Leyh uses a variation on this method, where he applies 120
> VAC directly to the SECONDARY and then measures the voltage at the
> primary and the current at the powered secondary. It is always
> useful to have information on several different ways to do things.
> Then use the method that works best based on the equipment you
> have at hand.
> Always exercise caution when dealing with the 120 VAC power
> lines!

Actually, for the new coil I apply a 277VAC excitation voltage
directly across the secondary winding from the 277/480V feeder,
since the reactance of the sec winding is about 50 ohms at 60Hz.
The self-heating of the winding is negligible.

The msmt is more accurate at higher signal levels in this case,
as the secondary intercepts a noticable amount of RF energy from
nearby Sutro tower.  In fact, a small speaker in series with a 
signal diode is all that is needed to listen to the local AM 
radio stations pouring out of the secondary!