I hope that Tom, Phil and others are including Jim on their replies. He
sounds like a darn good resourse for some of our more lively discussions!
73....Carl KM1H
--------- Begin forwarded message ----------
From: vanputten@terman.physics.hope.edu
To: ham-tech@majordomo.netcom.com
Subject: EXPERIMENTAL RESULTS ON SHORTED TURNS
To: <amps@contesting.com>
Date: Thu, 24 Apr 1997 22:55:20 -0400
Message-ID: <97042422551990@terman.physics.hope.edu>
While waiting for opinions on shorting unused turns of a tapped
coil, I made a couple of measurements on a 10 micro Henry rotary
inductor. I set the inductance to 5 micro Henries and measured
the Q of the coil when it was resonanted with a 218 pF capacitor.
I drove the parallel circuit through a 1 Meg resistor and
measured the voltage across the circuit with a 10 Meg scope
probe. I calculated the Q as the resonant frequency divided by
the width of the response at 3 db down.
The results:
Open unused turns: F=4.8236 MHz, Q = 122
Shorted turns: F=5.2293 MHz, Q = 99
Not only did the Q decrease by about 20% but the effective
inductance also decresed by about 20%. Unfortunately I do not
have an coil of 5 micro Henries and the same construction to test
the Q with no unused turns.
Jim van Putten, Professor vanputten@physics.hope.edu
Department of Physics and Engineering PHONE: 616-395-7513
PO Box 9000 FAX: 616-395-7123
Hope College W8QT
Holland, MI 49422-9000
--------- End forwarded message ----------
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