Quote:
Originally Posted by FrancoItaly
Hi Esteban
I remember an old instrument, a Grid-dip-meter, used in order to determine the resonance frequency of a tuned coil, without some electric contact. the tuned coil it absorbed some very little energy from tube oscillator and it caused a change in some parameters of the instrument. This was possible for the very high impedance of the input grid tube. I think that a coil tuned on a high armonic of a oscillator acts as a sort of frequency converter, that's it can translate in a lower frequency any change of the high frequency. For Morgan I am a lot interested of Damasio'book but I don't think that it's possible for me to obtain a English translation, however I thank you.
Best Regards
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I think that the device used is not a dipmeter. A dipmeter consist in an oscillator. From Wikipedia:
Grid dip oscillator (
GDO), also called
grid dip meter,
dip meter,
dipmeter, or just
dipper, is a
measuring instrument to measure
resonant frequency of
radio frequency circuits. It measures the amount of absorption of a
high frequency inductively coupled magnetic field by nearby objects. It is an
oscillator whose output energy changes in the vicinity of a resonant circuit which is tuned to the frequency the oscillator generates; somewhat similar to an acoustic tone becoming louder when generated in the vicinity of a resonant cavity or a string tuned to the same frequency. At the heart of the instrument is a tunable
LC circuit with a
coil that serves as a loose inductive coupling to the measured LC
resonant circuit. Resonance is indicated by a dip in the meter indicator on the device, usually based on a
microammeter.