Sunday, April 7, 2013

BFO for measurig inductance

I use this ckt very extensively for knowing the resonance of my tuned IF stages (4mhz, 10 mhz), band pass filters , oscillator tank ckts.

As such it does not meaure inductance directly. For measuring you have to do the calculations. Connect Inductor-L and put 100 pf capacitor across it to make a tuned ckt. Now, read the freq in the counter. with the help of formula calculate the inductance.
Please note you will be not able to work out the RFC values by this as it likes only High-Q inductance !

I use this to circuit to tune the tank (L and C) for a given freq. when either L or C is variable or both variable , change them to get the desired freq in the counter. remove your tank (L and C) from the osc and put it in your IF stage or oscillator stage, bandpass filter and you are on the spot.

This little ckt has proved itself over the time. Use of styroflex and polyster capacitor in this oscillator is a good thing.  I use 12 volt regulated dc.

Years ago i used when i did not have frequency counter, with help of analogue communications receiver ( no digital freq readout) and other xtal marker used to put the tanks of 4 mhz IF into resonance...

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