Re: raduino crystal question

Gordon Gibby
 

Crystals are specified by their manufacturer to oscillate to correct frequency when placed in a circuit that has a certain amount of parallel capacitance, which is a property of the circuit, not the capacitance per se of the crystal

If you need a few extra picofarads of capacitance and your circuit to meet the manufacturers requirement, that is easily added with a small capacitor.  

The reason that the bitx series tends to oscillate  just a little bit higher than where it should’ve, is because there apparently isn’t enough capacitance in parallel— which makes the crystal oscillator be a little higher than expected 

You can easily fix that in the source code of the software by just changing the designated frequency of the Crystal to match where it actually oscillates, and then all of your adjustments should be simple from then on     A good communications receiver will allow you to measure the actual oscillation frequency.  Dip a  wire near the raduino and you’ll pick up a  signal

Even easier is to command the read you a note to go to the specified frequency of the Crystal, and then measure the amplified output!   That’s a very loud signal!

Add 10-20 picofarads in parallel with the capacitor and you may find that you get it exactly on frequency without doing any software at all

These are wonderful things to learn in 
ham radio


On Aug 23, 2019, at 00:09, "ashok.das81@..." <ashok.das81@...> wrote:

Thanks KE7ER thats helps a lot.

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