170KHz LC Oscillator vs Plain BNC Anomaly. Please Help.

[Mechatrommer]

or let me just put the whole story here in 1K worth of words...

[vk6zgo]

The green & brown caps are polyester.

 Don’t use the electrolytic, they are notoriously inaccurate in value, plus they are lossy (ESR).

I am a bit puzzled by your last posting, but looking back to the one on 26 April, if you calculate the

value of the C, assuming the L is correct from: - fr=1/2pi sqrt LC, for f=526kHz, the cap comes out as 915.52pf, which is within 10% of the nominal value, &

assuming C is correct, that L is 91.552uH, again within 10%.

As capacitors & inductors are not specified to better that, you have done well!

Real components don’t behave quite the same as the perfect versions of theory, for instance, inductors have capacitance between the adjacent turns, as well

as series resistance.

All real components exhibit stray capacitance to earth & other circuit parts.

Even resistors, which are easy to test at dc, don’t look quite the same at 500KHz, & are even more unlike the dc model at, say, 50MHz.   

VK6ZGO

[Mechatrommer]

As capacitors & inductors are not specified to better that, you have done well!

not until i changed capacitor type. and it was suppose to be 1nF and 100uH, but during calibration, it calculated as 0.9++ - 1++ nF and ~87uH, the inductor is off by 13%, i dont know, after latest mod with 442pF (470?), it read wrongly as 2pF (latest picture), but L stays at 87uH, its puzzling i kind of lose track already about the value and mod shown above, still working on it. i got no issue with inductance measurement so far, only variety of type of caps gave inconsistent/conflict reading. My next stop will be to look closely at capacitor and inductor model, and study that. I'll put this circuit on hold until i got stronger background knowledge. Trust me, its more puzzling than it may seems, not a simple words can describe that. The day i'm satisfied with it, the next day i figure out another problem, as Dave said, hopefully your project wont work the first time.