You realize the yellow inductors you bought off ebay are not iron cores but probably ferite because 40 turns is equal to + 70uH. Or when you realize your LCR meter is a giant pile of gimp shit and will not measure a value of inductance lower than 10uH. It has been one of THOSE days in homebrewing and so now I am making a test jig to use with the signal generator and oscilloscope to measure the value of the inductors I am winding with some level of accuracy and then getting confused about how accurate the measures will be because inductance changes with frequency and and all that. HIHI. The life of the unwitting, the unknowing and the down right confused.
EDIT: the yellow inductors are most likely type 26, yellow and white. The inductance values I am getting for a given number of turns would suggest this is the case. Type 26 is not much use in RF, good to 1mhz.
Robert,
not sure what your test jig is but I get terrific accuracy with mine. I calibrated my digital capacitance meter so the capacitance of my test jig is probably known within 1%. Since we know the frequency from the signal generator to much greater precision than 1% I expect the inductance measurement from your jig will be as good as the error of your capacitor. Once you’re measuring your inductor at RF you have removed most of the frequency dependant errors too!
So don’t despair. You’re about to learn a technique that never fails!
Regards
Richard
LOL Yeah, its all learning curves. I would not normally worry about measuring inductor values, just wind the right amount of turns and hope for the best. But seeing that I am actually putting in some effort to the superhet rx, I want to be very measured and accurate with everything that I do, so i have benchmarks that I can use for future improvements.
Oh and the frustrating thing about my LCR meter, it was advertised as having good specs on inductance measurement, 2 decimal places at 1uh HEHE, China Ebay Sellers and their imaginary stats.I dug out an old meter i have here, its resolution is 200uh range 1 decimal point, but I am still going to make the test fixture and use the scope, so that i have a comparison. And building your own test gear is good for you. HIHI