Hi
I found that a coil with a relatively small winding capacitance may not be accurately measured with the proposed method above.
For a 3.9 uH coil with a diameter of 27.5mm, wire diam. 1.5mm and coil length about 27mm, the method above yielded a resonant frequency of 48 MHz whereas the actual self-resonance of the coil is closer to 55 MHz. The reason for this is that we are measuring a parallel-tuned circuit with a relatively small capacitance and any measurement related parallel capacitance will limit the measurement accuracy.
It is therefore probably more advisable to measure the coil resonance in such cases by using a 1-turn coupling loop on the FA-VA5 and coupling to the coil to be measured. The swept SWR measurement will show a small dip at resonance. See image below.
73
Dieter, VK3FFB
Dieter VK3FFB
