I've noticed that the enclosure of my HP 4342A Q meter can seriously degrade the Q of a physically large coil. I wrote a Windows program that lets you extend the meter terminals with a parallel wire transmission line. You suspend the coil a foot or more above the enclosure, run parallel wires to the meter terminals, and record Q and capacitance. The program solves the telegraphers equation and provides the coil inductance and Q as if no transmission line were present. It uses the Getsinger equations to account for transmission line end-effects. Results for a small coil with no enclosure interaction with and without terminal extension were very close.
The program is part of the Q meter utilities listed in the middle of the following page. Another utility compensates for the Q of an auxiliary capacitor used to extend Q meter range. It calculates the Q the meter would indicate if the auxiliary capacitor had no loss. See the end of the page for downloading instructions.
Brian
