> I would think you at least need a diode detector and sweep the loop. Thanks Mike, I'll give that a go, as my audio generator goes up to 100 kHz. and I've got a high input Z digital voltmeter to look for the peak. 73, J.B., VE3EAR LowFER Beacon "EAR" 188.830 kHz. QRSS30 EN93dr