>> http://www.aade.com/freqstd/freqstd.html I can second that item... I bought one several years ago, I calibrated mine to less than 0.1 cps at 10MHz. Using a 9V battery and a 5 minute warm-up, it has maintained its calibration to date. There is a multi-turn pot on the PCB for fine tuning - Dave G, KK7SS '65 MKIII Sprite, Richland, WA