Yes, weak coupling of the oscillator under test to a small nearby antenna connected to a sensitive receiver is the way to tune those touchy circuits.
The receiver can be calibrated to WWV on 10MHz and 5MHz, then it is easy to get 1Hz accuracy.
I am using Airspy HF+ Discovery and HDSDR software, but other SDR HW/SW combination would work, too. Preferably ones with a TCXO, so you don't need to re-calibrate often.
My "antenna" is a 5cm central wire sticking out of an SMA male connector. The shield is stripped away.
73, Mike AF7KR
