Cecil Moore wrote:
Jim Lux wrote:

I should think that many hams have things that can measure 3 ns
(1000mm light time), particularly in a repetitive system. That's one
cycle at 300 MHz, or 36 degrees at 30 MHz.


The referenced W8JI 3 nS "measurement" was the delay
in a 2' dia, 100 T, 10" long loading coil on 4 MHz,
i.e. 4.5 degrees.


4.5 degrees is easy to measure at 4 MHz with a variety of systems.

Basic measurement theory says that the phase measurement uncertainty is

uncertainty in radians = 1/sqrt(T * Psig/No)
where T is the integration time, Psig is the signal power, and No is the
noise spectral density (W/Hz)

Let's throw in some numbers..

Psig = 1 mW (1E-3W)
No = -160 dBm/Hz (kTB noise + 14 dB)
T = 10 millisecond

uncertainty = 1/sqrt(1E-2 * 1E16) = 1 / 1E7 = 1E-7 radian

1 degree is about 0.017 radian, so I think you wouldn't have much
problem measuring the phase shift, from a physics standpoint.. all a
matter of experimental technique..

Anyway, there are LOTS of ways to do the measurement, most of which
would require only things that hams have sitting around, with a few
hours of cobbling together.