Gary Schafer wrote:
. . .
The length of the 50 ohm line is 9 ¾" from shielded area to shielded
area (not counting the center pin exposed when shell is pulled back).
With the barrel installed it makes it 10 ¾" in length that is
shielded.
. . .

By my reckoning, a free space quarter wavelength at 145 MHz is 20.335
inches. Assuming solid polyethylene dielectric coax, this would be about
13.4 inches of coax. 10-3/4 inches would be about 72 degrees.

The probes have a shunt C of 2.5 pF, resulting in a Z (-X) of about 440
ohms at 145 MHz, not 100k ohms. If you parallel that with 50 ohms and
terminate a 72 degree 50 ohm cable with it, the voltage delay in the
cable is 78 degrees -- that is, the imperfect termination actually
increases the cable delay by 6 degrees. If the cable Z0 is 45 ohms
instead of 50, the delay is a couple of degrees less with that load; if
it's 55 ohms, the delay is a couple of degrees more. Maybe your 50 ohm
termination isn't quite what you think it is -- as you can see, it
doesn't take much to substantially change the cable's delay.

As I've said often, most people don't realize how difficult it is to
make accurate RF measurements.

Roy Lewallen, W7EL