[time-nuts] Non-impedance matched antenna cables
phil
fortime at bellsouth.net
Sat Jun 14 06:02:10 UTC 2008
I know you guys like to drill holes through hairs, but ....
As I follow the discussions on merits of 50/75 ohm cable, cable length
changing with ambient temperature, tuning cable to a fraction of wavelength,
power supply noise etc.
Does not the "weakest" link determine it's best accuracy? If so, the
receiver/electronics and internal programming seems to be the weakest link
and all these small nano/pico second variables discussed seems moot, at
least with unit in question.
If your receiver for example computes your location with a rather large
error in lat/lon or altitude, that error I would think would be greater than
the sum of all the "small" factors/errors being discussed. I have found, at
least with the Thunderbolt receivers I have used, they are rather sloppy in
it's location fix but even worse in it's altitude fix.
As I understand it, each foot of distance is a little over a nanosecond in
delay so would not position/altitude accuracy be the biggest variable, not
to mention the proper calculation and offset of antenna cable
attenuation/length.
I would be curious how the older Thunderbolt units compares to a newer
technology receiver/timebase in the "real world".
Just a thought
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