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For the convenience of users, the system will automatically display the relevant
information (the maximum allowed cable length: Dmax; resolution Δ D) in the
upper right corner.
For example: N =
corresponding Dmax is 17.64 meters, Δ D is 0.03 meters;
Do not change the frequency, if users want to increase the allowed cable length,
can increase the number of measuring points, the corresponding test time can
also be longer.
NOTE:
Due to the calculation of DTF, the minimum frequency interval is (N-1)
*100 kHz. If the measurement points is 551, corresponding minimum
frequency interval is 55 MHz.
The minimum distance interval is 1 meters (inch) or 1 feet (inch).
Start distance range is: 0~Max-1; stop distance range is 1~Dmax.
4.2.2
Set Cable parameter
Users can manually input cable parameters (velocity; cable loss) or select the
type of cable known.
The propagation velocity of electromagnetic wave in the cable is less than the
vacuum speed (300M meters /second). Propagation constant is 0.85, meaning
that the actual propagation velocity of the electromagnetic wave in the cable is
the 0.85*300M meters / second.
When the user in the fault distance analysis, often want to know the return loss
or VSWR of one exact connector. At that position, the cable loss and connector
return loss will be mixed together, systems need to remove cable loss impact in
the calculation connector return loss. The unit of cable loss is dB/ meter.
Users can select cable from pre-defined cable list. Usually the cable loss will vary
with frequency .System will automatically calculate the cable parameters
According to the cable parameters and working frequency.
If the user does not know any cable information and parameters, but have a
cable at hand, users can use the system tools ("cable" cal) to get these
parameters.
Click on the "cable cal" button in the DTF parameter interface, system will pop up
one window. Users enter the measured actual length of cable (0.5~10 m); one
end of the cable is connected to the RF port, the other end connected to open
load or connected to nothing. Once the calibration is completed, the cable
parameters will automatically refresh in DTF parameter interface.
April 2016
551; Vp =
0.85; F1 =
25 MHz, F2 =
4000 MHz. The
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