Deepace KC901V Manual page 27

There are two items in FUNC menu, which are "Cable Length" and "Cable Loss".
Cable length is the actual length of the cable divided by the velocity coefficient. With
cable length, cable loss can be predicted according to the loss per unit length which is
provided by cable technical manual.
Both two items above are the one way travel parameters.
The operation of cable canceling is only suitable on low frequency, under 30MHz.
Only in this condition, user should try to do the user calibration on the cable which is
far away from the instrument so that the instrument can remove the cable influence
preciously.
4.2.3 Antenna Impedance Measurement
KC901V can calculate antenna's impedance by testing RF signal, amplitude dif-
ferences of reflection signal and the phase differences. Since amplitude and phase
differences are related with the feeder line, the user calibration must be done on the
end of the feeder line unless the antenna connects to instrument directly.
About the antenna of the PCB, if there is no coaxial interface, user can discon-
nect the antenna from the PCB, and then connect the small coaxial cable to the in-
strument. perform calibration before any measurement. When the instrument
prompts user to do open/short circuit, open/short circuit the end of the coaxial cable
accordingly. Then skip the load calibration (SKIP).
Antenna's installation environment has a great influence on antenna's imped-
ance. So during the measurement, make sure the antenna system setup is as close as
the application environment. For those antennas which are installed on handheld de-
vice, routers and other devices, since they work together with other devices' metallic
conductive casing, the case must be included into the measurement. For example, if
router's antenna needs to be tested, router ant's host device case should be tested
together. The original coax need to be disconnected from router's PCB, and then
route the testing cable for antenna. The end of the testing cable, which is near the
antenna, needs to go through the toroid ring. During the calibration, make sure that
this cable is included.
Under the low frequency, if it's not able to do the calibration on the cable, user
can set cable length in FUNC menu to remove its influence. When the frequency is
high (for example, 2400MHz), this way is not reliable.
4.2.4 Simple Measurement of Antenna's Gain and Antenna Pattern
KC901V can test antenna's horizontal pattern or the front-to-back ratio by using
its S21 (or insertion loss) function with another set of antenna; If there is another set
of antenna which the gain is already known, then the antenna gain can be tested too.
Measurement environment: RF anechoic Chamber or standard measurement
site. For engineering measurement, choose a place which is an open and level ground.
Suggested size is bigger than 20 times of the wave length. For antenna which the fre-
quency band is over UHF, flat root can be used.
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