PRAXSYM t-meter, Руководство пользователя

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Measuring VSWR of Antenna and Termina-
tions
To measure the VSWR of an antenna, place the meter into the system
between the transmission line and the antenna. Use the “FORWARD
SIGNAL” arrow on the meter to orient the meter properly. The arrow
will point towards the antenna when it is properly inserted. The dou-
ble male type “N” adapter can be used if the antenna has a female
type “N” connector.
Apply power to the transmitting device. The meter will display the
VSWR so long as there is sufficient power reaching it (between 0 and
20 dBm). In other words, if the transmit power of the radio minus
the transmission line loss is less than 0 dBm, the meter will read
“Below Range”. Likewise, if for some reason the power at the meter
exceeds 20 dBm it will display “Exceed Range”.
The best return loss* that the meter can read accurately in any of the
bands is roughly 20.8 dB. This correlates to a VSWR of approximately
1.2:1. Most antenna manufactures in the license-exempt broadband
wireless market advertise a VSWR of 1.5:1. Therefore, a defective or
damaged antenna feed should be pretty evident using the t-meter, as
they will indicate a VSWR higher than 1.5:1.
It is possible to measure the VSWR (or return loss) of a transmission
line termination by placing the meter between it and the radio. It is
necessary to properly terminate the far-end termination with the 50
Ω termination, and typically a type “N” double female adapter (not
included). These measurements are often only accurate for the ‘local’
terminations, or the terminations that are physically close to the me-
ter. The two-way transmission line loss may mask any reflections
further down the transmission line or at the far-end terminations (i.e.
make the VSWR look better than it really is). The problem becomes
more pronounced as the two-way loss of the transmission line ap-
proaches the dynamic range of the meter, which is 20 dB. Therefore,
it is best to have as little transmission line loss as possible when at-
tempting to measure return loss or VSWR of a termination with the
meter. A VSWR vs. return loss table is included in the Appendix.
NOTE: Reflections are usually due to bad terminations, kinks in the
transmission line, bend radii which are too tight, or moisture in the
line or connectors.
*Return loss is simply the forward power minus the reflected power.
BROADBAND WIRELESS POWER METER
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