Operating Instructions
3-1
10 TEGAM WAY ● GENEVA, OHIO 44041 ● 440-466-6100 ● FAX 440-466-6110 ●
3.
T
HEORY OF
O
PERATIONS
Traceability
The GEMINI RF Power Meter is traceable to the International System of Units (SI) through
the National Institute of Standards and Technology (NIST) or other recognized National
Metrology Institutes. This is accomplished through comparison to TEGAM’s high-power RF
calorimetric system maintained in TEGAM’s laboratories, itself traceable to the SI.
Measurement Theory
The GEMINI RF Power Meter is based on custom-designed directional power sensors coupled
to a high-frequency, high-power transmission line internal to the instrument. Forward and
reverse couplers react to the power flowing in the corresponding direction in the transmission
line. This measurement data is used to calculate forward and reverse power. A third coupler
is used to determine the frequency.
VSWR Calculation
VSWR is calculated from the forward and reverse power measurements. It should only be used
for reference. As power is proportional to the voltage squared, VSWR can be derived from
these power measurements with the following formula:
Where either the forward or reverse power readings are outside the dynamic range of the
instrument, the display will indicate
INVALID
for VSWR.
Maximum Rated Power
The GEMINI RF Power Meter maximum rated power is frequency and connector dependent.
See Appendix C for typical power limits of various connector configurations. For specific power
levels and calibration frequency points, see the Certificate of Calibration for the particular
GEMINI RF Power Meter.
