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Why do I get different power levels on the GSS7700 / GSS8000 compared to the STR4760?


Design differences between the GSS7700 and STR4760 simulators mean that the MON/CAL power level on the GSS7700 is about 10 dB different from the MON/CAL power level on an STR4760. This difference is also noticeable when referring to the "Offset" cal figures required during power calibration for the STR4760 verses the GSS7700 / GSS8000. However, all simulators provide the same output signal level from the calibrated front RF port.

The STR4760 and GSS7700 are inter-operable and can be used together in a multibox configuration. If you are using a system with both types of simulator where the RF combiner unit has been provided and calibrated by Spirent then the difference in MON/CAL port powers from the two simulator models will have been accounted for to ensure the front RF output port of the combiner unit provides the correct, calibrated signal level (as well as adjusting for RF signal timing differences).
Otherwise you must manually compensate for the different signal levels from the MON/CAL ports. A simple approach, when the two units are used for a multi-antenna differential test set-up. is to use the software power level sliders to apply a relative offset to all channels on one simulator (you could use a user actions file to make the offset a permanent feature of the scenario). Alternatively set up an antenna pattern which has an attenuation/gain of 10dB for signals simulated by the one simulator.
To account for the different in RF signal timing, as a rule of thumb, the GSS7700 RF timing will lag behind the 4760 with a difference in the order of ~380ns.

The STR4760 and GSS8000 are not inter-operable and therefore knowledge about the power differences at the MON/CAL port of the two simulator models will only be of importance to those customers who're upgrading from an STR4760 to a GSS8000.

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