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Trouble Shooting Guide, Advanced
10.2 How to measure the transient spectrum
GSM 900:
Give the board power and start it in the test program.
Start the transmitter in switched mode at channel 64 and power level 5.
Before performing a transient spectrum measurement you have to make sure the spectrum
analyser has got the correct amplitude compensation.
To do this you use a phone with a known output power and start the transmitter in static mode at
power level 5.
Then you compensate the spectrum analyser until the correct output power is achieved.
Convenient settings for this are:
CF – 902.8 MHz, SPAN – 0 MHz, RBW – 300 kHz, VBW – 100 kHz and SWEEP – 0.8ms.)
One method to measure the transient spectrum is to use the following settings at the spectrum
analyser:
CF – 903.2 MHz, SPAN – 0 MHz, RBW – 30 kHz, VBW – 100 kHz and SWEEP – 6 ms.
You measure the highest level of the signal.
The easiest way to do it is to use "single sweep" to freeze the picture and "peak search" to find
the highest level.
The spectrum should look like the figure below Fig. 10.3.
Fig. 10.3
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