TX works at 433 MHz and sends a burst of 64 bytes every second. The burst itself lasts for 102.4 ms. The width of TX signal is 400 kHz.
RX is an Spectrum Analyzer (R&S FSL6) with a receiving antenna. RBW is 100 kHz, VBW is 300 kHz, span is 6 MHz, sweep time is 2.5 ms. "Max hold" is used to obtain the peak value of the received signal.
It is observed that (1) background noise level would rise ~10 dB once "Max hold" is selected: normal -70 dBm, max hold -60 dBm (no additional changes to SA settings) (2) If not read immediately after "Max hold" is selected, peak value would keep increasing gradually.
Questions:
What is the "valid period" for readings in "Max hold" regarding the burst signal? [From the comment, "Max hold" is regarded as valid eternally.]
Based on the settings, did the SA sweep too fast or too slow? Could this be the reason for non-eternal "Max hold" reading?
Is it normal to have the spectrum/noise level risen upon selecting "Max hold"?