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.
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"?