This is regarding the selection of best RBW for spectrum analyzer (PXA).
Span is 1GHz, number of sweep points 10001. I think PXA has 1001 display points or pixels.
In this case, bucket size is 100 KHz(1GHz/10001). RBW of 100 KHz will cover one bucket and 1 MHz will cover 10 buckets. Which is better RBW of 100 KHz or 1 MHz?. Or what is the logic for selecting best RBW?
I'm not sure what the bucket sizes are but I can help with the question of logic of selecting the bandwidth setting. The best bandwidth is the one that will resolve the signal you are interested in. This varies depending on the type of signal and several other factors.
Here is a video that may help you on how to select the best Resolution Bandwidth for your measurement. This is a Keysight YouTube channel.
https://www.youtube.com/watch?v=dStvdC9mhJ4
Hope this helps,
Gary