I'm not sure that is even possible....
It is hardcoded now so it can be simple and optimized. Triggering is realtime operation running of full speed datastream.
I think it may be possible to be added as a feature because the hardcoded frequencies 1. don't match (internal vs. external), and 2. aren't standard filter numbers like for the channel filters. It seems they were chosen at least somewhat arbitrarily and should be able to be replaced with a variable input. Or, a new trigger coupling filter with a variable input added, but that would seem redundant.
Thanks,
Josh
ETA: Check out nctnico's post with channel filtering: https://www.eevblog.com/forum/testgear/new-keysight-infiniivision-hd3-oscilloscope/msg5663417/#msg5663417
That would be nice too. 😉
Nico's post has nothing to do and don't confuse it with channel filtering.
HP and LP filter in trigger works on full data rate and it is at it is because filter was chosen that was fastest and it landed approximately where it did.
As for filters in math, they are have current characteristics because of number taps in implementation. As Martin said, it is similar to LeCroy in that regard.
Other manufacturers did something else, and they are either decimating or use some nonstandard filtering method. Siglent uses proper FIR filters.
Filter on Keysight 3000T can filter lower frequencies with same sample rate, but it's characteristics is not documented at all and it is basically visual aid.
Micsig I have also have limits when sampling at higher sample rates.
Do not get me wrong. I will raise this question with Siglent. I personally would like if filters on Siglent scopes would be more powerful. But maybe this was resource limit? I don't know.