I'd like to first give another vote of thanks for this improvement, and also an extra thank you for listening to the users and giving us back the ability to select no filtering.
With that being said, I do have some questions about the new filter settings.
I don't see much documentation on the filtering, so I'm going to try to make some assumptions, and I'm sure I'm wrong!
The settings are loosely documented as a RF HPF, or High Pass Filter, with settings as Normal (HPF), Inverted (which I assume translates into a RF LPF (Low Pass Filter), Auto (which tries both a HPF or LPF until a signal is heard), and OFF, which is no filtering. This to me seems to make sense.
It sure would help to have a clear understanding to specifically what the terms "Normal" and "Inverted" and what they change. I know they are loosely defined as a RF High Pass Filter and an Inverted HPF. But high pass of specifically what HPF of all frequencies above the desired RX frequency? Or HPF of frequencies above a desired RX frequency but in an 8 MHz window?
With the above understanding, I assume what "Normal" would place a HPF starting close to, or just about the desired listening frequency. I believe it's been stated that the internal single 'chip' receiver has a default bandwidth of 8 MHz? So the reason for the Normal/Inverted selection is to help mitigate potential interference, depending if said interference is above or below the desired receiving frequency.
In my case I have a very nearby strong pager transmitter on 152.600 MHz. There could be others also, but this one is almost constantly transmitting.
Using the local WX frequencies to test as it's a fairly constant signal, I tested with the filtering set to Normal, Inverted and OFF.
162.450 MHz with Filter OFF signal is -98dBm, Filter Normal is -60dBm, Filter Inverted is -60 dBm
162.400 MHz with Filter OFF signal is -103dBm, Filter Normal is -99dBM, Filter Inverted is -99 dBm
So for this particular combination I didn't see a large difference between Normal or Inverted, but performance is definitely better than OFF. Perhaps these frequencies are far enough away from the 152.600 MHz pager transmitter so that Normal and Inverted give about the same results?
Is my assumption on how this works wrong? Because if I was trying to listen to any particular frequency, I would think that I may need to have my filter set to Normal or Inverted, depending on if my desired RX frequency was above or below any potential interfering strong signal(s).
With this in mind, I would expect in Sentinel to be able to set the filter choice per 'channel' or 'site frequency.
I can't find how to do this on a per Channel/Site (frequency) in Sentinel. I see the filter option on "Options" per department (group of frequencies) which affect all channels listed, but not for each Channel (frequency). Am I missing something?
Hopefully I don't have some of the Sentinel terms wrong, but the net result is the same, how can I set the filter per frequency or was it not intended to work this way?
Thanks for any help!