The APF button enables diversity mode on the PCR2500 receiver and selects the best antenna for the frequency. Antenna 1 are currently a Sirio 5/8 GP @125MHz and antenna 2 are a Diamond X510. It only works in FM and NFM mode and other modes will only use antenna 1.
I have a 30 meter wire tuned to the 80m band connnected to the antenna1 coax that seems to have some reception of shortwave. It worked beautifully for a day then the BFO quit. So no CW USB or LSB are functional but AM seems to work as normal. My filters doesn't pass anything except QSB below 500KHz.
I sometimes alternate between antennas with a TV antenna 80-700MHz AV-860B and a Diamond F23 VHF @155MHz and a Diamond X510 dualband 144/433MHz modified for scanner use and also a 13dBi 420-460MHz InnovAntennas 17-element yagi. If directional the antennas point west into Stockholm city. The yagi are now mixed into the X510 coax to get additional UHF coverage.
My antennas have amplifiers and splitters to support other scanners. I usually have a FM trapfilter inline that makes FM broadcast more difficult to monitor, but almost all of them are broadcasting on the internet.
https://streema.com/radios/Stockholm
The antennas are at 25 meters above sea level in a valley surrounded by 50 meter high hills so it is a terrible qth for monitoring the radio waves.
The frequency list for my area are at
https://www.frekvenslista.com/lista.php?city=®ion=1&Submit=Uppdatera