Nothing original here but I found this information so hard to track down on the web when I was looking for it that I thought I’d duplicate on my site with some images to enhance people’s chance of finding it. Really, all is explained on Dean Gibson AE7Q’s page. Thanks Dean.
The Yaesu FT-857 and 897 series radios support the installation of optional filters, primarily Yaesu’s own YF-122S (2.3kHz), YF-122C (500Hz), and YF-122CN (300Hz) Collins ceramic filters but alternative filters are available from other suppliers e.g. Inrad. After reading reviews of alternative filters, I decided the Inrad 2.0 kHz filter might suit my needs for the FT-857D to reduce interference from strong adjacent signals to SSB reception. The PCB module that the Inrad filter is supplied mounted on (if you choose the FT-857/897 option) is detected by the radio as a 2.3 kHz filter and shown as such on the radio’s display:
By making a link across solder pads on the filter PCB it no longer appears to the radio as the 2.3 kHz filter and the filter is shown as “FIL1” or “FIL2” depending on which slot you fitted it to:
Finally, adjusting Menu item no. 64 (in the same way as memory names are entered onto the radio, press Select knob, rotate Select knob to select character, rotate VFO knob to adjust character, press Select knob to exit) allows you to rename the custom filter to your preference, in my case “2.0”: